Circulatory system Flashcards
Name and describe the 3 layers of the heart
- ) Endocardium: Innermost layer lining the lumen of the ventricles. Consists of a thin, flattened inner layer of endothelium (facing the blood) and supportive connective tissue, a middle myoelastic layer of smooth muscle and connective tissue, and a deep layer of connective tissue called the SUBENDOCARDIAL layer which merges with the myocardium.
- ) Myocardium: The middle and thickest layer. Consists mainly of cardiac muscle with fibers wound in a spiral fashion around each chamber. Thicker in the ventricles (particularly on left) than in the atria.
- ) Epicardium: Outer layer. Simple squamous mesothelium supported by a layer of loose connective tissue containing blood vessels and nerves. The epicardium corresponds to the VISCERAL LAYER OF THE PERICARDIUM.
What are the two components to the circulatory system?
- ) Blood vascular system (cardiovascular system)
2. ) Lymphatic vascular system
What do intercalated discs of cardiac muscle consist of?
They are junctional complexes consisting desmosomes, fascia adherens, and gap junctions.
What is the name for the deep endocardium layer and what does it contain?
Subendocardium: Contains NONCONTRACTILE, impulse conducting PURKINJE FIBERS.
What is the location and function of the cardiac skeleton?
It forms the interventricular and interatrial septae, surrounds all valves of the heart, and extends to the chordae tendineae.
It functions to:
- Anchor and support the heart valves (the valves themselves have an inner core of connective tissue which are surrounded by endothelium, which is continuous with the cardiac skeleton).
- Provides firm points of insertion for cardiac muscle (e.g. atrial and ventricular muscle).
- Helps coordinate the heartbeat by acting as electrical insulation between atria and ventricles.
Describe the location and histologic appearance of Purkinje fibers.
(9.7 Wilson)
Located in the subendocardial layer. They are larger AND paler than contractile muscle fibers. They also have less myofilaments and more glycogen (which is why they are larger and paler).
What are the three concentric layers (tunics) of the larger blood vessels?
- ) Tunica Intima (innermost layer): Contains INTERNAL ELASTIC LAMINA (composed of elastin) in arteries and large veins.
- ) Tunica Media (middle layer): Consists of concentric layers of helically arranged smooth muscle cells with elastic fibers, elastic lamellae, reticular fibers, and proteoglycans…ALL PRODUCED BY SMOOTH MUSCLE CELLS!
- ) Outer Adventitia (Tunica Externa): Consists of TYPE 1 COLLAGEN and elastic fibers.
Give characteristics of elastic arteries (aka _____ vessels)
Aka Conducting vessels: Provide a low resistance pathway for blood from the heart to medium-sized vessels.
- Elastic tissue allows expansion (systole) and contraction (diastole).
- Helps to maintain a SMOOTH BP CURVE.
- ) What is characteristic of the tunica media within muscular arteries (aka _______ vessels)?
- ) Why are they called this?
- ) What is their generalized function?
(9. 24 Wilson)
1. ) The media tends to be relatively thick because it has many layers of SMOOTH MUSCLE.
- ) aka DISTRIBUTING vessels –> They are called this because they distribute blood to various organs the body. They typically have names, e.g. coronary arteries, mesenteric arteries, cerebral arteries, etc.
- ) They control the amount of blood flow to organs by expanding and contracting in response to stimuli. Some role in maintaining BP as well.
Arterioles, aka ______ vessels. Describe composition and role.
Resistance vessels: Small vessels with ONE or TWO layers of smooth muscle in their media. They are the PRiMARY SITE OF VASCULAR RESISTANCE, thus, THEY MAINLY CONTROL BP!
Describe the vasa vasorum (aka ______)
Vasa vasorum, aka vessels of vessels: Micro-vessels supplying the adventitia of large blood vessels (e.g. vena cava, aorta, etc.) because these vessels are so large and thick that diffusion of nutrients to and from the lumen does not reach the outer layers of the vessel wall (adventitia, outer media). THEY NEED ADDITIONAL BLOOD SUPPLY.
Describe capillaries, aka _____ vessels.
Exchange vessels: Exchange metabolites by DIFFUSION to and from cells. They have very thin vessel walls and supply tissues with nutrients. Consist mainly of endothelial cells. Contain PERICYTES.
Describe the position of pericytes within capillaries
Sit just outside the endothelial cells and bulge OPPOSITE of the lumen.
Describe the function and appearance of PERICYTES.
- After tissue injuries, pericytes proliferate and differentiate to form smooth muscle and other cells in new vessels*
- Mesenchymal cells.
- Have long cytoplasmic processes partly surrounding the endothelial layer.
- Produce their own basal lamina.
- PRIMARY FUNCTION is contraction to facilitate flow of blood cells.
Describe the three types of capillaries.
- ) Continuous: Most common type. Found in muscle, connective tissue, nervous tissue. Basement membrane is continuous. Lots of tight junctions.
- ) Fenestrated: Found in kidneys, intestine, endocrine gland. Fenestrated to allow more materials to flow to and from the lumen.
- ) Discontinuous capillaries (SINUSOIDAL capillaries or sinusoids): Found in liver, spleen, bone marrow. Allows more the MOST MATERIAL EXCHANGE of all the capillary types.
- Basement membrane is discontinuous.
- Less tight junctions between the individual endothelial cells.
- Greatest capacity for exchange…so much so that cells can pass back and forth (e.g. macrophages).
- Greater DIAMETER than most capillaries.
