CAR Flashcards

Question

functions of the cardio-respiratory system

Answer 1

Transport – to and from metabolising tissue Oxygen and carbon dioxide Nutrients Waste Heat Hormones Homeostasis pH, osmolarity, electrolytes etc Infection Other Generate pressure (eg renal filtration)

Answer 2

Disease usually involves valve degeneration, and the valve becoming incompetent or diseases of the heart muscle, resulting the heart not contracting well OR not filling well

Answer 3

volume delivered into the circulation per minute volume delivered by the ventricle per beat

Answer 4

Heart failure is a syndrome in which the heart fails to deliver blood effectively to meet the requirements of metabolising tissues

Answer 5

Ventricular systole = contraction of ventricles Results in cardiac output Atrioventricular valves close The source of the first heart sound – “Lub”

Answer 6

Important controlling factors: Sympathetic nervous system Blood volume Muscle (respiratory) pump

Answer 7

process by which deoxygenated blood is returned to the heart

Answer 8

portal veins are found between two capillary beds (site of diffusion)

Answer 9

echocardiography

Answer 10

look at the labelled version

Answer 11

renal portal valve

Answer 12

Receives blood from caudal body and returns it to the heart via the kidneys

Answer 13

look at answer

Answer 14

Simple cardiovascular system “2 chambers” to the heart Blood flows in one direction effectively through a single atrium and ventricle (technically there are 6 chambers similar to the primitive tube) Vasculature includes gills to accommodate oxygenation Heart is often positioned ventral and caudal to the gills

Answer 15

In anurans we start to see 2 atria – 3 chambers in total Oxygenation occurs from lungs, skin and buccal cavity hence vasculature more complex compared to mammals Heart is mid cranial coelom Like birds they have no diaphragm, hence the term coelom again

Answer 16

Most reptiles have 3 chambers, with 2 atria and 1 ventricle. The ventricle is split into 3 sections by folds in the muscle wall Crocodiles are an exception with 4 chambers but distinct differences from mammals still (2 x aortas) All reptiles can shunt blood away from the respiratory tract when needed. For most species the heart is mid cranial coelom, some very cranial (base of the neck). For snakes the heart is often found in the cranial third of the body.

Answer 17

Transport – to and from metabolising tissue Oxygen and carbon dioxide Nutrients Waste Heat Hormones Homeostasis pH, osmolarity, electrolytes etc Infection Other Generate pressure (eg renal filtration)

Answer 18

Heart failure is a syndrome in which the heart fails to deliver blood effectively to meet the requirements of metabolising tissues

Answer 19

systole and diastole respectfully

Answer 20

Ventricular systole = contraction of ventricles Results in cardiac output Atrioventricular valves close The source of the first heart sound – “Lub”

Answer 21

Ventricular diastole = relaxation of ventricles Results in ventricular filling Semi-lunar valves close The source of the second heart sound – “Dub”

Answer 22

regulation of cardiac function and regulation of the vasculature. Regulation of cardiac function Need to consider: Can change heart rate and contractility Electrical activity (Electrophysiology) Assessment of this using an ECG Contractile function control The important role of the autonomic nervous system Hormonal mechanisms (local and systemic) Regulation of the vasculature Autoregulation - local blood flow regulation, intrinsic ability of an organ to maintain a constant blood flow despite changes in perfusion pressure. The important role of the autonomic nervous system Hormonal mechanisms (local and systemic)

Answer 23

the strength of contractions

Answer 24

Cardiac Output (volume delivered into the circulation per minute) Stroke Volume (volume delivered by the ventricle per beat) Other pumping mechanisms (venous) ….and what control these

Answer 25

Vascular constriction and dilation – arteries AND veins The maintenance of unidirectional flow in vital organs Cardiac valves Vascular valves

Answer 26

Is the amount of blood pumped per minute

Answer 27

Sympathetic nervous system Blood volume Muscle (respiratory) pump

Answer 28

between 2 capillary beds

Answer 29

look at answered version

Answer 30

Main features of the avian CVS: 4 chambered heart similar to mammals mammals AV valves are different in structure compared to mammals The heart is located within the cranial ventral coelom and is surrounded by air sacs Term coelom is used because birds don’t have a diaphragm

Answer 31

By increasing heart rate (115-670BPM)

Answer 32

they increase prior to migration in migratory species

Answer 33

Ventricles Left sided ventricular wall 3x thicker than right Empty almost completely on each cardiac cycle Low end-systolic volume

Answer 34

Reptiles, birds, amphibians and most fish – not in mammals Receives blood from caudal body and returns it to the heart via the kidneys It functions to supply blood to renal tubules at all times Portal blood flow regulated by renal portal valve. Alters how drugs will act in these species: for example if injected in caudal half of the body then maybe metabolised before entering general circulation

Answer 35

Look at labelled version

Answer 36

Look at the labelled answered version

Answer 37

Simple cardiovascular system “2 chambers” to the heart Blood flows in one direction effectively through a single atrium and ventricle (technically there are 6 chambers similar to the primitive tube) Vasculature includes gills to accommodate oxygenation Heart is often positioned ventral and caudal to the gills

Answer 38

In anurans we start to see 2 atria – 3 chambers in total Oxygenation occurs from lungs, skin and buccal cavity hence vasculature more complex compared to mammals Heart is mid cranial coelom Like birds they have no diaphragm, hence the term coelom again

Answer 39

Look at the answer version

Answer 40

Most reptiles have 3 chambers, with 2 atria and 1 ventricle. The ventricle is split into 3 sections by folds in the muscle wall Crocodiles are an exception with 4 chambers but distinct differences from mammals still (2 x aortas) All reptiles can shunt blood away from the respiratory tract when needed. For most species the heart is mid cranial coelom, some very cranial (base of the neck). For snakes the heart is often found in the cranial third of the body.

Answer 41

Transport - Delivers O2 from lungs and nutrients from digestive system Removes waste, heat and CO2 from tissues Hormones Protective function – carries WBC and Ig Homeostasis – pH, ions, fluid volume Pressure

Answer 42

Look at answered version Kidney renal artery to the glomerulus, efferent arterioles takes oxygenated blood to the kidney tissue

Answer 43

0.75% - relatively larger in smaller animals

Answer 44

Ventral border of the lungs Cardiac notch (L>R) Lungs laterally Phrenic nerve Thymus cranially Diaphragm caudally

Answer 45

produces and trains t-cells

Answer 46

motor innervation to the diaphragm

Answer 47

Look at completed version

Answer 48

in mediastinum (The mediastinum is a space in your chest that holds your heart and other important structures) 60% is to the left of the median plane

Answer 49

Apex sits in sternum – costochondral junction 6 Right ventricle is CRANIAL to left! Base is dorsal Ribs 3-6

Answer 50

groove that splits the atria from the ventricles. It is also where the coronary arteries sit in Paraconal and subsinuosal groove mark where the septum is. Pulmonary artery is on the right side. Paraconal groove cranially Subsinuosal groove caudally

Answer 51

Sac surrounding the heart Inner visceral layer on surface of the heart Outer parietal layer No significant lumen

Answer 52

Intervenous tubercule diverts blood into the atrium.

Answer 53

cranial and caudal vena cava, intervenous tubercle sits in the middle of these at the point at which they meet It brings blood back from the thorax

Answer 54

Trabecula septomarginalis (also known as the moderator band) ensures communication is quick on both sides found in the right ventricle

Answer 55

2 cusps Chordae tendiae - papillary muscles

Answer 56

R semilunar - pulmonic L semilunar - aortic 3 cusps

Answer 57

When pressure in ventricles exceeds that of aorta and pulmonary artery

Answer 58

The myocardium is the middle muscular layer of the heart, situated between the inner endocardium and the outer epicardium. Also known as the cardiomyocytes

Answer 59

The outer layer of the heart wall that protects the inner layers and produces pericardial fluid. Also known as the visceral pericardium

Answer 60

The endocardium is the innermost layer of tissue that lines the chambers and valves of the heart. It is composed of a thin, smooth tissue that serves as a barrier between the cardiac muscles and the bloodstream, ensuring efficient blood flow.

Answer 61

Large, cylindrical cells Striated (myofibrils) – like skeletal m. Short, branched fibres Lots of mitochondria

Answer 62

Connect adjacent cardiac muscle cells. Allow for Cell-to-cell communication Required for coordinated muscle contraction

Answer 63

Specialised conducting tissue Deliver electrical activity to myocardium

Answer 64

Sympathetic nervous system Preganglionic neurons are relatively short and originate from the thoracic and lumber regions of the spinal cord. Postganglionic neurons are relatively long and extend from the sympathetic ganglia to the target organs Parasympathetic nervous systems Preganglionic neurons are relatively long and originate from the brainstem and sacral (relating to the sacrum a triangular-shaped bone at the base of the back) regions of the spinal cord Postganglionic neurons are relatively short and extend from the parasympathetic ganglia to the target tissues.

Answer 65

Nicotinic acetylcholine receptors. Worked on by acetylcholine, designation is cholinergic

Answer 66

alpha and or beta receptors. Acted on by adrenaline (epinephrine) and its designation is adrenergic

Answer 67

alpha and beta receptors. Noradrenaline (norepinephrine), adrenergic

Answer 68

muscarinic acetylcholine receptors, acetylcholine, nicotinic

Answer 69

Alpha receptors stimulate effector cells and are responsible for vasoconstriction and increasing blood pressure. Beta receptors relax effector cells and are responsible for vasodilation and decreasing blood pressure.

Answer 70

Adrenergic receptors are a class of G protein-coupled receptors that are targets of many catecholamines like norepinephrine and epinephrine produced by the blood. Catecholamines are a monoamine neurotransmitter with a benzene group and two attached hydroxy groups (-OH) right next to each other

Answer 71

Muscarinic acetylcholine receptors are a type of acetylcholine receptors that are G protein-coupled receptors.

Answer 72

It is activated in situations that require a fight or flight response, such as stress, physical activity, emergency situations and excitement.

Answer 73

It has a thoracolumbar outflow as the SNS originates from the thoracic (T1 to T12) and lumbar (L1 to L2) segments of the spinal cord.

Answer 74

The ganglia in the SNS are located in specific regions that facilitate the relay of signals from the CNS to target organs. Paravertebral ganglia (sympathetic chain ganglia) are on either side of the spinal column and extend from the base of the skull to the coccyx (tailbone). These are closely associated with the thoracic and lumbar regions of the spinal cord where the preganglionic neurons originate. Prevertebral ganglia are located anterior (towards the front of) to the vertebral column, near major arteries Adrenal medulla acts as a modified ganglion. It releases adrenaline and noradrenaline directly into the blood stream in response to sympathetic stimulation.

Answer 75

look at labelled version

Answer 76

The PSNS is activated during rest-and-digest situations, promoting relaxation, recovery, and maintenance of the body’s homeostasis. Specific circumstances causing this include relaxation, eating, resting and reproductive activities.

Answer 77

For PSNS you have a craniosacral outflow, the PSNS originates in the brainstem and the sacral (relating to the sacrum, a triangular-shaped bone at the base of the back) region of the spinal cord.

Answer 78

The preganglionic neurons of the PSNS arise from the cranial nerves (oculomotor, facial, glossopharyngeal and Nictitans) as well as the sacral nerves which arise from the sacral spinal cord segments S2 to S4 and innervate the lower abdominal and pelvic organs.

Answer 79

In the PSNS, the ganglia are located closer to or within the target organs they innervate. This is different from the SNS, where the ganglia are generally located near the spinal cord.

Answer 80

autonomic reflexes. Autonomic reflexes regulate various involuntary bodily functions essential for maintaining homeostasis. afferent nervous system 1. Heart rate regulation 2. Respiratory rate 3. Digestive processes 4. Pupil dilation and constriction

Answer 81

The 2 primary affects the SNS have on the heart is: Increased heart rate (positive chronotropy) – SNS releases norepinephrine which binds to beta-1 adrenergic receptors in the heart. This interaction increases heart rate by accelerating the rate of depolarization of the SA node, the hearts natural pacemaker. Increased force of contraction (positive inotropy) –norepinephrine binding to beta-1 adrenergic receptors also enhances the force of contraction of the heart muscle. This increases the volume of blood ejected with each beat improving the overall cardiac output.

Answer 82

The SNS has several effects on the lungs, primarily through the activation of beta-2 adrenergic receptors in the bronchial smooth muscles, The main effects:- bronchodilation – SNS stimulates the release of norepinephrine, which binds to the beta-2 adrenergic receptors in the bronchial smooth muscles. This leads to the relaxation of these muscles, causing the airways to widen. Bronchodilation increase the airflow into and out of the lungs, which is especially important during physical activity or stressful situations when the body’s oxygen demand is higher. Decreased secretions –SNS can reduce mucus secretion in the airways, helping to keep them clear and improve airflow. This is achieved by inhibiting the activity of certain glands in the respiratory tract.

Answer 83

Pre-G fibres are relatively short in length Post-G fibres are relatively long in length

Answer 84

Blood pressure receptors. Carotid sinus, aortic arch The carotid sinus, also known as the carotid bulb, is a neurovascular structure that appears as a dilation at the bifurcation of the common carotid artery into the internal and external carotid bodies. It is localized near the arterial pulse. Monitor blood pressure going towards the brain. The aortic arch, arch of the aorta, or transverse aortic arch is the part of the aorta between the ascending and descending aorta. Monitor the blood pressure of the blood flowing through the systemic circulation.

Answer 85

They detect changes in the chemical composition of the blood and other bodily fluids. 1. Peripheral chemoreceptors (carotid bodies, aortic bodies) 2. Central chemoreceptors Carotid bodies are small clusters of chemoreceptors located at the bifurcation of the common carotid arteries into the internal and external carotid arteries. They monitor the levels of oxygen, carbon dioxide, and ph in the blood. Aortic bodies are located near the aortic arch and similarly monitor blood levels of oxygen, carbon dioxide and ph. They are less sensitive than carotid bodies but contribute to respiratory regulation. Central chemoreceptors are located on the ventral surface of the medulla oblongata in the brainstem. They primarily monitor the ph of the cerebrospinal fluid which indirectly reflects the levels of carbon dioxide in the blood. These chemoreceptors play a crucial role in regulating the rate and depth of breathing.

Answer 86

Baroreceptors firing frequency falls, which tells the CNS that BP is low, altered impulse frequency to the effector increasing HR and vasoconstriction, compensatory systems are activated

Answer 87

within the cardiac plexus (network of nerves that innervate the heart)

Answer 88

Controls rate and rhythm, another term for this (=ve/-ve) cardiac regulation effect

Answer 89

Post-G fibres also go to the myocardium  this controls the force of contraction = +ve/-ve intropic effect

Answer 90

Effects are generally opposite to that of the SNS. Negative chronotropy (decreased heart rate), negative inotropy (reduced force of contraction)

Answer 91

Heart- negative chronotropy (decreased heart rate), negative inotropy (slight reduction in contractility) Lungs – bronchoconstriction (narrowing of the airways), increased mucus secretion.

Answer 92

SNS - B2-adrenergic receptors involved - stimulate bronchodilation by stimulation on bronchial smooth muscle, causing relaxation and inhibition of mucous secretion PSNS -muscarinic receptors - stimulate bronchoconstriction and increased mucus secretion - Ach released from vagus nerve endings binds to m3 receptors on bronchial smooth muscle and glands

Answer 93

The cardiac plexus is a network of autonomic nerves located near the base of the heart, mainly around the aortic arch and bifurcation of the trachea. It plays a central role in regulating heart rate, force of contraction, and coronary blood flow.

Answer 94

Pre-G fibres travel in branches of the recurrent laryngeal and vagal nerves to the cardiac plexus. The post-G fibres end in the atrial walls.

Answer 95

Increased sympathetic activity causes an increase in epinephrine in blood and increase in norepinephrine from sympathetic nerve endings. Adrenergic receptors are stimulated and cause an increased generation of cyclic AMP, which causes increased phosphorylation of voltage-gated CA2+ channels and increased phosphorylation of phospholamban. Increased phosphorylation of voltage-gated ca2+ channels cause an increase opening time of the channels and an increase in ca2+ influx from extracellular fluid, which causes an increase an induced ca2+ release from sarcoplasmic reticulum which causes more forceful contraction. Increased phosphorylation of phospholamban causes an increase in transport of ca2+ from cytosol and back to the sarcoplasmic reticulum which causes a shorter contraction time.

Answer 96

90-140BPM for small dogs 60-100BPM for medium to large dogs 120-160BPM for puppies

Answer 97

Heart murmurs are unique heart sounds produced when blood flows across a heart valve or blood vessel. A murmur is an abnormal extra sound, which can sometimes drown out the normal sounds. They most commonly occur between the lub dub and have a shooshing or whooshing quality.

Answer 98

10-20 for larger dogs 20-30 for puppies and smaller dogs

Answer 99

Capillary refill time. This is how long it takes the pink colour to return in your pets mouth. Should be less than 2 seconds

Answer 100

The inflammation of gums.

Answer 101

Turbulent flow causes a heart murmur. So not a calm smooth manner. The turbulence occurs because there is a hole in the heart between two chambers or two arteries that are not normally connected: these are mostly ventricular septal defects. Another cause is narrowing (stenosis) within a chamber or vessel through which the blood has to squeeze through.

Answer 102

The difference lies at the timing of the abnormal heart sounds during the cardiac cycle. Systolic heart murmur– occurs between the lub and the dub noise, during ventricular contraction. Diastolic heart murmur – occurs after the dub noise and before the lub noise, during ventricular relaxation.

Answer 103

aortic pressure

Answer 104

A phonogram shows where in a cycle you can hear the noise of the heart.

Answer 105

S1 closing of the AV valves S2 closing of the semilunar valves (reverberation from the sudden block of flow)

Answer 106

a Wigger's diagram

Answer 107

systole 35%, diastole 65%

Answer 108

Atrioventricular valves closed , semi-lunar valves open

Answer 109

Filling phase (i.e. ‘diastole’) Ventricles fill during diastole (and atrial systole). Isovolumetric contraction phase Ventricles contract, but volume remains constant because the heart valves are closed. Pressure builds. Outflow phase (i.e. ‘systole’) Ventricles contract, valves open, blood into aorta/pulm art. Isovolumetric relaxation Ventricles relax, ready for refill with blood in the next filling phase

Answer 110

systole - isovolumetric contraction, rapid ejection, reduced ejection diastole - atrial systole, isovolumetric relaxation, rapid ventricular filling, diastasis

Answer 111

Last phase of diastole (ECG (electrodiagram) P to R-wave) Depolarisation of the atria leads to atrial contraction (see the ‘a’ wave on the atrial pressure curve). A tiny amount of ‘topping off’ completely fills the ventricle.

Answer 112

First phase of systole Begins at the peak of the R-wave of the ECG No real change in the volume of the ventricles during this phase First heart sound (‘lub’) = closing of the A-V valves, associated blood turbulence when ventricular pressure exceeds atrial pressure

Answer 113

During ST segment When ventricular pressure exceeds that in the aorta or the pulmonary artery, semilunar valves open and rapid ejection (2/3) from the ventricles starts ‘c’ wave in the atrial pressure curve is caused by slight (due to papillary muscles) distension of the A-V valves into the atria (normally not measurable)

Answer 114

- Final phase of systole - Coincides with the T-wave of the ECG (ventricular repolarisation) - Blood flow out of the ventricles continues, but more slowly (hence, ‘reduced ejection’) - Eventually, pressure in the ventricle falls below that in the arteries. Semilunar valves close

Answer 115

- First phase of diastole - Atria have been filling with blood (atop the closed A-V valves) and atrial pressure has been rising gradually - Blood flow out of the ventricles stops (hopefully the ventricles are sufficiently empty) - 2nd heart sound (‘dup’) occurs when the semilunar valves close

Answer 116

- When ventricular pressure falls below atrial pressure, the A-V valves open. - This allows blood to flow from the atria into the ventricles. - sometimes a sound heard – indicative of congestive heart failure ? (atrial press. too high)

Answer 117

Both ventricles contract simultaneously, causing a pressure increase but no change in blood volume in the heart

Answer 118

Rapid Ventricular Ejection

Answer 119

The venous pulse reflects the dynamic changes in pressure and volume in the heart's right atrium and its interaction with venous return

Answer 120

the venous pulse waveform typically consists of three positive waves (a, c, and v wave) and three descents (x, x’, and y descent), each linked to specific phases of cardiac function…pto

Answer 121

Increased venous return elevates right atrial pressure and can exaggerate waveforms. Decreased venous return diminishes the magnitude of the pulses. This interaction highlights the dependency of venous pulses on preload and the heart's ability to manage systemic venous return

Answer 122

c wave- tricuspid valve bulging x descent - atrial relaxation x' descent - ventricular systole v wave - atrial filling y descent - ventricular filling

Answer 123

The venous pulse is a dynamic reflection of the pressure changes in the right atrium caused by the phases of the cardiac cycle. Careful observation of the venous pulse can offer critical insights into cardiac function and potential pathologies

Answer 124

The ventricular pressure-volume (PV) loop graphically represents the relationship between pressure and volume in the left ventricle during a single cardiac cycle. This loop is instrumental in understanding cardiac mechanics, as it delineates the phases of ventricular filling, isovolumetric contraction, ejection, and isovolumetric relaxation

Answer 125

answered version

Answer 126

Arterial pulse will be felt at max ventricular pressure (ejects into arterial network) Venous pulse will reflect atrial pressure (and will not be as obvious)

Answer 127

atria are always filling

Answer 128

An angiogram is a type of X-ray used to examine blood vessels. They don’t show up on ordinary X-rays so a special dye is injected into the area being examined.

Answer 129

fetal circulation labelled version

Answer 130

labelled version

Answer 131

the heart CV system begins when cardiogenic plate of mesodermal tissue develops at cranial end of embryonic disc Blood islands form in cranial end of embryo in early w2. Islands form two parallel vascular tubes which are brought to the ventral side of embryo to fuse to form a single tube as embryo folds. Embryo folding at head (and tail) ends. Cephalic folding brings developing cardiac tube into chest region. Neural tube grows quicker than rest of embryo (especially at cranial end due to brain development) and is fixed at two ends so embryo FOLDS (becoming a tubular embryo) Heart falls to right (D-looping)

Answer 132

- arterial trunk/ truncus arteriosus (origin of the pulmonary artery and aorta) - bulbus cordis form ventricle - ventricle form ventricle - atrium - sinus venosus There are named constrictions. The constrictions later become chambers as the names show. It is formed by the formation of these two tubes on each side that developed in the cardiogenic mesoderm.

Answer 133

Right horn of sinus venosus becomes incorporated into atrial wall Left horn not incorporated – becomes coronary sinus on atrial surface of heart The whole thing sort of twists just not falling to the right. It just twists and twists even more and then the thing fuses together. Look at cardiac looping image

Answer 134

It is initially received from the sinus venosus and goes into the primitive atrium. The endocardial cushions, expand and start to separate of the atria from the ventricles below. The endocardial cushions will also from the valve flaps and chordae tendinea (heart strings). Look at endocardial cushions image

Answer 135

look at interatrial septation image

Answer 136

a newborn baby, particulary during the first 28 days of life

Answer 137

Fetus ‘breathes’ amniotic fluid (not air, as lungs deflated) Therefore pulmonary artery does not carry oxygen it Is not really needed Fetal blood is oxygen-poor (hypoxaemic) This is normal, but haemoglobin is ‘different’ to pick up oxygen at greater affinity at a lower Partial Pressure of oxygen Fetus swims in amniotic fluid Provides a Stable temperature it is buffering Water helps protect from bumps Fetus is fed parenterally (umbilical cord), not orally Therefore hepatic portal vein is not needed

Answer 138

Postnatally the foetus is very fragile, and tissues are fragile you don’t want them under high blood pressure.

Answer 139

The foetus is fed parentally (fed nutrition straight into the veins, not going through the gut, GI tract and is then modified by the hepatic portal vein to the liver. First passes through the liver and sort of screens it. None of this happens in the foetus, it is just delivered into the veins as the maternal circulation and then the placenta screen out anything that you don’t want getting through

Answer 140

Fuel storage/ detoxification in adults fat/muscle/liver Gas exchange in adults lungs Waste removal in adults kidneys/liver lungs and livers: net "receivers" during fetal life, net "providers“ in adult Developing organs, tissues are fragile therefore most blood kept away and pressure low (40-50 mmHg MAP vs. 90-100 mmHg) to prevent tissue damage

Answer 141

1. Ductus venosus 2. Foramen ovale 3. Ductus arteriosus ‘shunt’ – a passage or anastomosis between two natural channels such as blood vessels

Answer 142

They help during physiological stress during birth. are vital during fetal development to ensure efficient blood circulation before birth. They help bypass certain organs that are not fully functional until after birth. Distribute towards essential organs and away from non-essential organs

Answer 143

The urachus is a fibrous remnant of the allantois. It was a canal that drains the urinary bladder of the fetus that joins and runs within the umbilical cord. The fibrous remnant lies in the space of Retzius, between the transverse fascia anteriorly and the peritoneum posteriorly

Answer 144

answered version

Answer 145

low resistance vessel in liver Links UV to caudal VC DV allows 50% blood to bypass liver DV preferentially streams blood to foramen ovale (Not present in the fetal horse!!) (Not a single shunt in the fetal pig!!)

Answer 146

labelled version

Answer 147

an effective bypass that saves blood coursing through the whole of liver vasculature (not needed in foetus). It connects the umbilical vein to the caudal vena cava.

Answer 148

Shunts oxygenated blood straight through RA to LA Pressure differece across foramen ovale keeps it open in foetus patency maintained (kept open) by high blood flow

Answer 149

Shunts blood in pulmonary artery straight to descending aorta Pressure differential between lungs and lower body streams flow back to placenta Allows equivalent ventricular function in foetus – helps develops ventricular musculature and vasculature

Answer 150

Umbilical vein delivers nutrients TO FETUS… Umbilical arteries delivers blood back TO PLACENTA Urachus fibrous remnant of allantois.

Answer 151

Connects Umbilical Vein with caudal VC. Allows blood to bypass hepatic circulation

Answer 152

Foramen Ovale streams blood from right to left atrium (rather than RV) Ductus Arteriosus streams blood from RV to descending aorta (rather than lungs)

Answer 153

Fetal lungs were collapsed, now they are air-filled (respiration) Fetal circulation becomes a CLOSED SYSTEM Fetus moves from parenteral to enteral nutrition Fetus now needs to regulate body temp Fetal kidneys now need to process waste.

Answer 154

Ductus Venosus (DV) Umbilical cord ligated (tied off), DV constricts, ligamentum venosum. Foramen Ovale (FO) Pulmonary resistance decreases, pressure differential causes offset septa to close and fuse. Blood flows to lungs. remnant is called the FOSSA OVALIS Ductus arteriosus (DA) pressure differential causes DA to close and fuse remnant called ligamentum arteriosum (6, right)

Answer 155

Pressure changes secondary to lung inflation (PaO2 increases) Changes in hormones (cortisol, catecholamines, prostaglandins) Vascular resistance changes Tissue layers pushed together fuse and fibrose, become ligaments

Answer 156

all shunts close. Placenta is separated.

Answer 157

functional closure in minutes due to improved pulmonary clearance, no umbilical blood supply anatomical closure within days

Answer 158

Functional closure is relatively quick i.e. hours Anatomic closure is relatively slow (weeks-years) with a small opening persisting in about 25% mammals. Failure to close results in atrial-septal defect ‘Hole in the heart’

Answer 159

Functional closure in mins to hours. Anatomic closure may take 2-7 days If closure does not occur, ventricular septal defect = patent ductus arteriosus. Relatively common condition Non-life threatening Reduces efficiency of heart Exertional incompetence

Answer 160

Internal umbilical arteries – round ligaments of the bladder. Internal umbilical vein – round ligament of the liver. 1. ductus venosus becomes ligamentum venosum. 2. foramen ovale becomes fossa ovalis 3. ductus arteriosus becomes ligamentum arteriosum

Answer 161

Increased oxygenation Haemoglobin alters from fetal to adult Blood pressure increases Enteral intake of nutrients

Answer 162

Endotherm is an organism that maintains its body at a metabolically favourable temperature, largely by the use of heat released by its internal bodily functions instead of relying on ambient heat. An ectotherm is a animal that is dependent on external sources of body heat. Cold-blooded.

Answer 163

A homeotherm is an animal that maintains its body temperature at a constant level, usually above that of the environment, by its metabolic activity. A poikilotherm is an animal that cannot regulate its body temperature except by behavioural means such as basking or brumation.

Answer 164

Yes its true all homeotherms are endotherms and all ectotherms are poikilotherms.

Answer 165

4 physical processes of heat exchange include conduction, convection, radiation and evaporation. Conduction – heat transfer through direct contact between two objects. E.g. a dog lying on a cold floor. Convection – heat transfer through the movement of air or liquid. E.g. horse exposed to strong winds during cold weather. Radiation – heat transfer in the form of electromagnetic waves. E.g. a dark coloured dog in a hot environment with no shade Evaporation – heat loss through the conversion of water from a liquid to a vapor. E.g. A dog panting excessively in a hot and humid environment.

Answer 166

Rate of heat storage = metabolic rate – (conduction + convection + radiation – evaporation)

Answer 167

The thermoregulatory centre is located in the hypothalamus, a small region at the base of the brain. Two types of temperature sensors, peripheral thermoreceptors (in skin and other tissues detect changes in the external environment) and central thermoregulators (monitor the core body temperature). Hypothalamus receives and integrates temperature information from both peripheral and central thermoreceptors. It compares this information to the body’s set point temperature. When the body is too hot, hypothalamus causes vasodilation and sweating to occur. When the body is too cold, hypothalamus cause vasoconstriction, shivering and thermogenesis to occur. Thermogenesis is increased metabolic activity to produce heat.

Answer 168

Shivering, vasoconstriction, insulation, thermogenesis, behavioural adjustments (seeking shelter, huddling with others, or increasing food intake to generate more body heat)

Answer 169

Sweating, panting, vasodilation, behavioural adjustments (seeking shade, reducing activity levels, increasing water intake), radiation

Answer 170

specific to the type of animal thing back to alevel biology and specific specially adapted species to extreme environments like artic foxes, fennec foxes, whales things like that.

Answer 171

Thermoneutral zone describes a range of temperatures of the immediate environment in which a standard healthy adult can maintain normal body temperature without needing to use energy above and below the normal basal metabolic rate. Lower critical temperature is the lowest ambient temp at which an endothermic animal can maintain its core body temperature without increasing metabolic heat production, Higher critical temp is the highest ambient temp at which an endothermic animal can maintain its core body temperature without expending additional energy for cooling. The lower and upper critical temperatures define the thermoneutral zone. Thermal comfort is the condition of mind that expresses subjective satisfaction with the thermal environment. Thermal set point refers to the target temp that an organisms body aims to maintain. Ideal core temp for physiological processes.

Answer 172

When a lamb is wet, the LCT falls more easily, making it harder for the lamb to maintain its body temp without expanding extra energy.

Answer 173

High-producing cows generate more metabolic heat, making them more vulnerable to cold stress. Maintenance cows normally have more fat reserves due to not having to deal with the energy demands of milk production. High producing cows can tolerate lower temperatures better due to their higher metabolic heat production.

Answer 174

Low Body Temperature: Normal body temperature for lambs is around 39°C-40°C (102°F). A temperature below 37°C (98.6°F) indicates hypothermia Behavioral Signs: Look for weak, lethargic lambs that are unable or unwilling to suckle. They may also have a hunched posture and hollow flanks. Physical Signs: Cold ears, mouth, and extremities are common indicators

Answer 175

Risk Factors: Weather Conditions: Cold, wet, and windy conditions increase the risk of hypothermia Birth Complications: Lambs that experience difficult births or are born prematurely are more susceptible. Inadequate Colostrum Intake: Lambs that do not receive enough colostrum within the first few hours of life are at higher risk

Answer 176

Immediate Actions: Dry the Lamb: Remove the lamb from the ewe and dry it off if it is wet Warm the Lamb: Place the lamb in a warming box or use a heat lamp to gradually raise its body temperature Provide Energy: Administer warm colostrum by stomach tube if the lamb is able to swallow. If the lamb is too weak to suckle, intraperitoneal dextrose may be necessary before warming

Answer 177

Monitoring and Aftercare: Regular Temperature Checks: Monitor the lamb's rectal temperature to ensure it is returning to normal Continued Feeding: Ensure the lamb receives adequate colostrum and continues to feed regularly to maintain energy levels. Shelter and Bedding: Keep the lamb in a warm, dry, and draft-free environment until it is strong enough to return to the ewe

Answer 178

Preventive Measures: Ewe Nutrition: Ensure ewes receive proper nutrition during the last six weeks of pregnancy to support fetal development and colostrum production Lambing Environment: Provide a clean, dry, and sheltered area for lambing to reduce exposure to cold and wet conditions Colostrum Management: Have frozen colostrum on hand and ensure lambs receive it within the first few hours of life

Answer 179

The last six weeks of pregnancy, is the time of most rapid lamb growth and is when the brown fat is laid down around the lamb’s heart and kidneys. This brown fat is the only energy source for the newborn animal and will keep the lamb alive and vigorous for about five hours after birth. In normal conditions, this is enough time to allow the lamb to dry off and start to suckle. Once suckling properly, the colostrum takes over as the main source of energy.

Answer 180

In managing hyperthermia – cooling methods include shade and ventilation, misting systems and cool water baths.

Answer 181

Bair hugger is a forced-air warming device, often needed in the medical setting to manage and maintain a patient’s body temp. In preventing hypothermia during surgical procedures, in critical care, recovery and managing specific conditions like shock and in neontral care.

Answer 182

Congenital Cardiac Defects (CCD) arise due to abnormalities in the normal embryologic development of the heart, typically occurring during the first 8 weeks of gestation, when the heart is forming and differentiating. USE failure of development CCD image for help

Answer 183

Animals with Congenital Cardiac Defects (CCD) resulting from developmental failures often present with a range of clinical signs that reflect impaired cardiac function, altered blood flow, and reduced oxygen delivery.

Answer 184

Congenital Cardiac Defects (CCD) can severely affect both oxygen delivery and cardiac function, depending on the type, severity, and direction of blood flow changes caused by the defect. effect lower cardiac output, caused by overload or obstruction, outcome is weakness, poor perfusion effect lower oxygenation, caused by Right to Left shunts or pulmonary issues, outcome is cyanosis (blueish decolouration), hypoxemia effect higher pulmonary flow, caused by left to right shunts, outcome is pulmonary oedema, respiratory signs effect myocardial strain, caused by chronic overload, outcome is heart failure, arrythmias

Answer 185

Aberrant vascular development refers to abnormal formation or remodeling of blood vessels during embryogenesis, and it can significantly disrupt circulatory function, oxygen delivery, and organ development. These abnormalities can involve arteries, veins, or capillaries, and may be isolated or associated with congenital heart defects (CCD). effects altered blood flow patterns, obstruction of vessels, ischemia and tissue hypoxia (insufficient blood flow and insufficient oxygen levels in tissues), congestive signs (improper drainage of blood), heart failure (compensation for abnormal vascular patterns)

Answer 186

The cardiac conduction system is made up of specialized structures that generate and transmit electrical impulses, ensuring the heart beats in a coordinated and rhythmic way. Its key structural components are: Sinoatrial (SA) Node Located in the right atrium near the superior vena cava. It’s the natural pacemaker of the heart — it initiates electrical impulses that set the heart rate. Atrioventricular (AV) Node Located at the junction between the atria and ventricles. It delays the impulse slightly, allowing the atria to contract fully before the ventricles are stimulated. Atrioventricular (AV) Bundle (Bundle of His) Originates from the AV node. It’s the only electrical connection between the atria and ventricles. Right and Left Bundle Branches These branches run along the interventricular septum. They carry impulses toward the apex of the heart. Purkinje Fibers Spread throughout the ventricular walls. They distribute the electrical impulse to the ventricular muscle, causing the ventricles to contract.

Answer 187

Functional Characteristics that Enable Conduction: Automaticity Cells (especially in the SA node) can spontaneously generate electrical impulses without external stimulation. Conductivity Cells can rapidly transmit electrical signals from one cell to another. Excitability Cells respond to an electrical stimulus by depolarizing and initiating an action potential (electrical signal). Rhythmicity Cells (especially in pacemaker areas) fire impulses in a regular, repeating pattern to maintain steady heartbeats. Synchronization Structures like the AV node and Purkinje fibers ensure that the atria contract first, followed by the ventricles in a coordinated way. Functional Characteristics that Block Conduction: Refractory Periods After an action potential, cells temporarily can't be re-excited. This prevents chaotic, overlapping signals and protects the heart from abnormal rhythms. AV Node Delay The AV node purposely slows down the impulse so the ventricles have time to fill with blood before contracting. Insulating Structures (Fibrous Skeleton of the Heart) There’s a fibrous connective tissue around the heart valves that blocks direct electrical spread from atria to ventricles — ensuring impulses only pass through the AV node. Diseases or Damage (Pathological Block) Conditions like fibrosis, ischemia, or infarction can create abnormal blocks (e.g., AV block), disrupting normal conduction.

Answer 188

Phase 4 – Resting Membrane Potential Potassium (K⁺) channels are open, and K⁺ leaks out of the cell. The inside of the cell stays negative compared to the outside (~–90 mV). The cell is ready for stimulation. Phase 0 – Rapid Depolarization When stimulated, voltage-gated sodium (Na⁺) channels open. Na⁺ rushes into the cell. The inside of the cell becomes positive quickly (depolarization). Phase 1 – Early Repolarization Na⁺ channels close (inactivate). Some K⁺ channels open, and K⁺ exits the cell slightly. A small, brief drop in membrane potential occurs. Phase 2 – Plateau Phase Calcium (Ca²⁺) channels open (L-type). Ca²⁺ enters the cell slowly while K⁺ continues to exit. This creates a balance — the membrane potential stays relatively steady. Important: This phase allows time for muscle contraction, so the heart can pump blood. Phase 3 – Final Repolarization Ca²⁺ channels close. More K⁺ exits the cell rapidly. The inside becomes negative again, returning to resting state.

Answer 189

Sympathetic Nervous System Effects Neurotransmitter: Norepinephrine (and also epinephrine from adrenal glands) Effects on Sinoatrial (SA) Node: Increases firing rate → Faster heart rate (positive chronotropy) Speeds up the depolarization of pacemaker cells. Effects on Atrioventricular (AV) Node: Increases conduction speed → Signals move through the AV node faster (positive dromotropy) Reduces the AV node delay, speeding up ventricular contraction. Parasympathetic Nervous System Effects Neurotransmitter: Acetylcholine Effects on Sinoatrial (SA) Node: Decreases firing rate → Slower heart rate (negative chronotropy) Slows the rate of spontaneous depolarization in pacemaker cells. Effects on Atrioventricular (AV) Node: Decreases conduction speed → Slower movement of impulses through the AV node (negative dromotropy) Prolongs the AV node delay, slowing ventricular contraction.

Answer 190

SNS effects - increases pacemaker depolarization - shortens the action potential duration in atrial and ventricular muscle cells so you have a faster repolarization - overall faster Heartbeat, stronger contractions, quicker readiness for next beat PNS effects - pacemaker cells depolarize more slowly so heart rate decreases - slightly prolongs the action potential duration (especially in the atria and AV node) - prevents rapid firing - overall result slower heartbeat, weaker excitability, longer rest before next impulse

Answer 191

LF - YELLOW LH = GREEN RF - RED RH - BLACK

Answer 192

average size of red blood cells

Answer 193

amount of haemoglobin in red blood cells

Answer 194

average amount of haemoglobin in a red blood cell

Answer 195

the electrical activity of the heart

Answer 196

P wave (represents the electrical depolarization of the atria in the heart), QRS complex (ventricular depolarization), T wave (repolarization of the ventricles)

Answer 197

Heart beat over a certain time, whether the heart is beating slower or faster than normal, whether there is a regular or irregular rhythm and can show where irregularities in the beat occur.

Answer 198

In cardiac ultrasound the valves are visible but electrical activity is not visible and the opposite is true for ECG. Therefore by using ECG it is possible to diagnose problems in electrical activity but not if there are problems with the valves and again the opposite for cardiac ultrasound. Ultrasound will also show the movement of blood through the heart.

Answer 199

Commonly in practice, 4 electrodes/cables are used to produce 6 leads, or views. Each lead is recording the heart's electrical activity from a different direction –The ECG trace shape is created when the electrical impulse moves towards or away from the electrode:

Answer 200

- electrical activity towards a lead causes an upward deflection - electrical activity away from a lead causes a downward deflection In practice we mostly concentrate on lead II – most useful for assessing arrythmias

Answer 201

P - atrial contraction QRS - contraction of the ventricles T - relaxation of the ventricles

Answer 202

The cause is unknown, the atrioventricular valves degenerate as the dog gets older. Dogs often have a murmur for a number of years - typically noted over the AV valve initially. Many develop signs of heart failure as they get older.

Answer 203

Angiogenesis: the sprouting of new capillaries from pre-existing vessels

Answer 204

Vasculogenesis: formation of blood vessels from endothelial progenitor cells form a primitive vascular network i.e. angioblasts issued from the mesoderm during embryogenesis.

Answer 205

they can occur at the same time While vasculogenesis and angiogenesis are different processes, they can occur simultaneously, particularly in embryonic development or in situations like tissue repair. In the early stages of development, vasculogenesis sets up the basic vascular network, and angiogenesis may then follow to refine and expand this network as the tissues grow and need more blood supply. In adults, angiogenesis is more common as it happens in response to the need for new blood vessels in specific tissues or to repair damage, whereas vasculogenesis is usually more limited.

Answer 206

they switch on angiogenesis. VEGFA, Hypoxia, Angiopoietins, PDGF, IGF, MMPs, In tegrins

Answer 207

these switch off angiogenesis examples include - angiostatin, throm bospondin. PEDF, endostatin, Soluble FLT1

Answer 208

Fetal and post-natal development Metabolically active tissue needs to be “close” to a capillary for gaseous exchange Limited in adults Principally in female reproduction i.e. uterine/ovarian changes and placental development Pathology Wound healing Skin / heart disease Tumour development

Answer 209

low levels of oxygen in your blood tissues. It is a strong inducer for the formation of new blood vessels.

Answer 210

Angiogenesis occurs in response to hypoxia Hypoxia inducible factor (HIF) is transcribed when low levels of oxygen is detected it causes new blood vessels to be formed.

Answer 211

1 - the systemic circulation 2- the pulmonary circulation

Answer 212

However a few organs are connected “in series” they obtain their blood “second hand” from the venous outflow of another organ. This is called portal system

Answer 213

A portal system permits to transport blood solutes without dilution in the general circulation.

Answer 214

Hepatic portal vein in all vertebrate: From the GI to the Liver. Filter newly absorbed compounds Renal portal vein in all vertebrate-not mammals (birds) From the hind limbs to kidney Resorb salt, water…

Answer 215

Collateral circulation refers to alternate or backup blood vessels in your body that can take over when another artery or vein becomes blocked or damaged. These then can link back to the original vessel by a anastomosis (bridge)

Answer 216

Delivery system: arteries and arterioles High pressure ~15% blood volume Exchange system: capillaries Intermediate pressure ~5% blood volume Return system: venules and veins Low pressure ~80% blood volume (nothing else but a reservoir of blood)

Answer 217

answered version

Answer 218

Smooth muscles, collagen, elastin

Answer 219

smooth muscles, collagen, elastin

Answer 220

collagen, elastin

Answer 221

elastin forms a network that allows vessels to recoil

Answer 222

all proportionally equivalent, except arteriole which is lower and capillary which is higher.

Answer 223

capillary, venule non existent, arteriole, vein, vena cava relatively low, artery slightly higher, aorta the highest

Answer 224

aorta to arteriole it increases. Capillary, venule not present. Vein to vena cava increases.

Answer 225

aorta and vena cava is the highest. Vein, artery, arteriole are all on par. venule is lower and capillary is non existent.

Answer 226

Blood pressure will change along the vascularity’s. Oscillations varies more in the arteries and then drops in the arterioles due to the lower levels of elastin and collagen. Then steeply goes down.

Answer 227

pulse pressure = systolic pressure - diastolic pressure

Answer 228

The arterioles are composed of smooth muscle cells. These cells can contract in diminishing the radius of arterioles A decrease in the radius results in corresponding increase in blood pressure As a result, contraction of arterioles regulates the blood pressure. They provide the resistance to blood flow. Arterioles with hypotension will be less steep in the drop.

Answer 229

they have no collagen or elastin. High pressure would tear apart capillaries. Arterioles are needed before capillaries if not the capillaries would be killed off.

Answer 230

- diffusion - o2, co2, glucose, hormones, electrolytes - lipid soluble molecules can pass through cell membrane easily (drugs/therapeutics) - water soluble molecules generally require transport mechanisms to enter/exit cells

Answer 231

Continuous - continuous lining of endothelial cells except for clefts between cells Found in: majority in the body Fenestrated - Fenestrations are not true holes, but rather windows where the cell membrane is compressed to permit greater fluid transmission Found in: glomerular capillaries in the kidney Discontinuous sinusoid - some wider intracellular gaps permit increased exchange with surrounding tissues Found in: liver, bone marrow, lymphoid tissues, some endocrine glands

Answer 232

- the venous return depends on the pressure difference between venules and RA (changes in RA pressure changes venous return) - smooth muscles contraction in the tunica media - inspiration/ lower diaphragm/ abdominal compression - existence of venous valves - skeletal muscles - gravitation (upper parts of the body)

Answer 233

Blood circulation is controlled by the brain in the CNS. Blood is diverted from digestion and excretion to the skeletal muscles for exercise.

Answer 234

stroke volume

Answer 235

cardiac output and blood pressure

Answer 236

The amount of blood pumped in 1 minute

Answer 237

The volume entering the lungs must equal the volume entering the systemic circulation. Otherwise: - increase in pressure in venous side - leading to oedema (pulmonary or peripheral), hence - Co is tightly regulated by a range of mechanisms

Answer 238

preload, afterload and contractility

Answer 239

stroke volume = end distolic volume - end systolic volume

Answer 240

Preload is what is coming back from the venous system.

Answer 241

Contractility is how hard the heart contracts determines the end diastolic volume.

Answer 242

Venous return is affected by central venous pressure. What ever comes in is ejected both arrows should be the same size. It is like an elastic band. More energy put in more gotten out.

Answer 243

Bleeding decreases the venous return. If low - ventricular filling is reduced, thus stroke volume reduced.

Answer 244

Exercise helps increase the venous return. If high, ventricular filling is increased, hence stroke volume increases

Answer 245

Generally, a linear relationship between preload and stroke volume Ventricular muscle stretching leads to a stronger contractile force The stronger the stretching the stronger the force is up to the limits.

Answer 246

increased preload - increased exposure of myosin to actin - increased cross-bridge formation - increased force of contraction

Answer 247

Excessive stretching causes a decrease in cross-bridge formation Laplace’s law In a large sphere, more wall tension is required to generate the same internal pressure as it does in a small sphere as governed by: pressure = tension/radius

Answer 248

Enlarged heart can become a mechanical disadvantage as the tension generated in the walls has to be greater to form the same pressure to make it empty. clinical implications: Dilated cardiomyopathy, a common cardiac disease in dogs

Answer 249

Filling time of the heart Low heart rates > longer period for ventricular filling Greater distension of the ventricle Venous return i.e. Pressure difference between venous system and atrium The skeletal muscle pump The respiratory pump Sympathetic nervous system activity Blood volume

Answer 250

contraction of skeletal muscle - vein compressed (closed) - blood forced to heart - increased pre-load

Answer 251

during inspiration, diaphragm moves caudally which increases abdominal pressure, thorax pressure reduced which leads to an increased abdominal return of blood which increases preload.

Answer 252

- venous system acts as a reservoir for blood contains 2/3 of your blood - sympathetic stimulation of venous system causes venous vasoconstriction this increases venous pressure that leads to increased preload

Answer 253

look at answered version

Answer 254

Increases noradrenaline that increases calcium conc increasing contractility leading to a greater stroke volume.

Answer 255

Empty more completely and thus there is reduced end systolic volume Handle a greater pre-load and thus creates a greater filling volume Deliver an increased stroke volume, even when increased HR reduces time for ventricular filling To do all this against, if afterload is increased (increased aortic pressure) This involves the activation of 1-adenoreceptors. Beta 1 adrenoreceptors are involved in heart contraction

Answer 256

Inotropes - positive inotropes. positive inotropes lead to phosphorylation of CA2+ channels, which results in faster calcium re-uptake, sensitisation of troponin C to calcium. Increased contractibility. Positive inotropes increase heart contraction (inotropy). Release of calcium leads to an increase in tension of the muscle fibres.

Answer 257

- decreased force of contraction - inhibition of noradrenaline release from SNS - also decreases heart rate This involves activation of M2 muscarinic receptors This is the counterbalance system. Acetylcholine receptors. Acetylcholine can decrease force of contraction, inhibition of noradrenaline releases from SNS and it can also decrease heart rate.

Answer 258

Creates the resistance against which ventricle pumps Increased stroke volume leads to increased CO and thus increased afterload Also influenced by pressure of blood in circulation Principally affected by vasomotor tone Primarily arteriolar tone

Answer 259

Normal - The ejection pressure greater than afterload hence blood is ejected out of heart Reduced afterload More blood can be :ejected Increased afterload: Reduced stroke volume Heart has to work harder to maintain CO. Increased afterload occurs with hypertension. This elevates blood pressure which increases the afterload meaning the heart has to work harder to maintain CO.

Answer 260

The normal heart pumps venous return each cycle (This is called intrinsic control) Extrinsic mechanisms can overcome limits of intrinsic control enabling Increased contractility at a given preload Afterload is limiting factor in stroke volume in diseased animals (e.g. high blood pressure)

Answer 261

Intrinsic activity from SA (sino-atrial) node Controlled by sympathetic and parasympathetic NS enabling Rapid response (increased or decreased) Tightly regulated to maintain blood pressure Heart rate linked to baroreceptor activity in carotid artery

Answer 262

If blood pressure is elevated (transient), then there is Activation of parasympathetic NS that Heart rate slows Reducing cardiac output BP returns to normal

Answer 263

Activation of sympathetic NS that Increases heart rate Increases vascular tone Increasing cardiac output Restores blood pressure

Answer 264

Blood pressure (MAP) = CO x total peripheral resistance (TPR)

Answer 265

TPR is in effect Arterial vascular resistance (tone) and is influenced by: Sympathetic nervous system (α and beta-adrenoceptors) in the vasculature Renin-Angiotensin Aldosterone System (RAAS) Local Endothelial-derived factors affect the degree of afterload

Answer 266

Blood flow = pressure difference/ resistance Resistance is proportional to length/ radius to the power of 4

Answer 267

The only way the body can try and counter this is by increasing the pressure difference meaning the heart has to work a lot harder.

Answer 268

Pulse pressure = PSystolic – PDiasystolic

Answer 269

Mean arterial pressure= (Systolic+2(diastolic))/3

Answer 270

Influenced by: 1- Arterial compliance (aorta) “ability to accommodate the increase in pulse pressure” This decreases with age 2- Stroke volume 3- Consistent high pulse pressure will “age” the heart quicker

Answer 271

Bigger pulse pressure difference means the heart is having to work harder.

Answer 272

increased preload results in increased cardiac output

Answer 273

Cardiac output is the volume of blood ejected from the heart per minute.

Answer 274

stroke volume and heart rate

Answer 275

EDV and stroke volume are directly related. As EDV increases, the heart fills with more blood during diastole. Leading to a greater volume of blood being ejected during systole, thereby increasing the stroke volume.

Answer 276

EDV is the amount of blood in the ventricles of the heart at the end of the diastole, just before the heart contracts.

Answer 277

Venous return – This is the amount of blood returning to the heart from the veins. More venous return means more blood fills the ventricles, increasing EDV. Ventricular compliance – This refers to how easily the ventricles stretch to accommodate incoming blood. A more compliant (flexible) ventricle allows greater filling, leading to a higher EDV.

Answer 278

The Frank-Starling mechanism is the heart’s way of adjusting its force of contraction based on how much blood fills the ventricles. It states that the more the heart fills with blood during diastole (higher end-diastolic volume, or EDV), the stronger the contraction during systole, leading to an increased stroke volume.

Answer 279

Contractility refers to the inherent strength of the heart's contraction, independent of muscle fiber stretch (Frank-Starling mechanism) and preload (end-diastolic volume). It is influenced by cellular and molecular factors that regulate how forcefully the heart muscle contracts.

Answer 280

Cardia output is generally more important than blood pressure for ensuring adequate delivery of oxygen and nutrients to peripheral tissues. It is more of a direct indicator of tissue perfusion, however maintaining an adequate blood pressure is still necessary to ensure proper circulation. Perfusion is the passage of fluid through the circulatory system or lymphatic system to an organ or a tissue.

Answer 281

During physical exercise, the contractility of the heart increases, meaning the heart pumps more forcefully. This leads to a greater stroke volume (SV) and cardiac output (CO), ensuring that oxygen-rich blood reaches active muscles.

Answer 282

Sympathetic Nervous System (SNS) Activation Exercise stimulates the sympathetic nervous system. Norepinephrine (from sympathetic nerves) and epinephrine (from adrenal glands) bind to β₁-adrenergic receptors on heart muscle cells. This increases intracellular calcium (Ca²⁺) levels, leading to stronger and faster heart contractions. Increased Calcium Availability More Ca²⁺ enters cardiac muscle cells via L-type calcium channels. Enhanced Ca²⁺ release from the sarcoplasmic reticulum amplifies contraction strength. More Ca²⁺ reuptake allows for faster relaxation, preparing the heart for the next beat. Decreased Vagal (Parasympathetic) Tone The parasympathetic nervous system (PNS) normally slows the heart via the vagus nerve. During exercise, vagal tone decreases, allowing increased heart rate and contractility.

Answer 283

Effects of Increased Contractility During Exercise: Higher stroke volume (SV) → More blood pumped per beat. Increased cardiac output (CO) → More oxygen and nutrients delivered to muscles. Improved ejection fraction (EF) → More efficient blood ejection from the ventricles. Conclusion: During exercise, the sympathetic nervous system, increased calcium handling, and reduced parasympathetic influence all enhance heart contractility, ensuring sufficient blood supply to meet the body’s increased oxygen demands

Answer 284

A major haemorrhage leads to a significant loss of blood volume, triggering compensatory mechanisms to maintain blood pressure, tissue perfusion, and oxygen delivery. Increased heart rate to compensate for reduced SV Venous return decreases initially and then recovers Total peripheral resistance increases (amount of force exerted on circulating blood by the vasculature of the body) Tissue fluid volume initially decreases then recovers – reduced blood movement causes fluid movement from interstitial spaces into the bloodstream Urine output decreases the body conserves fluid to maintain blood volume Regulation: The baroreceptor reflex (in aortic arch & carotid sinus) detects low BP and activates the sympathetic nervous system (SNS). This increases heart rate (HR) (tachycardia) via β₁-adrenergic receptors to compensate for reduced SV. Regulation: Vasoconstriction of veins (via SNS activation) increases venous return by mobilizing blood from the venous reservoir. Skeletal muscle pump and respiratory pump further aid venous return. Regulation: SNS activation causes vasoconstriction of arterioles, increasing total peripheral resistance (TPR). Angiotensin II (RAAS system) also promotes vasoconstriction Regulation: Capillary hydrostatic pressure drops, promoting fluid reabsorption from interstitial spaces into capillaries (plasma volume expansion). Increased oncotic pressure due to retained plasma proteins further pulls fluid into the circulation. Regulation: Renin-Angiotensin-Aldosterone System (RAAS) Low BP triggers renin release → angiotensin II formation → aldosterone secretion, which increases sodium & water retention. Antidiuretic Hormone (ADH) Hypovolemia stimulates ADH release from the posterior pituitary, increasing water reabsorption in the kidneys. Sympathetic vasoconstriction of renal arteries reduces glomerular filtration rate (GFR), further lowering urine output. Blood flow is prioritized to vital organs (heart, brain) at the expense of non-essential tissues (skin, GI tract). Look at major haemorrhage 1 and 2

Answer 285

In heart failure, cardiac output is reduced because the heart cannot pump blood effectively to meet the body’s demand. Because SV is reduced due to weak or stiff ventricles Heart fills with more blood but struggles to eject it effectively Compensatory mechanism are initially helpful but then turn to be harmful later on, such as the SNS activation (increases HR but leads eventually to heart exhaustion). RAAS causes vasoconstriction and fluid retention, after increasing afterload and worsening heart function. Ventricular hypertrophy and remodelling the heart adapts but becomes stiff and inefficient.

Answer 286

answered version

Answer 287

Neutrophils 6-12 hours Platelets 6-8 days RBC's 110-120 days

Answer 288

haematapoiesis

Answer 289

answered version

Answer 290

development of red blood cells Key points Proliferative pool (maturational division) Maturation pool Marrow transit time: 3-5 days EPO produced in the kidneys in response to tissue hypoxia. EPO stimulates the development of red blood cells. No reticulocytes in horses

Answer 291

how neutrophils develop. Key points: Proliferative pool Maturation pool Marrow transit time: ~ 1 week (can be less in inflammation)

Answer 292

how lymphocytes develop. Key points B lymphocytes  produced in the Bone marrow, Peyer’s patches (dogs, pigs and ruminants) and Bursa of Fabricius (birds) T lymphocytes  mature in the Thymus NK  mature in the bone marrow Once mature they colonise the lymphoid organs (e.g., lymph nodes, spleen, MALT)

Answer 293

thrombopoiesis Key points Endomitosis  nuclear duplication without cell division Cell volume increases with each nuclear duplication Marrow transit time: 7-10 days TPO produced mainly in the liver These cells get bigger as they develop

Answer 294

Erythrocytes (red blood cells) Platelets (thrombocytes) Leucocytes (WBC’s) Granulocytes (contain large numbers of cytoplasmic granules) Neutrophils Eosinophils Basophils Mononuclear Monocytes Lymphocytes T-cells (50-75%), B-cells (10-40%), NK cells (5-10%) Named on their staining properties

Answer 295

Leucocytosis – too many Neutrophilia (neutrophilic leucocytosis) Eosinophilia Basophilia Lymphocytosis Monocytosis Leucopenia – too little Neutropenia Eosinopenia Lymphopenia Monocytopenia

Answer 296

– a mixture of 2 stains that give a third colour (purple). like diff quick, with eosin and azure Used for the identification of leucocytes

Answer 297

Neutrophils, eosinophils and basophils. Neutrophils: lobed nucleus, often connected by thin strands of chromatin, sparse granules Eosinophils, lobed nucleus, dense orange granules, blue cytoplasm Basophils: lobed but not so well defined, dense blue granules with cytoplasm, rare in bloods of mammals Look at granulocytes image

Answer 298

10 – 12 microns. (slightly larger than a red blood cell) Circulate in the blood for minutes up to 6-8 hrs Survive in tissues 1 – 2 days 5 times more neutrophils in BM than blood Actively motile cells - ‘microphages’ (vs macrophages) Neutrophils & macrophages come from a single bipotential stem cell. Their development is influenced by; Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) Granulocyte-CSF IL-3 Don’t circulate or survive in tissue for very long. Bone marrow is always having to produce them.

Answer 299

Neutrophil activities: Chemotaxis Phagocytosis & killing oxygen-dependent oxygen-independent

Answer 300

Neutrophils have selectin receptors that interact with selectins on endothelial cells. IL-1 and TNF induce endothelial cells to express InterCellular Adhesion Molecule (ICAM)-1 and Vascular Cell Adhesion Molecule (VCAM)-1. The interaction between selectins and their receptors slows the cells’ passage. Eventually cells can escape the blood vessel – gaining access to the site of inflammation In most abscesses dying neutrophils make up the majority of pus.

Answer 301

Level in blood is balance of how many produced by bone marrow and how many the tissues are using.

Answer 302

heterophils. They do the same job but the cytoplasm of them isn’t neutral and something else is different. Functionally equivalent, but granules stain red

Answer 303

Myeloblast Promyelocyte Myelocyte Metamyelocyte Band neutrophil Segmented neutrophil

Answer 304

Often occurs during infection – acute phase Circulating neutrophil numbers increase Begin to see immature neutrophils or ‘band forms’ within the blood – leaving the BM early

Answer 305

Strongly associated with allergy, parasites & fibrosis Rarely found in healthy blood Specific granules contain: Major basic protein Eosinophil cationic protein Eosinophil peroxidase Eosinophil-derived neurotoxin Enzymes histaminase and collagenase Look at eosinophil species variation image

Answer 306

Can be weakly phagocytic Surface IgE receptors Specific granules heparin histamine leukotrienes Lysosomes Associated with parasitic infection and allergy Extremely rare in the blood Recruited into tissue

Answer 307

0-300 per microlitres in blood Basopenia is not cause for concern sign of pathology/disease

Answer 308

Have IgE receptors on their surface and ‘triggered’ when antigens bind surface IgE Granule contents released Particularly involved in the response to allergy and parasitic infections –’worms’ Found in connective tissue NOT blood Rounded nuclei Granular cytoplasm Granules release: Histamine Heparin Proteases (Chymase and/or Tryptase) Leukotrienes ‘slow reacting substance of anaphylaxis’ Eosinophil chemotactic factor Neutrophil chemotactic factor Interleukins, TNF- ; Prostaglandin D

Answer 309

Arise from same precursors as neutrophils Monocytes present within blood but not tissue Reptiles have additional mononuclear cell - “azurophil” Exit of blood into tissue or lymph node gives rise to macrophages and dendritic cells

Answer 310

Macrophages Phagocytosis pathogens, foreign bodies, antigen Communicate with T-cells Dendritic Cells Primarily communicate with T-cells

Answer 311

bursa of fabricius

Answer 312

B cells develop in the: bone marrow in some species intestine in some species e.g. sheep

Answer 313

T lymphocytes Develop in bone marrow Always enter thymus for “education”

Answer 314

no, also struggle to occasionally identify NK cells because of granules in cytoplasm

Answer 315

Cytopathologists review the proportion of cells, whether we see all the development stages and the type and number of cells.

Answer 316

Neoplasia of the WBC, instead of seeing a mixture of neutrophils, lymphocytes and monocytes, we get one clonal population of cells developing. They become very similar and they're normally bigger cells. Very similar cells to each other, they might look like a monocyte or lymphocyte but we would call that a leukaemia.

Answer 317

band neutrophils they lack segmentation of the nucleus

Answer 318

size 12-15 micrometeres. lobulated nucles 2-4 lobes pale pink or light blue cytoplasm

Answer 319

both are 12-20 micrometres in diameter both have a lobulated nucleus basophils the granules are blue eosinophils the granules are orange-red

Answer 320

size 15-20 micrometer irregular shaped nucleus, lacy reticulated chromatin - blue-grey cytoplasm

Answer 321

size 9-12 micrometre in diameter nucleus round with condensed chromatin pale blue cytoplasm

Answer 322

92% water 7% protein 1% other

Answer 323

Structure: typical lipid bilayer membrane of globular proteins Biconcave disc shape Increases surface area (20-30%) Elasticity/deformability  Passage of capillary diameters as small as 3-4

Answer 324

Failure of Na+ ion movement across erythrocyte cell membranes

Answer 325

Dog Uniform size Central pallor (concave) Cat Smaller erythrocytes Anisocytosis (variation in size) Scarce central pallor (less concave)

Answer 326

horse - rouleaux formation (clustering of RBCs in standing blood) Ruminant (spiky appearance), variation in size camelid - elipsoid

Answer 327

Nucleated Larger Early stages are rounded and may be binucleate Occasional cells lose their nucleus and are termed erythroplastids.

Answer 328

inflammation except horses

Answer 329

Erythrocytes are metabolically active. Energy is required to maintain electrolyte gradients across the plasma membrane and of haemoglobin molecules. There are no organelles No mitochondria - Energy is derived by anaerobic metabolism of glucose avoiding consumption of any oxygen they are carrying No nucleus in mammalian erythrocytes – division stem cells Increased space for haemoglobin allows biconcave shape

Answer 330

98.5% - 1.5% dissolved in blood

Answer 331

10% 70-85% bicarbonate 5-15% dissolved in blood

Answer 332

Most bicarbonate is produced in erythrocytes after carbon dioxide diffuses into the capillaries, and subsequently into red blood cells. Carbonic anhydrase (CA) causes carbon dioxide and water to form carbonic acid (H2CO3), which dissociates into two ions: bicarbonate (HCO3–) and hydrogen (H+).

Answer 333

represents 95% of erythrocyte protein (1) Globin two pairs of polypeptides: x2 alpha and x2 beta (97% adult hg) delta (3% adult Hg) gamma (foetal Hg) epsilon (embryonic Hg/yolk sac) (2) central haem group containing an iron atom that can bind a molecule of O2 Each can bind one Look at haemoglobin image

Answer 334

In regions of high oxygen concentration (eg in the lung):  globin releases CO2 and iron binds to O2 (oxyhaemoglobin) In areas of low oxygen concentrations:  O2 is released and CO2 bound (carbaminohaemoglobin)

Answer 335

In hypoxic tissues (lack of O2) a carbohydrate (2,3-diphosphoglyceride) is released  that facilitates release of O2 from erythrocytes. Haemoglobin also binds nitric oxide – a neurotransmitter that causes dilation of blood vessels  permitting maximal tissue perfusion for supply of oxygen/removal of waste products.

Answer 336

process occurs in red bone marrow + spleen red bone marrow found at ends of long bones and in flat bones

Answer 337

yolk, sac, liver - shift to bone marrow in later foetal stage primarily in marrow of membranous bones nucleated immature RBCs

Answer 338

Sinusoidal capillaries with larger intercellular gaps to allow passage of cells Inactive marrow is replaced by fat (yellow marrow) but can regain activity by extension from active tissue and from circulating stem cells.

Answer 339

Nucleus becomes progressively smaller Cell size becomes progressively smaller Haemoglobin levels gradually increase

Answer 340

protein iron copper folic acid vitamins (B2, B6, B12)

Answer 341

~70% as haemoglobin; ~30% bound to ferritin in macrophages in liver, spleen and bone marrow. Some (<0.1%) bound to protein (transferrin) in plasma.

Answer 342

1. Physiological anaemia in newborns Example: piglets Markedly reduced RBC numbers in 1st 2-3 days of life Iron store used up within 1-2 days Sow milk contains very little iron caused by Rapid growth due to breeding 2. Blood loss Internal or external parasites 3. Haemorrhage Internal or external

Answer 343

Hormone that controls rate of erythrocyte production

Answer 344

Source early embryonic/foetal/early neonatal life  expressed in yolk sac, liver and kidney (also spleen and bone marrow). adult life  produced in the kidney (renal interstitium

Answer 345

Low kidney oxygen Circulatory failure, anaemia; (normal O2 but low delivery) Hypoxia (low O2) EPO transported by blood to bone marrow EPO binds to receptors on CFU-E (Erythroid cells precursors ) causing increased production of erythrocytes in the bone marrow EPO also accelerates release of reticulocytes  blood It is not the number of erythrocytes that regulates the secretion of EPO but the tissue needs for oxygen!

Answer 346

As they age, normal RBCs: lose sialic acid residues from their surface  exposing galactose moieties that induce their phagocytosis become more fragile. may become swollen due to failure of normal membrane function.

Answer 347

Average erythrocyte life spans: 70 days - cat 120 days - dog, human 145 - horse 160 days - cattle The normal lifespan of compatible transfused erythrocytes is much shorter!! In dogs it is approximately 21 days.

Answer 348

- damaged RBCs phagocytized by macrophage - recycling of haemoglobin

Answer 349

Free iron is toxic to cells as it acts as a catalyst in the formation of free radicals from reactive oxygen species. Iron molecules released from haem - conveyed to bone marrow by transferrin - stored as insoluble iron in macrophages and hepatocytes as ferritin

Answer 350

Serum protein involved in iron transport (synthesized in liver) Transferrin-iron complexes bind to cell-surface receptors causing internalisation of transferrin-iron-receptor complex. Low intracellular pH within endosomes cause dissociation of iron from transferrin-receptor-complex The transferrin-receptor complex dissociate at the cell surface recycling the system.

Answer 351

Ferritin - the primary intracellular iron-storage protein keeping iron in a soluble and non-toxic form - releases iron in a controlled fashion. It is a buffer against iron deficiency and iron overload. Haemosiderin - Intracellular complex of ferritin, denatured ferritin and other material. - Iron within deposits of hemosiderin is very poorly available to supply iron when needed. Large deposits may lead to organ damage.

Answer 352

1. Mycoplasma haemofelis (Haemobartonella felis) 2. Neonatal erythrolysis Foals, kittens Blood group incompatibility Maternal antibodies taken up through colostrum lyse RBCs

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