Case 1- Lymphatics and blood vessels

Question 1

Organisation of lymph vessels

Answer 1

Lymph travels along lymphatic vessels which connect to lymphoid organs. The afferent lymphatics take lymph to the lymph nodes and the efferent lymphatics take it away. The organ plexus (capillary system within organs) drains lymph into the lymphatic vessels. Most lymph drains via the thoracic duct. Lymph drains into the venous system at the left venous angle

Question 2

Function of lymphatic system

Answer 2

1) Drains interstitial fluid- between cells, eventually returns to venous system
2) Transport of dietary lipids- transported as chyomicrons,
3) Immune response- act as a phagocytic filter, preventing unwanted particles entering blood circulation.

Question 3

Function of lymph nodes

Answer 3

Provide a site for lymphocytes to come into contact with antigens, increasing immune response through lymphocyte proliferation

Question 4

Structure of lymph vessels

Answer 4

Contain microvalves between the cells of the wall, tiny gaps which can be open or closed. Allow fluid to move between the lymphatics and the interstitium. Valves to prevent backflow at low pressure.

Question 5

How is lymphatic fluid maintained

Answer 5

Maintained by hydrostatic pressure between the interstitial fluid and lymph. This is the pressure difference between the interstitial fluid and the lymph. Regulates expansion phase and compression phase.

Question 6

Expansion phase

Answer 6

Pressure in the interstitium (extracellular space) is higher than in the lymphatic, primary microvalves open and secondary valves close. Fluid flows from the interstitium to the lymphatic.

Question 7

Compression phase

Answer 7

Pressure in the lymphatic is higher than in the interstitium, the primary microvalves close and the secondary valves open. The lymph travels along the lymphatic.

Question 8

Lymph node structure

Answer 8

Bean shaped. They are split into cortex’s which are then divided, from the outside in into the cortex follicle, the paracortex and the medulla. The Cortex is surrounded by the subcapsular sinus which is surrounded by the capsule. In the capillary bed there are postcapillary (high endothelial) venules, this is where the lymphocytes enter the lymph nodes into the cortex and paracortex, and where the blood supply comes from.

Question 9

Passage of lymph through the lymph node

Answer 9

The afferent lymphatic enters the lymph node. The lymph will then drain through the subcapsular sinus and medullary sinus and into the efferent lymphatic, some will go through the cortex

Question 10

Functional properties of the structures in the lymph nodes

Answer 10

1) The paracortex contains high endothelial venules which drain lymphocytes into the paracortex, they then move to the cortex to form follicles of tightly packed lymphocytes.
2) The follicles are where lymphocytes come into contact with antigens. When an antigen is recognised the lymphocytes proliferate to produce an immune response.
3) The lymphocytes then travel through the medullary cords into the medullary sinus and efferent lymphatics, where they will be transported out of the lymph node.

Question 11

Lymph node cortex

Answer 11

The follicles consist of a germinal centre (maturing B cells) containing lymphocyte aggregation surrounded by the mantle zone (lymphocytes and T cells)

Question 12

Types of lymphoid tissue

Answer 12

• Thymus- T-cell development and maturation
• Spleen- Filters and is the site of immune response, destroys erythrocytes (red blood cells)
• Tonsils, Adenoids, Appendix- Contain lymphoid follicles
• Bone marrow- produces B-cells, T-cells and macrophages
• Lymph node
• Peyer’s patches

Question 13

How lymph travels through your lower limbs

Answer 13

From the inguinal nodes, through the iliac then aortic node and into the cisterna chyle. Now contains fatty chyle from the gut, then into the thoracic duct

Question 14

How lymph travels through your left arm

Answer 14

Through the axillary nodes into the subclavian trunk and and into the left venous angle

Question 15

How lymph travels from your head and neck

Answer 15

Through the jugular trunk

Question 16

How does lymph drain from the right side of your body

Answer 16

Into the right lymphatic trunk

Question 17

What drains into the left venous angle

Answer 17

Left side of your body, lower limbs and trunk (after it goes through the thoracic duct

Question 18

Vasoconstriction

Answer 18

Reduces the diameter of blood vessels increasing blood pressure and resistance causing blood flow to decrease

Question 19

Vasodilation

Answer 19

When the smooth muscle relaxes, it increases the diameter of the blood vessels. Resistance decreases and blood flow increases

Question 20

Local factors that effect arteriole diameter

Answer 20

Metabolic: the production of CO2 will cause vasodilation which will increase blood flow, removing CO2 and bringing O2.
Myogenic factors refer to the blood vessel itself which means that when it stretches, due to an increase in blood pressure, it will try and constrict (vasoconstriction).

Question 21

External factors that affect blood diameter

Answer 21

Autocrine system, when there is a sympathetic activation it will cause vasoconstriction in the GI tract and Kidneys reducing blood flow.
Endocrine system, when epinethrin, ADH, angeotensin 2 are released they can increase the blood pressure.

Question 22

4 starting forces for tissue fluid formation

Answer 22

Capillary hydrostatic pressure
Capillary oncotic pressure
Interstitial fluid hydrostatic pressure
Interstitial fluid oncotic pressure

Question 23

How is tissue fluid formed

Answer 23

Due to the leaky nature of the capillaries some of the fluid will leak out into the external space to become tissue fluid. The more blood pressure there is the more fluid that will leak out.

Question 24

Capillary filtration

Answer 24

Filtering the fluid out of the capillary into the surrounding. Tends to happen at arteriole end of capillary. Effected by capillary hydrostatic pressure and interstitial fluid oncotic pressure

Question 25

Capillary reabsorption

Answer 25

Reabsorb the fluid from the surroundings back into the capillary. Tends to happen at venuous end of capillary. Effected by capillary oncotic pressure and interstitial fluid hydrostatic pressure.

Question 26

What is vascular resistance

Answer 26

The force that impedes blood flow through the circulation

Question 27

What affects vascular resistance

Answer 27

Blood viscosity and vessel length. Vessel radius is the most important factor, when the radius decreases by half the resistance increases by 16 times

Question 28

Blood flow through an organ

Answer 28

Arranged in series. If blood resistance increases in an arteriole or vein, blood resistance in the series will increase as a whole. The total blood resistance in the series will be the total blood resistance in all the blood vessels added together

Question 29

Blood flow through different organs

Answer 29

Arranged in a parallel structure. The resistance in one organ will not affect the other organs, this is advantageous

Question 30

Blood resistance in the different vessels

Answer 30

The arterioles are called the resistance vessel because it offers resistance to blood flow and can adjust this. The vein is the compliance vessel because it can accommodate a large volume of blood without changing blood pressure. The capillaries are also called the site of exchange, as substances are exchanged here between the tissue fluid and blood.

Question 31

Volume of blood flow equation (Q)

Answer 31

``` Q= P/R P= pressure gradient R= resistance ```

Question 32

Velocity of blood flow equation (V)

Answer 32

``` V= Q/A Q= blood flow A= cross sectional areas, this increases in branching and decreases in merging. Blood flow slowest as capillaries which have the biggest cross-sectional area ```

Question 33

Distribution of blood flow at rest

Answer 33

GI- 20-25% Kidneys- 20% Brain- 15% Skeletal muscle- 15-20%

Question 34

Distribution of blood flow when exercising

Answer 34

Skeletal muscle- 80-85% Blood to other organs is greatly reduced. Blood is distributed according to metabolic needs at rest this is digestion and excretion. When exercising skeletal muscles will have a higher metabolic need

Question 35

Blood pressure

Answer 35

The pressure exerted by the blood on the inner wall of the blood vessels. Regulated by baroreceptors in the short term and RAAS in the long term.

Question 36

Systolic blood pressure

Answer 36

Blood pressure when the heart contracts (SBP)

Question 37

Diastolic blood pressure (DBP)

Answer 37

Blood pressure when the heart relaxes

Question 38

Pulse pressure

Answer 38

Systolic minus diastolic blood pressure

Question 39

Mean arterial pressure

Answer 39

(MAP)= DBP + 1/3 (SBP-DBP). This equation is not just an average of SBP and DBP because the blood vessels are in DBP for a longer time.

Question 40

High pressure baroreceptors

Answer 40

Located in the wall of the aortic arch and in the carotid sinus, where blood pressure is high. They detect blood pressure from 60 to 180 mm Hg. When arterial blood pressure increases they stretch their walls more. The more the baroreceptor is stretched, the more action potentials are fired, this will then be sent to the CNS.

Question 41

Low pressure baroreceptors

Answer 41

Found between pulmonary vein and atrium and near the vena cava. They respond to blood volume not pressure. When Increased blood volume in the vena cava is detected by the baroreceptors, they will stimulate an increase in heart rate which increases cardiac output. This will increase renal perfusion (blood flow to the kidneys) and increased Na+ and water excretion. In the atria when there high blood volume the low pressure barometers will stimulate the secretion of atrial natriuretic peptide (ANP). This causes vasodilation which decreases vascular resistance, this increases renal perfusion, meaning more water and Na+ is excreted

Question 42

Cardiac output

Answer 42

The volume of blood pumped out the ventricle per minute. When cardiac output increases resistance decreases to maintain MAP. through vasodilation

Question 43

What do the blood vessels do when resistance increases

Answer 43

Vasoconstriction will increase so that cardiac output decreases to maintain a constant MAP Mean arterial pressure= cardiac output x total peripheral resistance

Question 44

Compliance in blood vessels

Answer 44

Describes the ease of stretching a vessel wall. If a vessel is compliant it means it can accommodate a larger volume without changing the pressure much, veins are more compliant then arteries. Sympathetic stimulation, vasoconstrictors (e.g. epinethrine) and aging decrease the compliance of blood vessels.

Question 45

The walls of the blood vessels

Answer 45

From inside out tunica intima, tunica media and tunica adventitia/ externa

Question 46

Tunica intima

Answer 46

The inner layer of the blood vessels, its made of squamous epithelium cells as well as connective tissue. Very smooth to minimise friction

Question 47

Tunica media

Answer 47

Contains lots of smooth muscle, collagen and elastic fibre. The thickest wall in the arteries

Question 48

Tunica adventitia/externa

Answer 48

Contains elastic fibre and lots of collagen fibres. In veins its the thickest layer

Question 49

External elastic lamina

Answer 49

A distinct layer of connective tissue in large blood vessels. The inner one separates the tunica media and the tunica intima, the outer one separates the tunica media and the tunica externa. Amount of elastin determine the structure.