lecture 7 - capillaries & lymphatics

Question 1

What is the relative thickness of capillary walls?

Answer 1

Very thin, to allow for easy exchange of gases and nutrients.

Question 2

Why do capillary beds have a large total cross sectional area?

Answer 2

To maximise the rate of exchange at low pressure, speed and flow.

Question 3

How do capillaries ensure slow and smooth flow of blood, despite the pulsatile pumping of the heart?

Answer 3

They slow down the blood and it is at low pressure

Question 4

What is the basic structure of a capillary?

Answer 4

A tube formed by simple squamous epithelia, surrounded by a basement membrane

Question 5

What is the diameter of a capillary?

Answer 5

The same size as a red blood cell

Question 6

What feature controls the flow into capillary beds?

Answer 6

Pre-capillary sphincters

Question 7

What are pre-capillary sphincters?

Answer 7

Smooth muscle cells that circumferential around the start of the capillary beds, and contract to limit flow into the beds.

Question 8

What vessels supply the capillary beds?

Answer 8

Terminal arterioles

Question 9

What feature of a capillary bed directs blood straight through the thoroughfare channel?

Answer 9

Vascular shunts

Question 10

What is the function of vascular shunts?

Answer 10

They direct blood through a large thoroughfare channel, rather than into all the different parts of the capillary bed.

Question 11

What are the 3 types of capillary?

Answer 11

Continuous, Fenestrated, Sinusoidal

Question 12

What is the most widespread type of capillary?

Answer 12

Continuous

Question 13

What are the components of a capillary that vary to control permeability?

Answer 13

Basement membrane, intercellular cleft, endothelial layer/tunica intima

Question 14

What is the structure of a continuous capillary?

Answer 14

Continuous endothelial layer and basement membrane, which only allow small molecules to pass through

Question 15

What is the basement membrane of a capillary?

Answer 15

Also called the basal lamina, it is a layer of extracellular matrix that forms the outmost layer, that molecules must pass through.

Question 16

What is the approximate diameter of a continuous capillary?

Answer 16

8-10µm

Question 17

What is the structure of fenestrated capillaries?

Answer 17

Capillaries with small pores/fenestrations in the endothelial layer that allow molecules to pass out. However, they have a continuous basement membrane that molecules must pass through.

Question 18

Do fenestrated capillaries have continuous or discontinuous basement memebrane?

Answer 18

Continuous

Question 19

What type of capillary are commonly found in the kidneys and small intestines?

Answer 19

Fenestrated capillaries

Question 20

What is the leakiest type of capillary?

Answer 20

Sinusoidal

Question 21

What is the structure of a sinusoidal capillary?

Answer 21

Has large intercellular gaps between endothelial cells and an incomplete basement membrane that allows for direct exchange of plasma with the ECM.

Question 22

What capillary type has the largest diameter?

Answer 22

Sinusoidal

Question 23

What is the diameter of a sinusoidal capillary?

Answer 23

30-40µm

Question 24

What are 4 key functions of the lymph vascular system?

Answer 24

Drains excess tissue fluid & plasma proteins and returns to blood, filters foreign materials, screens lymph for antigens and releases antibodies, absorbs fat from intestines and transports to the blood.

Question 25

How is fat absorbed using the lymph vascular system?

Answer 25

At the intestines, fat that has been consumed is absorbed by lymphatic drainage vessels and transported to the blood via lymph channels

Question 26

How do lymphatic vessels originate?

Answer 26

Commence as large, blind ended capillaries

Question 27

In the small intestine, what lymphatic vessels initially drain fat-laden lymph?

Answer 27

Lacteals

Question 28

Where do lacteals drain fat-laden lymph to?

Answer 28

lymphatic fat collecting vessel called the cisterna chyli.

Question 29

Why do lymphatic vessels have valves?

Answer 29

To maintain unidirectional flow.

Question 30

Why are lymph channels transparent/hard to spot?

Answer 30

Very thin walled with transparent fluid flowing through them as contain no red blood cells.

Question 31

Is fluid at high or low pressure in lymphatic vessels?

Answer 31

Low pressure

Question 32

What are the 3 major regions of lymph nodes?

Answer 32

Cervical, Axillary, Inguinal

Question 33

Where are cervical lymph nodes located?

Answer 33

The neck

Question 34

Where are axillary nodes located?

Answer 34

In the armpit (axilla)

Question 35

Where are inguinal nodes located?

Answer 35

In the groin

Question 36

Where does the right lymphatic duct drain?

Answer 36

The right subclavian vein

Question 37

Where does the thoracic duct drain?

Answer 37

The left subclavian vein and internal jugular vein

Question 38

What is the process of fat absorption in the small intestine vili (Cardio vascular system)?

Answer 38

Lacteals (lymphatic vessels) absorb fats and then send them to the portal veins which take nutrient-rich blood to the liver

Question 39

What vessels drain the lymph nodes?

Answer 39

Efferent lymphatic vessels

Question 40

Where are immune cells held in a lymph node?

Answer 40

They hang onto a matrix of fibres, surveying the lymph fluid

Question 41

How does cancer often spread from the breasts into others parts of the body?

Answer 41

Via the breast tissue lymphatic drainage system that carries cancer cells into the blood vascular system, facilitating metastasis