S&F Blood Vessels

Question 1

What are the main types of blood vessels?

Answer 1

Arteries, Veins, Capillaries

Each type has distinct functions and structures.

Question 2

What are the three layers of blood vessel structure?

Answer 2

Tunica adventitia, Tunica media, Tunica intima

These layers contribute to the overall function and resilience of blood vessels.

Question 3

What is the function of the tunica intima?

Answer 3

It consists of:
- endothelium = simple squamous epithelium

• basal lamina (basement membrane) of the epithelium cells
• subendothelial connective tissue = provides smooth surface for blood flow

This layer is crucial for smooth blood flow.

Question 4

What is the primary function of arteries?

Answer 4

Carry blood under high pressure

This requires thicker walls compared to veins.

Question 5

True or False: Veins have valves to prevent backflow.

Answer 5

True

Valves are important for maintaining unidirectional blood flow.

Question 6

What is the diameter range of muscular arteries?

Answer 6

0.5 mm to 0.4 cm

These arteries distribute blood to muscles and organs.

Question 7

What distinguishes elastic arteries from muscular arteries?

Answer 7

Elastic arteries have a thick tunica media with many elastic fibers

They help withstand pressure changes during the cardiac cycle.

Question 8

What is the diameter of arterioles?

Answer 8

Less than or equal to 30 μm

Arterioles are critical in controlling blood flow and pressure.

Question 9

Fill in the blank: Capillaries connect ______ and ______.

Answer 9

arterioles, venules

Capillaries facilitate gaseous exchange.

Question 10

What type of capillaries have pores for rapid exchange?

Answer 10

Fenestrated capillaries

These are found in areas requiring quick absorption, like the kidneys.

Question 11

What are sinusoidal capillaries characterized by?

Answer 11

Spaces between endothelial cells and incomplete or absent basement membrane

This structure allows for the exchange of large solutes.

Question 12

What role do precapillary sphincters play?

Answer 12

They guard the entrance to each capillary

Their contraction and relaxation control blood flow into capillary beds.

Question 13

What is the classification of veins based on size?

Answer 13

Small (<2mm), Medium (2-9mm), Large (>9mm)

E.g. of large = superior and inferior vena cava

The classification helps in understanding their function and structure.

Question 14

What is the primary role of venules?

Answer 14

Collect blood from capillary beds and deliver it to small veins

Venules have a low-pressure system.

Question 15

What are the three anatomical planes?

Answer 15

Coronal/ frontal = passes from side to side splitting body into front and back

Transverse = splits the body into upper and lower parts

Sagittal = passes from front to back splitting body into right and left sides

These planes are used to describe locations and movements in the body.

Question 16

What does the coronal plane divide?

Answer 16

Front and back of the body

It runs from side to side.

Question 17

True or False: The transverse plane splits the body into upper and lower parts.

Answer 17

True

This plane is also known as the horizontal plane.

Question 18

What is a metarteriole?

Answer 18

A vessel supplying a single capillary bed

Constriction of the metarteriole can reduce flow to a whole capillary bed

It leads directly to a vein and has many capillaries branching off.

Question 19

What is the function of arteriovenous anastomoses?

Answer 19

Direct communication between arteriole and venule

They allow blood to bypass the capillary bed and flow directly to venous circulation when dilated.

Question 20

What do all blood vessels have?

Answer 20

An arterial supply and a venous drainage

Question 21

What must all blood vessels be?

Answer 21

Resilient

Flexible

Always remain open

Question 22

What is the typical blood vessel structure?

Answer 22

Lumen

Tunica intima

Tunica media

Tunica adventitia/ external

Question 23

Describe the tunica media

Answer 23

Smooth muscle fibres in loose connective tissue

May contain elastic fibres

Question 24

Describe the tunica Adventia/ externa

Answer 24

Connective tissue

Merges with surrounding connective tissue (i.e. artery & vein are parallel so connective tissue will overlap)

May contain vaso vasorum (for large vessels)

Question 25

What are the features of the Tunica Intima? 4 marks

Answer 25

- Inner layer of blood vessel - Endothelial lining - Surrounding layers of connective tissue - Variable numbers of elastic fibres

Question 26

What are the features of the Tunica Media? (7 marks)

Answer 26

- Middle layer of blood vessel - Sheets of smooth muscle tissue in framework of loose connective tissue - Collagen fibres connect the 3 layers - Thickest layer - Separated from tunica externa by elastic fibres called the external elastic membrane - Smooth muscle cells encircle the endothelium that lines the lumen - Large arteries also have arranged smooth muscle

Question 27

What are the features of the Tunica Adventia/Externa? (5 marks)

Answer 27

- Outer layer of blood vessel - Made up of connective tissue - In arteries, has collagen fibres with scattered bands of elastic fibres - In veins, it is thicker than the tunica media and contains a network of elastic fibres and bundles of smooth muscle cells - The connective tissue blend into those of adjacent tissues to stabilise and anchor the blood vessel

Question 28

Outline the blood vessel structure of an artery

Answer 28

General appearance = usually round with relatively thick wall **Tunica Intima** - Endothelium = usually rippled due to vessel constriction - Internal Elastic membrane is present **Tunica Media** - Is thick and dominated by smooth muscle cells and elastic fibres - External elastic membrane is present **Tunica Externa** - Has collagen & elastic fibres

Question 29

Outline the blood vessel structure of a vein

Answer 29

General appearance = usually flattened or collapsed with relatively thin wall **Tunica Intima** - Endothelium = often smooth - Internal elastic membrane is absent **Tunica Media** - Is thin and dominated by smooth muscle cells and collagen fibres - External elastic membrane is absent **Tunica Externa** - Has collagen & elastic fibres and smooth muscle cells

Question 30

What is the primary function of veins?

Answer 30

Carry blood under low pressure to the heart Have thin walls and may have valves to prevent backflow Low pressure system Easily distensible (capacitance) = can hold more blood

Question 31

Compare veins to arteries (5 marks)

Answer 31

Artery: -has a thicker wall -appears to have a small lumen -maintains its shape -is more resilient -does not contain valves

Question 32

What are the 3 types of arteries?

Answer 32

Elastic (conducting) Muscular (distributing) Arterioles (resistance vessels)

Question 33

Describe Elastic (conducting) arteries

Answer 33

E.g. aorta, brachiocephalic & common carotid - Diameter = up to 2.5cm - Withstands changes in pressure during the cardiac cycle and ensures continuous blood flow when heart contracts/relaxes **Structural adaptations** - Thick tunica media - With many elastic fibres (can withstand highest blood pressure in the body) - Few smooth muscle cells

Question 34

Describe Muscular (distributing) arteries

Answer 34

E.g. brachial & femoral - Diameter = 0.5mm - 0.4cm - Distribute blood to muscles and organs - Capable of vasodilation and vasoconstriction in order to control the rate of blood flow to suit the needs of the organ **Structural adaptations** - Lots of smooth muscle cells in tunica media - Distinct internal (IEL) & external (EEL) elastic laminae - Thick tunica media

Question 35

Describe arterioles (resistance vessels)

Answer 35

- Diameter = <30 um - Capable of vasodilation and vasoconstriction - Control blood flow to organs - Involved in blood pressure control - Main control point for blood flow into the capillary beds **Structural adaptations** - One to two layers of smooth muscle cells in tunica media - Poorly defined tunica externa

Question 36

What are capillaries?

Answer 36

- Smallest blood vessel - Connect arterioles and venules - Site of gaseous exchange - Thin walls facilitate diffusion - Blood flow through capillaries is slow - Structure permits 2-way exchange (fluid moves in and out) - 8 um in diameter - Found near almost every cell

Question 37

What are the different types of capillaries?

Answer 37

Continuous Fenestrated Sinusoidal

Question 38

What are continuous capillaries?

Answer 38

- Majority of capillaries are continuous - Cells are all next to each other with no gaps - E.g. skeletal and smooth muscle, CT and the lungs

Question 39

What are fenestrated capillaries?

Answer 39

- These are more permeable - Pores penetrate the endothelial lining - Rapid exchange of water or large solutes (e.g. small peptides) - Involved in absorption - Found in kidney, choroid plexus and endocrine glands

Question 40

What are sinusoidal capillaries?

Answer 40

- These are leakier - In spaces between endothelial cells - Incomplete or absent basement membrane - Exchange of large solutes i.e. plasma proteins - Found in specialised lining cells (e.g. in the liver, phagocytic cells engulf damaged RBCs) - Blood moves slowly through sinusoids

Question 41

What is flow through the capillary beds controlled by?

Answer 41

Metarterioles Precapillary sphincters Arteriovenous anastomoses

Question 42

What is the role of precapillary sphincters?

Answer 42

Guard the entrance to each capillary Contraction narrows entrance = reduced flow Relaxation dilates entrance = increased flow

Question 43

What are the structural adaptations of venules?

Answer 43

- Smallest vein - Diameter = varies, average 20 um - Small = endothelium on basement membrane - Larger = increasing number of smooth muscle cells located outside of endothelium

Question 44

What are structural adaptations of veins?

Answer 44

- Thin walled - Tunica externa is predominant - Valves to aid blood flow from lower parts of body moving up (facilitate one-way blood flow)