Histology of Heart and Blood Vessels

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Questions and Answers

What happens when cardiac muscle fibers are lost?

They are replaced by adipose tissue

They are replaced by new muscle fibers

They undergo cell division to regenerate

They are replaced by fibrous tissue (correct)

What is the function of the vasa vasorum?

To remove waste products from the blood vessels

To regulate blood pressure

To supply blood to the inner part of the blood vessels

To supply blood to the outer part of the blood vessels (correct)

What is the characteristic of the tunica media in large arteries like the aorta?

It has a single layer of elastic fibers

It consists of simple squamous endothelium

It has a fenestrated elastic membrane with 40-70 layers (correct)

It is rich in collagen fibers only

What is the type of epithelium lining the tunica intima?

Simple squamous epithelium Signup and view all the answers

What is the main function of the intercalated disc in cardiac muscle fibers?

To prevent separation of muscle cells during heart contraction Signup and view all the answers

What is the consequence of cardiac muscle growth?

It increases in size through hypertrophy Signup and view all the answers

What is the type of muscle present in the tunica media?

Smooth muscle Signup and view all the answers

What is the characteristic of the sarcoplasm in cardiac muscle fibers?

It is acidophilic and contains glycogen granules, mitochondria, and myofibrils Signup and view all the answers

What is the function of the transverse tubule (TT) in cardiac muscle fibers?

To send wide tubules into the myofibrils Signup and view all the answers

What is the characteristic of the Purkinje fibers?

They are modified cardiac muscle fibers forming part of the conducting system Signup and view all the answers

What is the outer layer of the heart composed of?

Simple squamous mesothelium and submesothelial layer of CT Signup and view all the answers

What is the characteristic of the cardiac muscle fibers under a light microscope?

They are short, cylindrical cells with oval, central, mono or binucleated nuclei Signup and view all the answers

What is the characteristic of the intima layer in a medium-sized vein?

Thin and does not contain internal elastic lamina Signup and view all the answers

What is the primary component of the media layer in a medium-sized artery?

Smooth muscle fibers Signup and view all the answers

Which type of blood vessel has a thicker adventitia layer?

Medium-sized vein Signup and view all the answers

What is the primary function of blood capillaries?

Conducting blood from arterioles to venules Signup and view all the answers

What is unique about the lumen of a medium-sized vein?

It is collapsed and usually contains blood after death Signup and view all the answers

What is the characteristic of vasa vasorum?

They are small blood vessels Signup and view all the answers

What is the main characteristic of fenestrated capillaries?

They have endothelium with pores closed by a thin diaphragm Signup and view all the answers

Where are sinusoids typically found?

In bone marrow, spleen, liver, and endocrine glands Signup and view all the answers

What is the function of capillaries?

To exchange gases and nutrients Signup and view all the answers

What is unique about the endothelium in sinusoids?

It is fenestrated without a diaphragm Signup and view all the answers

What is the role of macrophages in sinusoids?

To engulf foreign bodies Signup and view all the answers

What is the diameter range of sinusoids?

5-30 μm Signup and view all the answers

What is the primary function of A-V Shunts?

To regulate body temperature and blood flow Signup and view all the answers

Which of the following is a characteristic of large veins?

They contain only smooth muscles Signup and view all the answers

Where are Vasa Vasorum typically found?

In blood sinusoids Signup and view all the answers

What is a characteristic feature of blood sinusoids?

They have a larger diameter than blood capillaries Signup and view all the answers

What type of A-V Shunts can be found in the skin, ear pinna, and nail bed?

Complicated Signup and view all the answers

Study Notes

Heart Structure

The heart has three layers:
Inner layer = endocardium
Middle layer = myocardium (formed of cardiac muscle fibers that run in various directions)
Outer layer = epicardium (formed of simple squamous mesothelium and submesothelial layer of connective tissue containing coronary vessels)

Cardiac Muscle Fibers

Short, cylindrical cells in the heart wall
Involuntary
Cells are joined together by intercalated discs
Intercaled discs prevent separation of muscle cells during heart contraction
LM diameter: small (25 µm), branching and anastomosing, show cytoplasmic striation
Nuclei: oval, central, mono- or bi-nucleated
Sarcoplasm contains glycogen granules, mitochondria, myofibrils, and lipochrome pigments

Purkinje Fibers

Modified cardiac muscle fibers
Form part of conducting system
Larger diameter than cardiac muscle fibers

Blood Vessels

Types: arteries, veins, blood capillaries, blood sinusoids, arteriovenous shunts
Arteries: large elastic (aorta), medium-sized (muscular) arteries, arterioles
Veins: venules, medium-sized veins, large veins (inferior vena cava)

Blood Capillaries

Thin blood channels that conduct blood from terminal arterioles to venules (capillary beds)
Diameter: 8-10 μm
1 layer of endothelial cells resting on basement membrane
Types:
Continuous (somatic) capillary
Fenestrated capillary
Blood sinusoids

Blood Sinusoids

Dilated, irregular capillaries (5-30 μm)
Endothelium is fenestrated without diaphragms
Endothelium rests on reticular connective tissue (no basement membrane)
Macrophages extend between endothelial cells to engulf any foreign body
Sites: bone marrow, spleen, liver, endocrine glands

General Structure of Blood Vessels

Tunica intima: endothelial lining, subendothelial layer, internal elastic lamina
Tunica media: smooth muscle, elastin, collagenous and reticular fibers
Tunica adventitia: connective tissue, vasa vasorum (small blood vessels)

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Description

A comprehensive quiz on the histology of the heart and blood vessels, covering the inner, middle, and outer layers. Learn about the endocardium, myocardium, and epicardium, and understand their composition and functions.