Cardiovascular Histology

Question 1

What is the primary function of the heart in the cardiovascular system?

Answer 1

The heart is responsible for pumping blood throughout the body.

Question 2

Name the types of blood vessels in the cardiovascular system.

Answer 2

The types of blood vessels include arteries, arterioles, capillaries, veins, and venules.

Question 3

What two aspects are shown at the bottom of the diagram in relation to blood vessels?

Answer 3

The lumen diameter (how wide the vessel is) and the thickness of the vessel walls.

Question 4

What determines the structure and composition of arteries, arterioles, capillaries, and veins?

Answer 4

Their distance from the heart and the pressure they are exposed to.

Question 5

What are the three layers of the heart called?

Answer 5

Endocardium, myocardium, and epicardium.

Question 6

What are the three layers of blood vessels referred to as?

Answer 6

Tunica intima, tunica media, and tunica adventitia.

Question 7

What is the innermost layer of the heart and blood vessels?

Answer 7

Tunica intima in blood vessels and endocardium in the heart.

Question 8

What is the tunica media and what is it composed of in the heart and vessels?

Answer 8

The tunica media is the middle layer, composed of cardiac muscle in the heart and smooth muscle in the vessels.

Question 9

What is the outermost layer of the heart and blood vessels?

Answer 9

Epicardium in the heart and tunica adventitia in blood vessels.

Question 10

What is the endothelium and where is it located?

Answer 10

The endothelium is the innermost lining layer that is one cell thick and is continuous throughout the entire cardiovascular system.

Question 11

How are the layers of the heart and blood vessels similar?

Answer 11

Both have layers that consist of similar components, though they are referred to differently (cardium for the heart, tunics for blood vessels).

Question 12

What suffix do the layers of the heart have?

Answer 12

The layers of the heart have the suffix “cardium.”

Question 13

What are the two components of the endocardium?

Answer 13

The endocardium consists of the endothelium (a one-cell-thick layer) and the subendothelium (a connective tissue layer).

Question 14

What is the primary composition of the myocardium?

Answer 14

The myocardium is primarily composed of cardiac muscle.

Question 15

What connective tissue structures subdivide cardiac muscle in the myocardium?

Answer 15

Endomysium, perimysium, and epimysium subdivide the cardiac muscle.

Question 16

What is the epicardium and what does it contain?

Answer 16

The epicardium is the outer layer of the heart, mostly composed of connective tissue and contains blood vessels, collectively called vasa vasorum.

Question 17

What is the function of the pericardial layer?

Answer 17

The pericardial layer is a sac that contains the heart and secretes fluid to allow the heart to contract in a frictionless environment.

Question 18

Where do Purkinje fibers reside in the heart?

Answer 18

Purkinje fibers reside in the subendothelial layer of the endocardium.

Question 19

How do Purkinje fibers differ from typical cardiac muscle cells?

Answer 19

Purkinje fibers are larger, lighter in color due to higher glycogen content, and have more gap junctions compared to typical cardiac muscle cells.

Question 20

What is the conduction speed of Purkinje fibers compared to myocardial cells?

Answer 20

Purkinje fibers conduct impulses at about 3 to 4 meters per second, while myocardial cells conduct at about 0.5 meters per second.

Question 21

Why is there an abundance of connective tissue between the atria and ventricles?

Answer 21

The connective tissue prevents out-of-order conduction of impulses, ensuring that the atria fill before the ventricles contract.

Question 22

How does the connective tissue assist in the function of the heart?

Answer 22

It compresses the heart chambers during contraction to expel blood, supports heart valves, and provides structural integrity.

Question 23

What are the primary types of blood vessels in the cardiovascular system?

Answer 23

The primary types of blood vessels include arteries, arterioles, capillaries, veins, and venules.

Question 24

What are the two types of cardiac muscle found in the heart?

Answer 24

Cardiac muscle is found in the myocardium (heart muscle layer) and in the major veins (e.g., pulmonary vein, superior and inferior vena cava).

Question 25

Why is there cardiac muscle present in the major veins?

Answer 25

To ensure synchrony of firing so that the beginning parts of the veins contract simultaneously with the heart muscle during blood expulsion.

Question 26

What are the types of connective tissue associated with cardiac muscle?

Answer 26

The connective tissues include perimysium (around fascicles), endomysium (around individual muscle cells), and subendocardial connective tissue.

Question 27

Why is there a high density of capillaries in the heart muscle?

Answer 27

To supply oxygen and nutrients necessary for continuous energy for contraction.

Question 28

What structural feature distinguishes cardiac muscle cells from skeletal muscle cells?

Answer 28

Cardiac muscle cells have intercalated discs, which mark the ends of one cell and the beginning of another.

Question 29

What is the purpose of the branching structure of cardiac muscle cells?

Answer 29

Branching increases connectivity between adjacent cells, allowing for synchronized contraction.

Question 30

What are desmosomes?

Answer 30

Desmosomes are structural adhesions that provide mechanical support between adjacent cardiac muscle cells, helping them stay connected during contraction.

Question 31

What role do gap junctions play in cardiac muscle?

Answer 31

Gap junctions facilitate the rapid transport of ions and allow for synchronous contraction of cardiac muscle cells.

Question 32

What is the significance of mitochondria in cardiac muscle cells?

Answer 32

Mitochondria provide the necessary energy for muscle contraction, supporting the heart’s continuous activity.

Question 33

What are beta-adrenergic receptors in cardiac muscle cells responsible for?

Answer 33

They facilitate increased contractility and heart rate when activated.

Question 34

How do T-tubules and the sarcoplasmic reticulum function in cardiac muscle?

Answer 34

They form a dyad that helps convert electrical signals into calcium release, allowing for muscle contraction.

Question 35

What is the main difference between triads in skeletal muscle and dyads in cardiac muscle?

Answer 35

Cardiac muscle has dyads (one T-tubule and one sarcoplasmic reticulum) rather than triads (two sarcoplasmic reticula and one T-tubule) found in skeletal muscle.

Question 36

Why is synchronous contraction important in the heart?

Answer 36

To ensure all muscle cells within a chamber contract at nearly the same time for effective blood expulsion.

Question 37

What are the three layers of blood vessels?

Answer 37

The three layers are the tunica intima, tunica media, and tunica adventitia.

Question 38

What comprises the tunica intima?

Answer 38

The tunica intima consists of an endothelial layer (one cell thick), a subendothelial layer of connective tissue, and the internal elastic lamina (made of elastic fibers).

Question 39

What is the function of the internal elastic lamina in blood vessels?

Answer 39

The internal elastic lamina serves as a boundary between the tunica intima and the tunica media, allowing for flexibility and support.

Question 40

What is found in the tunica media?

Answer 40

The tunica media contains smooth muscle, collagen fibers, and elastic fibers.

Question 41

How does the amount of collagen and elastic fibers in the tunica media vary?

Answer 41

The amounts of collagen and elastic fibers are dictated by the pressure the blood vessel is exposed to.

Question 42

What does the wavy appearance in the tunica media indicate?

Answer 42

The wavy appearance is due to relaxed elastic fibers in the internal elastic lamina.

Question 43

What is the tunica adventitia, and what is it composed of?

Answer 43

The tunica adventitia is the outermost layer of blood vessels, composed largely of connective tissue and elastic fibers.

Question 44

What is the vaso vasorum?

Answer 44

The vaso vasorum is a network of small blood vessels that supply larger blood vessels with nutrients and oxygen.

Question 45

How does the structure of a muscular artery differ from that of other arteries?

Answer 45

A muscular artery has fewer elastic fibers in the tunica media and a distinct boundary between the muscle layer and the tunica adventitia.

Question 46

Why is the presence of elastic fibers important in blood vessels?

Answer 46

Elastic fibers provide the ability to stretch and recoil, helping to maintain blood pressure and facilitate blood flow.

Question 47

What type of muscle is found in blood vessels?

Answer 47

Smooth muscle.

Question 48

How do smooth muscle cells appear histologically?

Answer 48

They are spindle-shaped with blue nuclei and form concentric rings around the lumen of the blood vessel.

Question 49

How do smooth muscle layers control the diameter of blood vessels?

Answer 49

When smooth muscle contracts, it decreases the diameter of the lumen; when it relaxes, it increases the diameter.

Question 50

What is notable about the connective tissue in smooth muscle compared to cardiac and skeletal muscle?

Answer 50

Smooth muscle has less connective tissue and is not as highly organized.

Question 51

What stimuli do smooth muscle cells respond to?

Answer 51

Smooth muscle responds to stretch, changes in pressure, hormones, and autonomic sympathetic input.

Question 52

How do smooth muscle cells communicate with one another?

Answer 52

They communicate via gap junctions, allowing calcium to flow between adjacent cells for synchronized contraction.

Question 53

Why doesn’t each smooth muscle cell require direct neural synapse for contraction?

Answer 53

Smooth muscle contraction can occur more slowly and synchronously through gap junctions, making individual nerve connections unnecessary.

Question 54

What type of autonomic input do smooth muscle cells receive?

Answer 54

Smooth muscle receives sympathetic autonomic input but not parasympathetic input.

Question 55

What happens to blood vessels during the fight-or-flight response?

Answer 55

Blood vessels supplying skeletal muscles dilate to increase blood flow, while blood vessels supplying skin and internal organs constrict.

Question 56

What is the role of sympathetic input in blood vessel function?

Answer 56

Sympathetic input can provide different messages to various regions of blood vessels based on the body’s needs, such as increased blood flow to muscles during stress or danger.

Question 57

What are the primary purposes of arteries?

Answer 57

To conduct and distribute blood to the capillaries for exchange.

Question 58

What are the three main types of arteries?

Answer 58

Elastic arteries, muscular arteries, and arterioles (including meta-arterioles).

Question 59

What is the primary function of elastic arteries?

Answer 59

Elastic arteries are known as conducting arteries that handle the immediate blood flow from the heart.

Question 60

Name three examples of elastic arteries.

Answer 60

The aorta, common carotids, and subclavian arteries.

Question 61

What distinguishes the tunica media of elastic arteries?

Answer 61

It contains an abundance of elastic fibers (about 50/50 elastic to smooth muscle) to accommodate high pressure.

Question 62

What is the role of elastic fibers in elastic arteries?

Answer 62

They allow the arteries to expand and contract, maintaining a constant flow of blood regardless of heart activity.

Question 63

What are muscular arteries known for?

Answer 63

They are known as distributing arteries, which distribute blood to various regions of the body.

Question 64

How do muscular arteries differ from elastic arteries in structure?

Answer 64

Muscular arteries have fewer elastic fibers and possess both an internal and external elastic lamina.

Question 65

What happens to the distinct layers in smaller muscular arteries?

Answer 65

As arteries become smaller, the distinction of layers, including the external elastic lamina, becomes less defined.

Question 66

What is the significance of arterioles in the circulatory system?

Answer 66

Arterioles regulate blood pressure and flow by constricting or relaxing, which influences total peripheral resistance.

Question 67

What is the structure of arterioles?

Answer 67

Arterioles have a tunica intima and a tunica media that can range from one to five layers of smooth muscle.

Question 68

What are meta-arterioles, and how do they function?

Answer 68

Meta-arterioles act as a bypass mechanism, allowing blood to either shunt directly to venules or perfuse into capillary beds based on tissue needs.

Question 69

How do meta-arterioles differ from arterioles in structure?

Answer 69

Meta-arterioles have discontinuous smooth muscle, unlike the continuous layer found in true arterioles.

Question 70

What is the relationship between arterioles and blood pressure regulation?

Answer 70

Constriction of many arterioles increases total peripheral resistance and blood pressure; relaxation decreases them.

Question 71

In a capillary bed, what roles do arterioles and meta-arterioles play?

Answer 71

Arterioles supply blood, while meta-arterioles can direct blood flow to capillaries or bypass them based on the body’s needs.

Question 72

What is the primary function of capillaries in the circulatory system?

Answer 72

To facilitate the diffusion of gases, nutrients, and waste with low pressure and slow blood flow.

Question 73

What structural feature allows capillaries to maximize exchange surface area?

Answer 73

Capillaries are typically organized in beds, which are collections of many capillaries.

Question 74

What is the diameter of capillaries, and why is it significant?

Answer 74

Capillaries have a diameter small enough to allow only one red blood cell to pass at a time, enhancing gas and nutrient exchange.

Question 75

Describe the basic structure of a capillary.

Answer 75

Capillaries consist of a single layer of endothelial cells surrounded by a basement membrane.

Question 76

What are pericytes, and what is their function?

Answer 76

Pericytes are cells surrounding capillaries that can differentiate into endothelial cells, fibroblasts, or smooth muscle cells as needed.

Question 77

What are the three types of capillaries?

Answer 77

Continuous (tight), fenestrated, and discontinuous (sinusoidal) capillaries.

Question 78

What characterizes continuous capillaries?

Answer 78

They have tight junctions between endothelial cells, forming a barrier that restricts passage between cells.

Question 79

Where are fenestrated capillaries commonly found, and what is their structure?

Answer 79

Found in the kidneys, fenestrated capillaries have pores between endothelial cells but a continuous basement membrane.

Question 80

Describe the structure and location of discontinuous (sinusoidal) capillaries.

Answer 80

Discontinuous capillaries have large openings and a discontinuous basement membrane, found in organs like the liver, allowing for the passage of large molecules.

Question 81

What roles do intermediate and actin filaments play in endothelial cells?

Answer 81

They facilitate synchronous contraction between adjacent endothelial cells when responding to changes in the vascular environment.

Question 82

How do endothelial cells respond to changes in blood pressure?

Answer 82

They can sense stretch and adapt, allowing for synchronized responses throughout the cardiovascular system.

Question 83

What protective function do endothelial cells provide?

Answer 83

They form a barrier (like the blood-brain barrier) that selectively allows substances to pass while preventing unwanted material from crossing.

Question 84

What vasoactive substances do endothelial cells secrete, and what are their effects?

Answer 84

They secrete nitric oxide (causes vasodilation) and endothelin (causes vasoconstriction), regulating vascular tone.

Question 85

What is prostacyclin, and what is its role in the vascular system?

Answer 85

Prostaglandin secreted by endothelial cells that acts as an antiplatelet agent, preventing platelet aggregation under normal conditions.

Question 86

How do endothelial cells respond to injury?

Answer 86

They secrete substances that promote inflammation, white blood cell migration, and formation of a platelet plug at the injury site.

Question 87

What is angiogenesis, and what promotes it?

Answer 87

Angiogenesis is the formation of new capillaries, promoted by substances secreted by endothelial cells.

Question 88

What are postcapillary venules, and how do they differ from capillaries?

Answer 88

Postcapillary venules have an endothelial cell lining and a basement membrane like capillaries, but their endothelial cells can be discontinuous and leaky, allowing for easy fluid exchange.

Question 89

What role do postcapillary venules play in inflammation?

Answer 89

They allow for the migration of white blood cells (leukocytes) through diapedesis, facilitating the inflammatory response.

Question 90

Describe the characteristics of muscular venules.

Answer 90

Muscular venules have a larger lumen and some smooth muscle presence, allowing for vessel constriction to promote blood flow, but they do not have a continuous smooth muscle layer like arterioles.

Question 91

How do veins differ structurally from arteries?

Answer 91

Veins have thinner walls, more flexibility, and may appear misshapen compared to the more robust, circular structure of arteries, due to lower pressure in the venous system.

Question 92

Why do veins require valves, and how do these valves function?

Answer 92

Valves prevent backflow of blood, ensuring it moves towards the heart. They open when blood flows through and collapse to prevent reverse flow.

Question 93

What are the three layers found in larger veins, and which is the thickest?

Answer 93

The three layers are tunica intima, tunica media, and tunica adventitia. The tunica adventitia is typically the thickest layer.

Question 94

What is the function of the vasa vasorum in veins?

Answer 94

The vasa vasorum are small blood vessels that supply nutrients to the walls of larger veins, as the blood inside does not provide enough oxygen.

Question 95

How do the valves in veins help combat the effects of gravity?

Answer 95

Valves ensure that blood flows in one direction towards the heart, preventing pooling in the lower extremities due to gravity.

Question 96

What happens when venous valves become incompetent?

Answer 96

Incompetent valves can lead to conditions like varicose veins, increased pressure, hemorrhaging, and potentially deep vein thrombosis.

Question 97

What is varicose veins, and what causes it?

Answer 97

Varicose veins occur when valves in veins become incompetent, causing increased pressure that can lead to valve rupture and pooling of blood.

Question 98

How does the structure of small to medium veins support their function?

Answer 98

Small to medium veins have collagen and elastic fibers in their valves, allowing them to respond appropriately to blood flow and recoil after opening.

Question 99

What is diapedesis in the context of postcapillary venules?

Answer 99

Diapedesis is the process by which white blood cells migrate out of the bloodstream and into surrounding tissue, facilitated by the leaky nature of postcapillary venules.