Histo Vessels

Question 1

What are the three layers or coats that make up the wall of blood and lymphatic vessels?

Answer 1

Tunica Intima, Tunica Media, and Tunica Externa (Adventitia).

Question 2

What is the structure of the tunica intima?

Answer 2

It is the innermost layer close to the lumen, made of endothelium (simple squamous epithelium) resting on a basal lamina with a subendothelial layer of loose connective tissue and an internal elastic lamina.

Question 3

What is the composition and function of the tunica media?

Answer 3

It is composed of circular smooth muscle cells, elastic and reticular fibers. The smooth muscle cells regulate the diameter of the lumen, influencing blood pressure and flow.

Question 4

What are the characteristics of large elastic (conducting) arteries like the aorta?

Answer 4

They have a thick tunica media with fenestrated elastic lamina and circular smooth muscle. The tunica externa is underdeveloped.

Question 5

Why do major elastic arteries contain a large amount of elastic fibers?

Answer 5

Elastic fibers enable major arteries to stretch and accommodate the blood ejected from the heart during ventricular contraction.

Question 6

What happens to arteries in atherosclerosis?

Answer 6

The tunica intima thickens due to cholesterol deposits and smooth muscle proliferation, leading to decreased elasticity, aneurysms, and possible rupture.

Question 7

What is the structure of medium-sized muscular arteries?

Answer 7

Examples include the brachial, femoral, and renal arteries. They have a prominent internal elastic lamina, thick tunica media with smooth muscle, and a clear external elastic lamina.

Question 8

What is the function of medium-sized muscular arteries?

Answer 8

They distribute blood to different body parts and regulate blood flow through their muscular walls under autonomic nervous system control.

Question 9

What are the characteristics of arterioles?

Answer 9

Arterioles have a diameter greater than 0.1mm, with 1-5 layers of circular smooth muscle in the media, and a scant adventitia.

Question 10

What are metarterioles, and where are they located?

Answer 10

Metarterioles are intermediate between arterioles and capillaries, containing interrupted layers of smooth muscle cells with precapillary sphincters.

Question 11

What is the structure of capillaries?

Answer 11

Small, thin-walled blood vessels with a luminal diameter of 8-10μm, made of a single layer of endothelial cells on a basal lamina, with pericytes aiding in contraction.

Question 12

What are the different types of capillaries?

Answer 12

Continuous (tight junctions), Fenestrated (with or without diaphragm), and Sinusoids (large endothelial fenestrations).

Question 13

What are venules, and what is their function?

Answer 13

Venules are small veins that collect blood from capillaries. Their tunica media contains a few smooth muscle cells and fibroblasts, allowing phagocytic white blood cells to escape.

Question 14

What are the characteristics of medium-sized veins?

Answer 14

These veins have thinner walls than arteries, a thicker adventitia, and contain valves to prevent blood backflow.

Question 15

How do medium-sized arteries differ from medium-sized veins?

Answer 15

Arteries have thick walls and narrow lumens without valves, while veins have thin walls, wide lumens with valves, and thicker adventitia.

Question 16

What are the structural characteristics of veins compared to arteries?

Answer 16

Veins have thinner walls than arteries of the same diameter, a thick adventitia, and are adaptable to variations in volume and pressure, often containing valves.

Question 17

What are lymphatic capillaries, and what is their structure?

Answer 17

Small, thin-walled blind-end tubes with a larger diameter than blood capillaries, lacking pericytes, and having gaps between endothelial cells.

Question 18

How do medium-sized lymphatic vessels resemble veins, and what are their features?

Answer 18

They resemble veins but are thinner, with more bicuspid valves. They have a tunica intima lined by endothelial cells and a tunica media with smooth muscle.

Question 19

What are lymphatic ducts, and what is their structure?

Answer 19

The main ducts (thoracic and right lymphatic duct) formed by joining lymphatic vessels, containing smooth muscle in the media and connective tissue in the adventitia.