Blood vessels

Question 1

What are the layers of blood vessels? (from inner to outer)

Answer 1

1. tunica intima
2. tunica media
3. tunica adventitia

Question 2

What are the distinguishing features of the tunica intima layer?

Answer 2

It consists of endothelium, a subendothelial coat, and internal elastic lamina.
The endothelium has squamous cells lining the lumen on the basement membrane and prominent nuclei bulging into the lumen.
The subendothelial coat has fibroelastic connective tissue, fibroblasts and myointimal cells orientated parallel to the long axis of the vessel.
The internal elastic lamina is made of elastic fibres.

Question 3

What are the distinguishing features of the tunica intima layer?

Answer 3

It is a mixture of circularly arranged smooth muscle cells, collagen and elastic fibres and fibroblasts. In large vessels, it has nerves called Nervi vasorum and a blood supply called vasa vasorum

Question 4

What are the distinguishing features of the tunica adventitia layer?

Answer 4

It is made of external elastic lamina and dense fibroelastic tissue.
The external elastic lamina is not always obvious. The dense fibroelastic tissue blend with the surround connective tissue and have Nervi and vasa vasorum throughout this layer.

Question 5

What are the types of arteries?

Define the types of arteries

Answer 5

1. conducting (elastic) arteries = large artery with wide lumen, conducting large volumes of blood around the body
2. distributing (muscular) arteries = small + medium sized arteries carrying blood to specific tissues with thick walls compared to luminal volume
3. arterioles = principle site for control of total peripheral vascular resistance and where blood pressure is reduced to Leo levels in capillaries

Question 6

What are the layers in the conducting arteries?

Answer 6

• tunica intima = all elements present
• tunica media = mostly elastic fibres but have fine collagen fibres, fibroblasts and smooth muscle in between
• tunica adventitia = no distinct external elastic lamina + blends with surrounding tissue

Question 7

What are the layers in the distributing arteries?

Answer 7

All three layers present

• elastic laminate wall defined
• tunica media consists of thick layer of smooth muscle

Question 8

What are the layers in the arterioles?

Answer 8

• tunica intima lacks subendotheial coat
• tunica media has only 1-3 layers of smooth muscle cells
• tunica adventitia has no external elastic lamina + connective tissue blends with surrounding tissue

Question 9

What is the main function of capillaries?

What is the general structure of capillaries?

Answer 9

Site of exchange of metabolites and waste products with tissues
Diameter less than 10um = allowing passage of single blood cell

It has endothelial cells lining the basement membrane which is surrounded by loose connective tissue

Question 10

What are the types of capillaries?

Answer 10

• continuous capillaries
• fenestrated capillaries
• sinusoidal capillaries
• sinusoids
• sinuses

Question 11

Define continuous capillaries and where they are found?

Answer 11

They have no pores or interruptions between endothelial cells
They are found in muscles, lungs, and nervous tissue

Question 12

Define fenestrated capillaries and where they are found?

Answer 12

They have pores scattered throughout the endothelial cells
They are found in endocrine glands, intestines and glomerular capillaries of the kidneys, and sites where fluid transport is important

Question 13

Define sinusoidal capillaries and where they are found?

Answer 13

They are larger and more irregular shaped with no distinct basement membrane
They are found in endocrine organs, aortic and carotid bodies

Question 14

Define sinusoids and where they are found?

Answer 14

They are larger than sinusoidal capillaries, the basement membrane is mostly absent with gaps in the walls through which large molecules, including proteins, may be exchanged
They are found in bone marrow and the liver
Hepatic sinusoids have associated marcophages

Question 15

Define sinuses and where they are found?

Answer 15

They are larger than sinusoids with a discontinuous basement membrane
They are found in the spleen

Question 16

What are the types of veins?

Answer 16

• venules
• small and medium veins
• large veins

Question 17

What do venules consist of?

Answer 17

They are lined by endothelial cells associated with loose connective tissue

Question 18

What do small and medium veins consist of?

Answer 18

They have increasing smooth muscle but are considerably less muscular than arteries.
They have thin tunica intima and media surrounded by wall developed tunica adventitia. These veins may have valves formed by invaginations of tunica intima to ensure unidirectional blood flow

Question 19

What do large veins consist of?

Answer 19

Tunica intima is thicker and may be internal elastic lamina
Tunica media is mainly collagen and elastic fibres but may have some smooth muscle
Tunica adventitia is the thickest part of the wall with fibroelastic tissue present and no valves in the largest veins

Question 20

How is blood supply to individual organs regulated?

What do arterioles provide?

Why is there structure of capillaries important?

Answer 20

It is regulated by the autonomic nerves which control the smooth muscle in distribution arteries

They provide resistance to pulse pressure reducing it to very low levels in capillaries

Capillary strucurtre allows the exchange of nutrients and wast products across large surface areas

Question 21

What is venous return aided by?

Answer 21

• muscular pump = as locomotor muscles of the limbs contract, external pressure is applied to large veins
• respiratory pump = during inspiration, -ve pressure in thorax aids the return of blood to the heart and the valves prevent back flow in veins
• cardiac pump = some remaining low +ve blood pressure in great veins returning to the heart

Question 22

What branches arise from the aorta?

What are the first branches of the aorta before the brachiocephalic trunk?

Answer 22

Dorsal, lateral and ventral branches

Coronary arteries

Question 23

Define the dorsal branches and where they supply to?

Answer 23

These branches are arranged in segmental pairs
They supply the developing signal cord and epaxial structures such as intercostal arteries in the thorax and lumbar arteries in the abdomen

Question 24

Define the lateral branches and where they supply to?

Answer 24

They are paired by irregularly segments
They are phrenicoabdominal, renal, ovarian/testicular and deep circumflex iliac arteries and external iliac arteries = supplying the hind limbs
They also have paired foetal umbilical arteries which persist in mature animals as the internal iliac arteries which supply the pelvic region and round ligament of the bladder

Question 25

Define the ventral branches and where they supply to?

Answer 25

They are arranged singularly and irregularly segmented
Single branches in the thorax are from the bronchoeophageal arteries.
In the abdomen, the foetal vitelline arteries to yolk sac persist as the cranial mesenteric artery and other ventral branches are the coeliac and caudal mesenteric arteries