Histo 1

Question 1

Describe the epicardium.

Answer 1

The epicardium is the visceral layer of the serous pericardium, consisting of a single layer of mesothelial cells supported by loose connective tissue.

Question 2

What is the composition of the valves of the heart?

Answer 2

The valves of the heart are composed of avascular dense fibrous connective tissue mainly made of collagen and elastic fibers, covered on both sides by endothelium.

Question 3

Define endocardium.

Answer 3

The endocardium consists of a thin layer of endothelium and supported connective tissue, along with a sub-endocardial layer containing smooth muscles and connective tissue that is continuous with the myocardium.

Question 4

How are cardiac muscle fibers held together and supported?

Answer 4

Cardiac muscle fibers are arranged into bundles held together and supported by connective tissue organized into ordinary (contractile) cardiomyocytes, endocrine cardiomyocytes, and cardiomyocytes of the conducting system.

Question 5

Describe the myocardium.

Answer 5

The myocardium is the middle and main layer of the heart wall, formed mainly of cardiac muscle fibers arranged spirally around each heart chamber, with branched interconnected muscle fibers by intercalated discs.

Question 6

What initiates the contraction of cardiac muscle fibers?

Answer 6

The contraction of cardiac muscle fibers is initiated by the spontaneous depolarization of pacemaker cells.

Question 7

What is the structure of cardiac myocytes in terms of nuclei and fibers?

Answer 7

Each cardiac muscle fiber is made up of cells called cardiac myocytes with a single central oval nucleus, forming long cylindrical fibers that branch and anastomose with neighboring fibers.

Question 8

How does the sarcoplasmic reticulum in cardiac muscle compare to that in skeletal muscle?

Answer 8

The sarcoplasmic reticulum in cardiac muscle is less in number and poorly developed compared to skeletal muscle, with wider and more numerous transverse tubules forming a Diad tubular system at the level of the Z-line.

Question 9

Describe the structure of cardiac muscle fibers in terms of glycogen and lipofuscin granules.

Answer 9

Glycogen granules are found between myofibrils, while lipofuscin granules increase with age, leading to brown atrophy of the heart.

Question 10

What are intercalated discs in cardiac muscle fibers and what components do they consist of?

Answer 10

Intercalated discs are specialized junctions between adjacent cardiac myocytes. They consist of desmosomes (transverse component) and gap junctions (lateral component).

Question 11

How do Purkinje fibers differ from typical cardiac muscle fibers in terms of structure and function?

Answer 11

Purkinje fibers are larger in diameter, have pale vacuolated cytoplasm rich in glycogen, lack typical intercalated discs, and terminate in the myocardium of the ventricles. They are more resistant to hypoxia and rapidly transmit contractile impulses via gap junctions.

Question 12

Define the role of the conducting system of the heart and its location.

Answer 12

The conducting system of the heart is responsible for the intrinsic regulation of heart rate and is located in the subendocardial layer of the endocardium.

Question 13

Describe the differences between atrial and ventricular muscle fibers in terms of T-tubules and secretory granules.

Answer 13

Atrial muscle fibers have smaller or absent T-tubules and electron-dense secretory granules, while ventricular muscle fibers have well-developed T-tubules with wide lumens and no secretory granules.

Question 14

How does the regeneration of cardiac muscle cells differ from other cell types?

Answer 14

Cardiac muscle cells cannot regenerate because they are a static cell population and lack satellite cells. Injured cardiac muscle fibers are replaced by fibrous tissue.

Question 15

Explain the components and functions of the vascular system.

Answer 15

The vascular system consists of the blood vascular system and the lymphatic vascular system, which carries fluid from tissue spaces to the blood. It includes the tunica intima, tunica media, and tunica adventitia with specific components in each layer like endothelium, smooth muscle fibers, and collagen fibers.

Question 16

Describe the general layers of a blood vessel wall.

Answer 16

The general layers include tunica intima, tunica media, and tunica adventitia.

Question 17

What is the composition of the tunica intima in blood vessels?

Answer 17

The tunica intima consists of endothelium, subendothelium, and internal elastic lamina.

Question 18

How does the tunica media of blood vessels function?

Answer 18

The tunica media contains smooth muscle fibers that regulate blood flow through contraction and produce extracellular components.

Question 19

Define tunica adventitia in blood vessels.

Answer 19

Tunica adventitia is the outermost layer of blood vessels, consisting of connective tissue like collagen and elastic fibers.

Question 20

Describe the role of vasa vasorum in blood vessels.

Answer 20

Vasa vasorum are small blood vessels found in the tunica adventitia of large vessels, supplying nutrients to the vessel walls.

Question 21

What is the structure of smooth muscle fibers?

Answer 21

Smooth muscle fibers are non-striated, spindle-shaped cells with a single central nucleus and arranged in bundles.

Question 22

How does regeneration occur in smooth muscle fibers?

Answer 22

Regeneration in smooth muscle fibers happens through the division of existing fibers and differentiation of pericytes.

Question 23

Differentiate between smooth muscle and cardiac muscle fibers.

Answer 23

Smooth muscle fibers are non-striated, have a single central nucleus, and repair through pericytes, while cardiac muscle fibers are striated, branched, and lack regenerative capacity.

Question 24

Describe the structure of the intima in large (elastic) arteries.

Answer 24

The intima in large (elastic) arteries consists of endothelium (simple squamous epithelium) and subendothelium containing smooth muscle fibers, elastic fibers, and collagen fibers.

Question 25

What is the main difference in smooth muscle and elastic fibers between large (elastic) arteries and medium (muscular) arteries?

Answer 25

Large arteries have more smooth muscle fibers and less elastic fibers compared to medium arteries.

Question 26

Define metarterioles.

Answer 26

Metarterioles are the terminal portions of arterioles that drain blood into the capillaries.

Question 27

How are atherosclerotic lesions characterized?

Answer 27

Atherosclerotic lesions are characterized by focal thickening of the intima, proliferation of smooth muscle cells, increased deposition of extracellular connective tissue elements and lipoprotein in the sub-endothelial layer.

Question 28

Describe the structure of the intima in small veins (venules).

Answer 28

The intima in small veins (venules) consists of endothelium (simple squamous epithelium) and a very thin subendothelium, with an absent internal elastic lamina (IEL).

Question 29

What is the function of precapillary sphincters formed by the smooth muscle of metarterioles?

Answer 29

Precapillary sphincters control blood flow to capillaries.

Question 30

Do large muscular arteries have a thick or thin tunica adventitia?

Answer 30

Large muscular arteries have a thin tunica adventitia.

Question 31

How does the structure of the media differ between large (elastic) arteries and medium (muscular) arteries?

Answer 31

Large arteries have 40-70 laminae of fenestrated circular elastic membranes of elastin in the media, while medium arteries have 4-40 layers of circularly arranged smooth muscle.

Question 32

Define arterioles.

Answer 32

Arterioles are small arteries that have increased smooth muscle tone in their media, which can lead to hypertension.

Question 33

Describe the structure of the tunica media in medium (muscular) arteries.

Answer 33

The tunica media in medium arteries is thick and contains smooth muscle, elastic fibers, and fat droplets, with a clear internal elastic lamina (IEL).

Question 34

Describe the structure of the tunica intima in a medium-sized artery.

Answer 34

The tunica intima in a medium-sized artery consists of endothelium and a subendothelium that is thin and poor in elastic fibers, with no internal elastic lamina (IEL).

Question 35

What are the components of the tunica media in a medium-sized vein?

Answer 35

The tunica media in a medium-sized vein is thin and consists of a few smooth muscle layers, few elastic and reticular fibers, and lacks an external elastic lamina (EEL).

Question 36

Define the adventitia in medium-sized veins.

Answer 36

The adventitia in medium-sized veins forms the main thickness of the wall, is rich in collagen fibers, and contains few elastic fibers. Valves are usually present.

Question 37

How do medium-sized arteries and veins differ in terms of wall thickness and lumen size?

Answer 37

Medium-sized arteries have thick walls and narrow, rounded lumens, while medium-sized veins have thin walls and wide lumens.

Question 38

Describe the differences in the structure of the tunica intima between a large elastic artery (Aorta) and a large vein (IV).

Answer 38

The tunica intima in the aorta is thicker, has a well-developed internal elastic lamina (IEL), and lacks valves, while in the IVC it is thinner, lacks an IEL, and has prominent valves.

Question 39

What is the role of valves in large veins like the inferior vena cava (IVC)?

Answer 39

Valves in large veins like the IVC prevent retrograde movement of blood by gravity, mainly found in veins of lower limbs.

Question 40

Describe the medical importance of cardiovascular endothelial cells.

Answer 40

Cardiovascular endothelial cells act as a selective permeable barrier, are anti-thrombogenic, anti-inflammatory, regulate vascular tone, and promote vessel formation and growth.

Question 41

How does damage to the endothelium contribute to thrombus formation?

Answer 41

Damage to the endothelium, such as by atherosclerotic lesions, can lead to uncovered subendothelial connective tissue, inducing platelet aggregation, thrombus formation, and obstruction of blood flow.

Question 42

Describe the structure and function of II-A/V Anastomosis (Shunt) in the body.

Answer 42

II-A/V Anastomosis, found in exposed body parts and certain organs, consists of direct connections between arterioles and venules without passing through capillaries. It helps regulate body temperature, blood flow in genital organs, and blood flow to organs during digestion, absorption, and secretion.

Question 43

Define the mechanism of action of A-V anastomoses (shunts) in blood circulation.

Answer 43

A-V anastomoses regulate blood flow by allowing blood to pass through capillary beds when the precapillary sphincter is relaxed, and directing a large amount of blood through the A/V shunt when the sphincter is closed, resulting in rapid circulation.

Question 44

How do different types of blood capillaries (continuous, fenestrated, sinusoidal) differ in structure and function?

Answer 44

Continuous capillaries have tight junctions and no pores, fenestrated capillaries have pores for increased permeability, and sinusoidal capillaries have wide gaps between cells. They vary in diameter, endothelium type, presence of pericytes, and sites in the body.

Question 45

Describe the differences between blood capillaries and lymphatic capillaries in terms of beginning, structure, and function.

Answer 45

Blood capillaries start from small arterioles, have smaller and less permeable lumens, and exchange materials with tissues. Lymphatic capillaries begin with blind ends, are more permeable, and remove lymph and large molecules like fat droplets and bacteria from interstitial spaces.

Question 46

What is the role of pericytes in blood and lymphatic capillaries?

Answer 46

Pericytes surround endothelium, regulate blood flow, and can differentiate into various cell types. In lymphatic capillaries, they help remove large molecules and regulate lymph flow.