4 - STRUCTURE AND FUNCTIONS OF SYSTEMS

Question 1

what are the (4) main types of tissue?

Answer 1

epithelial (skin or internal organ covering)

connective (bone, cartilage, blood)

nervous

muscle

Question 2

differentiate between negative and positive feedback

Answer 2

negative feedback: bringing conditions back to their normal or homeostatic function

positive feedback: an action that intensifies a condition so that it is driven further beyond its normal limits (e.g., labor contraction, lactation, or sexual orgasm)

Question 3

how many lobes are in your right and left lung?

Answer 3

right lung: 3 lobes

left lung: 2 lobes

Question 4

what is the membrane surrounding the lungs called? what are it’s 2 layers called?

Answer 4

pluerae, a membranous cover

inner layer: visceral pleura
- lines the lungs

outer layer: parietal pleura
- lines the chest cavity aka thoracic cavity

in between is the interpleural space

Question 5

what is the diaphragm? what role does the diaphragm play?

Answer 5

a muscle that’s the lower border of the thoracic cavity. separates the thoracic cavity from the abdominal cavity

when you inhale, the diaphragm flats, allowing your chest cavity/lungs to expand

when you exhale, the diaphragm relaxes and pushes back upward which causes your chest and lungs to shrink in size, forcing air outward

Question 6

what type of cell lines the respiratory tract? what do they do? where are these cells found?

Answer 6

respiratory epithelium

they produce mucus to moisten and protect our airways

the cells also have cilia which sweep away trapped pathogens and particles

found everywhere in the respiratory tract except the pharynx and larynx

Question 7

list the structures of the respiratory tract in order

Answer 7

mouth/nose

pharynx

larynx

trachea

bronchi

bronchiole

alveoli

Question 8

in the nose/mouth, what cell secretes mucus?

Answer 8

goblet cells (part of the respiratory epithelium)

Question 9

what role does the pharynx play?

Answer 9

serves as the passageway for air and food (to the respiratory system and the digestive system)

Question 10

what happens if a piece of food gets stuck in your windpipe?

Answer 10

the larynx will trigger the cough reflex to clear your airways

Question 11

describe the structure of the trachea

Answer 11

a tube lined with c-shaped cartilage rings

Question 12

what’s the epiglottis?

Answer 12

a structure covering the trachea, preventing solids/liquids from accidentally entering. when we breathe air, the epiglottis remains open so air can pass thru

Question 13

what are alveoli? describe them

Answer 13

where gas exchange occurs between the respiratory and circulatory system

small, grape-like clusters

have a thin layer of cells, surrounded by capillaries. this layer serves as the interface between the respiratory system and the circulatory system

coated with surfactant, a liquid covering that reduces the surface tension, preventing H2O from collapsing the alveoli

Question 14

what role does surfactant play in the respiratory system?

Answer 14

is a coating the covers alveoli, preventing it from collapsing as we inhale and exhale

Question 15

what are the (2) major functions of the respiratory system?

Answer 15

internal respiration

external respiration

(both work together to get oxygen from the outside environment into our body’s cells and CO2 out our blood and exhaled)

Question 16

differentiate between internal and external respiration

Answer 16

external respiration
- entry of air into lungs
- gas exchange between alveoli and blood (CO2 from blood to lungs to be exhaled; O2 from lungs to blood) – supplies blood with oxygen

internal respiration
- gas exchange between blood and cells (CO2 from cells to blood to be taken away to lungs; O2 from blood to cells) – supplies cells with oxygen
- intracellular respiration processes

Question 17

how does gas exchange between the alveoli and the capillaries occur (in the respiratory system)

Answer 17

via simple diffusion (no transport proteins needed!!): gases like oxygen and carbon dioxide can simply diffuse across the thin alveoli membrane

Question 18

how does CO2 move in the bloodstream? (how’s it transported?)

Answer 18

considered bulk flow!!: volumes of fluid move from an area of higher pressure in a capillary bed to an area of lower pressure in the tissues via filtration

primarily transported in the plasma, the liquid portion of blood in the form of bicarbonate (HCO3-)

most CO2 in the blood gets combined with water to form carbonic acid which then dissolved into bicarbonate and H+ ions. this reaction is catalyzed by enzyme, carbonic anhydrase. it occurs in red blood cells

can also be transported as it is (CO2). it can mix directly with the plasma as a gas or can bind with hemoglobin inside of the RBCs, forming carbaminohemoglobin

Question 19

how does oxygen move in the bloodstream? (how’s it transported?)

Answer 19

primarily transported in the blood via hemoglobin

this is considered bulk flow: volumes of fluid move from an area of higher pressure in a capillary bed to an area of lower pressure in the tissues via filtration.

Question 20

how do gases in the blood get to the cells of our body?

Answer 20

oxygen will be unloaded by the hemoglobin and diffuse out of the red blood cells across the thin walls of our blood vessels thru any interstitial fluid, finally entering the cell by diffusing across their membrane

CO2 follows the opposite path. it diffuses out of the cell, across the membrane, thru the interstitial fluids, and across the blood vessel walls where they can be transported by red blood cells as bicarbonate

Question 21

what part of the brain controls respiration? what does it do specifically and how?

Answer 21

medulla oblongata

makes sure you’re always breathing, whether it’s conscious or unconscious

will also adjust breathing rate depending on oxygen needs of the body. this is done thru chemoreceptors which monitor levels of certain chemicals in the blood. the medulla specifically looks for H+ ions in the bloodstream. this is because when CO2 is transported in the blood, the process produced H+ ions. so when there’s lots of CO2, there will be lots of H+ ions. the medulla will signal the diaphragm contract so oxygen can be brought in and then CO2 exhaled.

some chemoreceptors also looks at concentrations of oxygen and CO2

an increase in H+ or CO2 will cause an increase in breathing rate. High blood oxygen partial pressure would cause a decrease in breathing rate.

Question 22

how are fish able to survive and get oxygen without being exposed directly to air?

Answer 22

gills are highly folded surfaces that provide a large surface area across which gas exchange can occur

to get oxygen from the water, fish use something called countercurrent exchange. as a fish swims thru water, water flows over the gills in the opposite direction of the blood that is flowing thru the fish. as the water and blood flow past one another, the oxygen that is dissolved in the water, diffuses into the bloodstream, replenishing the oxygen levels in the fish’s blood

this process occurs many times due to the large surface area which is how fish are able to survive from the oxygen gained from the countercurrent exchange

countercurrent exchange maximizes diffusion of oxygen into the blood and carbon dioxide into water

Question 23

why do fish die when they’re taken out of water?

Answer 23

water helps keep their gills separated, maintaining the large surface area

when removed from the water, their gills collapse onto one another, reducing the surface area. leads to death due to insufficient oxygen intake

** FISH DO NOT HAVE LUNGS!!

Question 24

describe hemoglobin

Answer 24

a protein that functions to transport oxygen in our bloodstream

has 4 polypeptide subunits. each of these subunits contain an Iron (Fe) atom which is critical to the function as Iron is what binds to the oxygen

Question 25

describe cooperativity in hemoglobins

Answer 25

in cooperativity, a molecule has multiple binding sites. when oxygen binds to one site, it increases the affinity for the next oxygen to bind. so, each oxygen that binds makes it easier for the next one to bind note that hemoglobin can bind up to 4 oxygens (1 for each iron atom) --- the reverse is true as well! when you remove an oxygen from hemoglobin, it becomes easier for the next oxygen to come off

Question 26

what is myoglobin?

Answer 26

used to transport oxygen to and from the cell in muscles equivalent of hemoglobin has a different binding affinity from hemoglobin

Question 27

describe the structure of hemoglobin

Answer 27

has 4 heme groups: each with an iron atom in the centre surrounded by a porphyrin ring. the iron is able to form up to 6 bonds, one of which is to the oxygen note that heme is a prosthetic group (a non protein, iron, attached to a protein)

Question 28

what does it mean when the oxygen-hemoglobin association curve has been shifted to the right?

Answer 28

leads to reduced affinity between oxygen and the hemoglobin. hemoglobin will release oxygen more easily -- due to increased oxygen demands, the hemoglobin will be less stingy! so, a left shift means increased affinity. hemoglobin will hold onto oxygen more tightly. this is when cells have less oxygen need

Question 29

what (5) factors causes the oxygen-hemoglobin association curve to shift right? describe these factors

Answer 29

"CADET - face right", an increase in the following will cause the curve to shift right CO2: an increase in CO2 = an increase in cellular respiration = oxygen being used up and supply needs to be replenished Acid: increased CO2 levels = more acid = hemoglobin is more likely to release oxygen due to conformational change induced by increased acidity (acidic = low pH). this conformational change will preferentially bind to CO2 2,3 DPG: a metabolite that gets consumed whenever oxygen is present. but if oxygen isn't present, 2,3 DPG builds up so it's presence indicates lack of oxygen in tissue Exercise: it consumes oxygen and produces CO2 during its process Temperature: high temp = high metabolic rate = consuming more oxygen and cells will demand more of it than usual

Question 30

define thermoregulation

Answer 30

control of exchange of heat with the environment

Question 31

differentiate between ectotherms and endotherms

Answer 31

ectotherms (COLD-BLOODED) - obtain body heat from the environment - include invertebrates, amphibians, reptiles, and fish endotherms (WARM-BLOODED) - generate their own body heat and have a much higher basal metabolic rate (BMR) than ectotherms

Question 32

what are cnidaria?

Answer 32

includes soft-bodied stinging animals such as corals, sea anemones, and jellyfish

Question 33

how does respiration work in cnidaria?

Answer 33

direct with the environment!! have large surface areas and every cell is either exposed to the environment or close to it → simple diffusion of gases directly with outside environment (flatworms and some small animals also exhibit this type of respiration)

Question 34

what are annelids?

Answer 34

include earthworms, polychaete worms, and leeches members of the group are to some extent segmented, in other words, made up of segments that are formed by subdivisions that partially transect the body cavity

Question 35

how does respiration work in annelids?

Answer 35

mucus secreted by earthworms provides a moist surface for gaseous exchange via diffusion the circulatory system brings oxygen to cells, and waste products back to the skin for excretion

Question 36

what are arthropods?

Answer 36

includes such familiar forms as lobsters, crabs, spiders, mites, insects, centipedes, and millipedes. distinguishing feature of arthropods is the presence of a jointed skeletal covering composed of chitin (a complex sugar) bound to protein

Question 37

how does respiration work in arthropods?

Answer 37

series of chitin-lined respiratory tubules called trachea that open to the surface via openings called spiracles, through which oxygen enters and carbon dioxide exits oxygen carriers such as hemoglobin are not needed due to the direct distribution and removal of respiratory gases between the air and body cells the moistened tracheal endings ease the rate of diffusion DIFFERENT FOR SPIDERS: they have book lungs that are stacks of flattened membranes enclosed in internal chambers

Question 38

describe the structure of lungs

Answer 38

these are invaginated structures made of two sub-portions: the left lung and right lung the left lung is smaller and consists of 2 lobes, while the right lung is made of 3 lobes left lung is smaller to accommodate the heart, which is also on the left side of the chest lungs have a membranous cover known as the pleurae, which have two pleura layers: the visceral and parietal pleura. the space in between these two layers is the intrapleural space

Question 39

describe the pressure in the intrapleural space (space between the two membranes of the lung) and lungs as we inhale

Answer 39

has negative (lower) pressure relative to the atmosphere. if stabbed, air rushes in and causes the lung to collapse the pressure of this intrapleural space decreases as we inhale: as the diaphragm contracts, the lung cavity opens up, and this increase in volume equates to a decrease in pressure similarly, the pressure inside of the lungs also changes. as we inhale, the volume of the lungs as expands as the diaphragm drops. by doing so, we create a negative pressure relative to the atmosphere, causing air to rush in considered bulk flow!!: the lungs increase in volume and decrease in pressure, leading to a bulk flow of air into lungs

Question 40

describe the haldane effect?

Answer 40

it describes how the deoxygenation of blood increases its ability to carry CO2 when hemoglobin is saturated with oxygen, its capability to hold CO2 is reduced. essentially, we pick up CO2 in the tissues where it’s generated, and get rid of it at the lungs and exchange it for oxygen. hemoglobin without oxygen acts as a blood buffer by accepting H+ → this reduced hemoglobin has a higher capacity to form carbaminohemoglobin, rather than the oxygen carrying kind, explaining how the Haldane Effect occurs. in summary, the Haldane Effect relates how [O2] is affecting hemoglobin’s affinity for CO2 and H+

Question 41

describe the bohr effect

Answer 41

when tissues are high in CO2, and therefore high in H+, tissues are not getting a lot of oxygen, and we want to oxygenate them as a result, the hemoglobin once near the tissues is exposed to the higher CO2 and H+ levels, and changes its structure to the reduced form. this reduced form now releases its O2 to the deoxygenated tissues, and preferentially binds to CO2. at the lungs, the CO2 wants out and is released. the H+ concentration is also lower here due to bicarbonate being converted back into CO2 for release. at this point, hemoglobin will change back to its non-reduced state that preferentially binds to oxygen, which holds it more tightly under these conditions. the Bohr Effect, therefore, relates to how CO2 and H+ affect hemoglobin’s affinity for O2. ---- hemoglobin binding affinity decreases under conditions of low pH (high CO2/high H+) which leads to oxygen loads released by hemoglobin since both oxygen and H+ compete for hemoglobin binding sites

Question 42

what is emphysema?

Answer 42

a disease marked by destruction of the alveoli

Question 43

what effects does smoking have on the respiratory system?

Answer 43

smoking can damage the cilia of respiratory cells and allow toxins to remain in the lungs mucus produced by goblet cells increases, and lungs have a decreased means of moving mucous out, leading to a persistent yet unproductive cough can lead to bronchitis, emphysema, and lung cancer

Question 44

differentiate between respiratory acidosis and alkalosis

Answer 44

Respiratory Acidosis - results from inadequate ventilation; we don’t clear enough CO2 and it builds up, so more H+ is formed, lowering the pH Respiratory Alkalosis - results from breathing too rapidly (hyperventilation); we are losing CO2 too quickly, so H+ and HCO3- start combining to form more CO2, and the pH begins rising

Question 45

differentiate between metabolic and respiratory acidosis/alkalosis

Answer 45

important to understand that metabolic acidosis and alkalosis are not due to breathing issues - you may alter breathing to compensate, but the cause is not breathing related.

Question 46

differentiate between the fetal and adult oxygen-hemoglobin dissociation curve

Answer 46

fetal hemoglobin curve is shifted left of the adult hemoglobin curve because the structure has a higher binding affinity in order to grab O2 from maternal blood

Question 47

differentiate between the oxygen dissociation curve of myoglobin and hemoglobin

Answer 47

myoglobin of muscle has a hyperbolic curve since the structure doesn’t participate in allosteric cooperative binding due to the single subunit shape myoglobin also saturates quickly and releases in situations of very low oxygen “emergency situations”

Question 48

what has a greater affinity for hemoglobin than oxygen?

Answer 48

carbon monoxide (CO) has a 200x greater affinity for hemoglobin than oxygen does [forms carboxyhemoglobin] and requires administration of pure oxygen to displace it once bound

Question 49

differentiate between respiration in mammals and birds (avian)

Answer 49

due to the unique anatomy of birds, respiration is both continuous and unidirectional air sacs allow birds to exchange gas during both inhalation and exhalation — oxygen rich incoming air is first stored in air sacs before entering lungs for exhalation, so it is not mixed with the deoxygenated outgoing air ---- In mammalian respiration there is tidal breathing — we breathe in and out through the same tubing, inhibiting gas exchange during exhalation. Deoxygenated air is mixed with some fresh air during inhalation, thus some of it is re-inhaled. Much less efficient than birds.

Question 50

what is tidal volume? (Vᴛ)

Answer 50

the volume of air that is normally inhaled or exhaled in one quiet breath

Question 51

what is inspiratory reserve volume (IRV)?

Answer 51

the maximum volume of air that can be inhaled after a normal tidal volume inhalation

Question 52

what is expiratory reserve volume (ERV)?

Answer 52

the maximum volume of air that can be exhaled after a normal tidal volume exhalation

Question 53

what is residual volume (RV)?

Answer 53

the amount of air remaining in the lungs after maximum exhalation air that cannot be exhaled

Question 54

what is vital capacity (VC)?

Answer 54

the maximum volume of air that can be exhaled after a maximum inspiration expressed as IRV + VT + ERV

Question 55

what is inspiratory capacity (IC)?

Answer 55

the volume of air that can be inhaled after a normal exhalation expressed as VT + IRV

Question 56

what is functional residual capacity (FRC)?

Answer 56

the volume of air remaining in the lungs after normal exhalation expressed as ERV + RV

Question 57

what is total lung capacity (TLC)?

Answer 57

the maximum amount of air that the lungs can accommodate expressed as IC + FRC

Question 58

Give the sequence that correctly describes the order of valves that blood passes through as it flows through the heart?

Answer 58

Tricuspid valve → Pulmonary valve → Mitral valve → Aortic valve

Question 59

what is pericardium? describe it

Answer 59

a double layered sac that envelopes the heart the outer layer: fibrous pericardium - protects the heart and holds it in place the inner layer: serous pericardium - consists of 2 layers with space in between: parietal, pericardial cavity, visceral - space (pericardial cavity) is filled with fluid that lubricates the heart as it pumps, preventing friction between the layers

Question 60

what are the (4) chambers of the heart? where are they in relation to each other?

Answer 60

right atrium / left atrium right ventricle / left ventricle atriums on top ventricles below

Question 61

what separates the 4 chambers of the heart?

Answer 61

upper and lower chambers are separated by valves the right and left sides are separated by the septum, a muscular wall

Question 62

which chambers carry oxygenated blood and which carry deoxygenated blood? what does this mean?

Answer 62

the right side carries deoxygenated blood which needs to be oxygenated SO they get pumped to the lungs the left side carries oxygenated blood (fresh from the lungs) which is needed by tissues of the body

Question 63

describe the pressures experienced by the blood in the different chambers of the heart? why do they differ?

Answer 63

the blood in the atria (upper chambers) experiences low pressures as they just need to be pumped to the ventricles (lower chambers) the blood in the ventricles experiences much higher pressure as they need to be pumped to different organs and tissues in the body

Question 64

why do ventricles of the heart have thicker walls than the atria?

Answer 64

the blood in the ventricles experiences much higher pressure as they need to be pumped to different organs and tissues in the body - hence, thicker walls to pump the blood with more force

Question 65

what is the purpose of valves in the heart?

Answer 65

to prevent the backflow of blood the valves only open under pressure and then close

Question 66

what are the (4) valves in the heart? where are they?

Answer 66

tricuspid: between the right atrium and right ventricle pulmonary: between right ventricle and pulmonary arteries mitral (bicuspid): between the left atrium and left ventricle aortic: between the left ventricle and aorta

Question 67

differentiate between arteries and veins

Answer 67

veins carry blood to heart (deoxygenated) arteries carry blood away from the heart (oxygenated) the pulmonary circuit is an exception - pulmonary veins carry oxygenated blood - pulmonary arteries carry deoxygenated blood

Question 68

what is the aorta?

Answer 68

a really thick muscular artery that distributes blood from the left ventricle to the rest of the body really strong: can withstand high pressure of blood pumped from the heart

Question 69

how many heart chambers do fish have?

Answer 69

2 heart chambers: 1 atrium and 1 ventricle

Question 70

how many heart chambers do amphibians have?

Answer 70

3 heart chambers: 2 atria and 1 ventricle

Question 71

how many heart chambers do reptiles have?

Answer 71

3 heart chambers: 2 atria and 1 ventricle

Question 72

how many heart chambers do birds have?

Answer 72

4 chambers: 2 atria and 2 ventricles

Question 73

what's the exception to the heart chamber rule for reptiles?

Answer 73

normally, reptiles have 3 heart chambers (2 atria and 1 ventricle) BUT alligators and crocodiles have 4 heart chambers

Question 74

what are the (2) pathways of the circulatory system?

Answer 74

pulmonary: blood pumped to and from lungs systemic: blood pumped to and from tissues of the body

Question 75

what are the steps of pulmonary circulation?

Answer 75

blood is pumped from the right ventricle - thru the pulmonary valve - to the pulmonary arteries blood gets reoxygenated at the capillaries/alveoli of the lungs where gas exchange occurs blood travels back to the heart's left atrium via pulmonary veins

Question 76

where in the body does blood have the lowest oxygen concentration?

Answer 76

pulmonary artery blood has been depleted of all its nutrients and oxygen by the rest of the body by the time it has reached the pulmonary artery

Question 77

where in the body does blood have the highest oxygen concentration?

Answer 77

pulmonary vein blood was just supplied with fresh oxygen from the lungs

Question 78

what are the steps of systemic circulation?

Answer 78

left atria contracts and pushes blood thru the mitral valve to left ventricle left ventricle contracts (very strong) and blood travels thru the aortic valve to aorta blood from aorta travels to entire body blood reaches the capillaries (capillary beds) in the tissues of the body. the cells surrounding the capillaries absorb the nutrients and oxygen from the arterial end and unload carbon dioxide and waste into the venous end of the capillaries veins carry the blood back to the superior and inferior vena cava which empty it into the right atrium blood from the right atrium goes thru the tricuspid valve into the right ventricle

Question 79

what are the (2) phases to heart contraction?

Answer 79

systole: when the heart contracts, squeezing out blood diastole: when the heart relaxes after a contraction

Question 80

what starts a heart contraction? what initiated our heartbeat and how is that electrical signal spread?

Answer 80

a group of cells called the sinoatrial node (aka SA node aka pacemaker) which can generate their own electrical impulse they initiate our heartbeat by depolarizing and spreading an electrical signal. the electrical signal spreads smoothly from one cardiac muscle cell to another connecting these cardiac muscle cells at the intercalated discs are gap junctions which allow ions to flow smoothly from one cell to another - allows the electrical signal to move in a coordinated way ------ the electrical signal begins at the SA node. this electrical signal causes both of the atria to contract as it spreads thru out the walls of the atria the electrical signal arrives at the AV node (atrio ventricular node). there's a bit of delay to make sure the blood has been completely ejected from the atria to fill the ventricles. the electrical signal will travel from the AV node down thru cells called the Bundle of His (which is in the septum between the lower ventricles) when the electrical signal hits the bottom, it branches upwards and outwards thru the cell walls of the ventricles via Purkinje Fibers. this causes both ventricles to contract simultaneously

Question 81

what are the (6) phases of the cardiac cycle mapped out on the electrocardiogram - the heartbeat monitor thingy?

Answer 81

P-wave: represents the electrical signal of the atria contracting. after the P-wave QRS-complex: big spike due to the ventricles contracting/depolarizing (which hides the atria repolarizing) after the QRS-complex T-wave: represents the ventricles repolarization to prepare for another contraction after the T-wave REFER TO DIAGRAMS

Question 82

describe this relationship: cardiac output = stroke volume x heart rate

Answer 82

cardiac output: volume of blood that gets pushed out of the ventricles in 60 seconds stroke volume: volume of blood that gets pushed out of the ventricles per contraction heart rate: number of contractions your heart has per minute

Question 83

describe this relationship: stroke volume = end diastolic volume - end systolic volume

Answer 83

the reason for this formula is because when ventricles contract, they don't push out 100% of the blood they hold ---- stroke volume: volume of blood that gets pushed out of the ventricles per contraction end diastolic volume: how much blood in the ventricle before the contraction end systolic volume: how much blood in the ventricle after the contraction

Question 84

describe this relationship: blood pressure = cardiac output x systemic vascular resistance

Answer 84

blood pressure: pressure exerted by circulating blood onto the vessel walls cardiac output: volume of blood that gets pushed out of the ventricles in 60 seconds -- the more blood pushed out of the heart per minute, more pressure onto walls systemic vascular resistance: measure of resistance to flow of blood. influenced by diameter of blood vessels and blood viscosity

Question 85

what factors influence systemic vascular resistance?

Answer 85

influenced by diameter of blood vessels and blood viscosity ---- systemic vascular resistance: measure of resistance to flow of blood

Question 86

which type of blood vessel is the thickest and why?

Answer 86

arteries they must withstand the highest pressure to pump blood to the rest of the body

Question 87

describe the pathway blood travels in terms of blood vessels

Answer 87

from the heart arteries arterioles capillaries (where gas exchange occurs) veinules veins

Question 88

describe the composition of arteries (its layers)

Answer 88

FROM OUTERMOST TO INNER!!! connective tissue layer which strengthens the artery and allows it to attach to nearby tissue thick muscular layer of smooth muscle. it contracts/relaxes to regulate the diameter of the artery. also allows artery to withstand the high pressure of blood being pumped with a lot of force from the heart elastic layer. gives the artery flexibility to stretch and withstand the pressure of the blood layer of endothelium cells. allows the blood to flow easily TO SUMMARIZE, arteries are large, muscular, and elastic

Question 89

describe the composition of arterioles (its layers)

Answer 89

connective tissue layer which strengthens the arteriole and allows it to attach to nearby tissue smooth muscle layer in between (thinner here than in the artery but for its proportion, arterioles have a thicker one... hence able to exert more control with diameter and blood pressure here) inner layer of endothelial cells. allows the blood to flow easily

Question 90

describe the composition of capillaries (its layers)

Answer 90

ONLY ONE LAYER a single-celled layer of endothelium -- allows for oxygen and nutrients and waste to diffuse easily

Question 91

what are the (2) types of blood pressure forces at work in the capillaries? describe them and how they work together

Answer 91

hydrostatic: pressure from the fluid inside the vessels pushing up against the blood vessel wall - wants to move things out of the capillaries oncotic: works in the opposite direction. pressure from the proteins in the blood attracting water from outside the vessel. it pulls things like extra fluids, waste product, and CO2. hydrostatic pressure and oncotic is present in every part of a blood vessel. but the amount of each varies. in the arterial side of the capillaries, hydrostatic pressure is high = net filtration of fluids and small molecules get pushed out into the tissue space note that oncotic pressure stays the same in the venous end, hydrostatic pressure is lower than oncotic = net movement back into the capillaries = reabsorption

Question 92

what are precapillary sphincters?

Answer 92

rings of muscle that contract to clamp down and block blood vessels or relax to let blood flow more easily can control where blood goes. this selective blood flow is helpful to stop blood for going to certain tissues depending on body's needs

Question 93

describe the composition of veinules (its layers)

Answer 93

outer layer of thin connective tissue thin muscle layer in the middle endothelium layer on the inside

Question 94

describe the composition of vein (its layers)

Answer 94

connective tissue outer layer muscle layer (thin because pressure is very low here) elastic layer inner endothelium layer

Question 95

how do veins make sure blood reaches the heart considering the low pressure it has?

Answer 95

one way valves that prevent back flow backwards due to gravity also assisted by skeletal muscle contractions to propel the blood forward blood will eventually reach the superior and inferior vena cava