Cardiovascular Histology Flashcards
What is the primary function of the heart in the cardiovascular system?
The heart is responsible for pumping blood throughout the body.
Name the types of blood vessels in the cardiovascular system.
The types of blood vessels include arteries, arterioles, capillaries, veins, and venules.
What two aspects are shown at the bottom of the diagram in relation to blood vessels?
The lumen diameter (how wide the vessel is) and the thickness of the vessel walls.
What determines the structure and composition of arteries, arterioles, capillaries, and veins?
Their distance from the heart and the pressure they are exposed to.
What are the three layers of the heart called?
Endocardium, myocardium, and epicardium.
What are the three layers of blood vessels referred to as?
Tunica intima, tunica media, and tunica adventitia.
What is the innermost layer of the heart and blood vessels?
Tunica intima in blood vessels and endocardium in the heart.
What is the tunica media and what is it composed of in the heart and vessels?
The tunica media is the middle layer, composed of cardiac muscle in the heart and smooth muscle in the vessels.
What is the outermost layer of the heart and blood vessels?
Epicardium in the heart and tunica adventitia in blood vessels.
What is the endothelium and where is it located?
The endothelium is the innermost lining layer that is one cell thick and is continuous throughout the entire cardiovascular system.
How are the layers of the heart and blood vessels similar?
Both have layers that consist of similar components, though they are referred to differently (cardium for the heart, tunics for blood vessels).
What suffix do the layers of the heart have?
The layers of the heart have the suffix “cardium.”
What are the two components of the endocardium?
The endocardium consists of the endothelium (a one-cell-thick layer) and the subendothelium (a connective tissue layer).
What is the primary composition of the myocardium?
The myocardium is primarily composed of cardiac muscle.
What connective tissue structures subdivide cardiac muscle in the myocardium?
Endomysium, perimysium, and epimysium subdivide the cardiac muscle.
What is the epicardium and what does it contain?
The epicardium is the outer layer of the heart, mostly composed of connective tissue and contains blood vessels, collectively called vasa vasorum.
What is the function of the pericardial layer?
The pericardial layer is a sac that contains the heart and secretes fluid to allow the heart to contract in a frictionless environment.
Where do Purkinje fibers reside in the heart?
Purkinje fibers reside in the subendothelial layer of the endocardium.
How do Purkinje fibers differ from typical cardiac muscle cells?
Purkinje fibers are larger, lighter in color due to higher glycogen content, and have more gap junctions compared to typical cardiac muscle cells.
What is the conduction speed of Purkinje fibers compared to myocardial cells?
Purkinje fibers conduct impulses at about 3 to 4 meters per second, while myocardial cells conduct at about 0.5 meters per second.
Why is there an abundance of connective tissue between the atria and ventricles?
The connective tissue prevents out-of-order conduction of impulses, ensuring that the atria fill before the ventricles contract.
How does the connective tissue assist in the function of the heart?
It compresses the heart chambers during contraction to expel blood, supports heart valves, and provides structural integrity.
What are the primary types of blood vessels in the cardiovascular system?
The primary types of blood vessels include arteries, arterioles, capillaries, veins, and venules.
What are the two types of cardiac muscle found in the heart?
Cardiac muscle is found in the myocardium (heart muscle layer) and in the major veins (e.g., pulmonary vein, superior and inferior vena cava).
Why is there cardiac muscle present in the major veins?
To ensure synchrony of firing so that the beginning parts of the veins contract simultaneously with the heart muscle during blood expulsion.
What are the types of connective tissue associated with cardiac muscle?
The connective tissues include perimysium (around fascicles), endomysium (around individual muscle cells), and subendocardial connective tissue.
Why is there a high density of capillaries in the heart muscle?
To supply oxygen and nutrients necessary for continuous energy for contraction.
What structural feature distinguishes cardiac muscle cells from skeletal muscle cells?
Cardiac muscle cells have intercalated discs, which mark the ends of one cell and the beginning of another.
What is the purpose of the branching structure of cardiac muscle cells?
Branching increases connectivity between adjacent cells, allowing for synchronized contraction.
What are desmosomes?
Desmosomes are structural adhesions that provide mechanical support between adjacent cardiac muscle cells, helping them stay connected during contraction.
What role do gap junctions play in cardiac muscle?
Gap junctions facilitate the rapid transport of ions and allow for synchronous contraction of cardiac muscle cells.
What is the significance of mitochondria in cardiac muscle cells?
Mitochondria provide the necessary energy for muscle contraction, supporting the heart’s continuous activity.
What are beta-adrenergic receptors in cardiac muscle cells responsible for?
They facilitate increased contractility and heart rate when activated.
How do T-tubules and the sarcoplasmic reticulum function in cardiac muscle?
They form a dyad that helps convert electrical signals into calcium release, allowing for muscle contraction.
What is the main difference between triads in skeletal muscle and dyads in cardiac muscle?
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.
Why is synchronous contraction important in the heart?
To ensure all muscle cells within a chamber contract at nearly the same time for effective blood expulsion.
What are the three layers of blood vessels?
The three layers are the tunica intima, tunica media, and tunica adventitia.
What comprises the tunica intima?
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).
What is the function of the internal elastic lamina in blood vessels?
The internal elastic lamina serves as a boundary between the tunica intima and the tunica media, allowing for flexibility and support.
What is found in the tunica media?
The tunica media contains smooth muscle, collagen fibers, and elastic fibers.
How does the amount of collagen and elastic fibers in the tunica media vary?
The amounts of collagen and elastic fibers are dictated by the pressure the blood vessel is exposed to.
What does the wavy appearance in the tunica media indicate?
The wavy appearance is due to relaxed elastic fibers in the internal elastic lamina.
What is the tunica adventitia, and what is it composed of?
The tunica adventitia is the outermost layer of blood vessels, composed largely of connective tissue and elastic fibers.
What is the vaso vasorum?
The vaso vasorum is a network of small blood vessels that supply larger blood vessels with nutrients and oxygen.
How does the structure of a muscular artery differ from that of other arteries?
A muscular artery has fewer elastic fibers in the tunica media and a distinct boundary between the muscle layer and the tunica adventitia.
Why is the presence of elastic fibers important in blood vessels?
Elastic fibers provide the ability to stretch and recoil, helping to maintain blood pressure and facilitate blood flow.
What type of muscle is found in blood vessels?
Smooth muscle.
How do smooth muscle cells appear histologically?
They are spindle-shaped with blue nuclei and form concentric rings around the lumen of the blood vessel.
How do smooth muscle layers control the diameter of blood vessels?
When smooth muscle contracts, it decreases the diameter of the lumen; when it relaxes, it increases the diameter.
What is notable about the connective tissue in smooth muscle compared to cardiac and skeletal muscle?
Smooth muscle has less connective tissue and is not as highly organized.
What stimuli do smooth muscle cells respond to?
Smooth muscle responds to stretch, changes in pressure, hormones, and autonomic sympathetic input.
How do smooth muscle cells communicate with one another?
They communicate via gap junctions, allowing calcium to flow between adjacent cells for synchronized contraction.
Why doesn’t each smooth muscle cell require direct neural synapse for contraction?
Smooth muscle contraction can occur more slowly and synchronously through gap junctions, making individual nerve connections unnecessary.
What type of autonomic input do smooth muscle cells receive?
Smooth muscle receives sympathetic autonomic input but not parasympathetic input.
What happens to blood vessels during the fight-or-flight response?
Blood vessels supplying skeletal muscles dilate to increase blood flow, while blood vessels supplying skin and internal organs constrict.
What is the role of sympathetic input in blood vessel function?
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.
What are the primary purposes of arteries?
To conduct and distribute blood to the capillaries for exchange.
What are the three main types of arteries?
Elastic arteries, muscular arteries, and arterioles (including meta-arterioles).
What is the primary function of elastic arteries?
Elastic arteries are known as conducting arteries that handle the immediate blood flow from the heart.
Name three examples of elastic arteries.
The aorta, common carotids, and subclavian arteries.
What distinguishes the tunica media of elastic arteries?
It contains an abundance of elastic fibers (about 50/50 elastic to smooth muscle) to accommodate high pressure.
What is the role of elastic fibers in elastic arteries?
They allow the arteries to expand and contract, maintaining a constant flow of blood regardless of heart activity.
What are muscular arteries known for?
They are known as distributing arteries, which distribute blood to various regions of the body.
How do muscular arteries differ from elastic arteries in structure?
Muscular arteries have fewer elastic fibers and possess both an internal and external elastic lamina.
What happens to the distinct layers in smaller muscular arteries?
As arteries become smaller, the distinction of layers, including the external elastic lamina, becomes less defined.
What is the significance of arterioles in the circulatory system?
Arterioles regulate blood pressure and flow by constricting or relaxing, which influences total peripheral resistance.
What is the structure of arterioles?
Arterioles have a tunica intima and a tunica media that can range from one to five layers of smooth muscle.
What are meta-arterioles, and how do they function?
Meta-arterioles act as a bypass mechanism, allowing blood to either shunt directly to venules or perfuse into capillary beds based on tissue needs.
How do meta-arterioles differ from arterioles in structure?
Meta-arterioles have discontinuous smooth muscle, unlike the continuous layer found in true arterioles.
What is the relationship between arterioles and blood pressure regulation?
Constriction of many arterioles increases total peripheral resistance and blood pressure; relaxation decreases them.
In a capillary bed, what roles do arterioles and meta-arterioles play?
Arterioles supply blood, while meta-arterioles can direct blood flow to capillaries or bypass them based on the body’s needs.
What is the primary function of capillaries in the circulatory system?
To facilitate the diffusion of gases, nutrients, and waste with low pressure and slow blood flow.
What structural feature allows capillaries to maximize exchange surface area?
Capillaries are typically organized in beds, which are collections of many capillaries.
What is the diameter of capillaries, and why is it significant?
Capillaries have a diameter small enough to allow only one red blood cell to pass at a time, enhancing gas and nutrient exchange.
Describe the basic structure of a capillary.
Capillaries consist of a single layer of endothelial cells surrounded by a basement membrane.
What are pericytes, and what is their function?
Pericytes are cells surrounding capillaries that can differentiate into endothelial cells, fibroblasts, or smooth muscle cells as needed.
What are the three types of capillaries?
Continuous (tight), fenestrated, and discontinuous (sinusoidal) capillaries.
What characterizes continuous capillaries?
They have tight junctions between endothelial cells, forming a barrier that restricts passage between cells.
Where are fenestrated capillaries commonly found, and what is their structure?
Found in the kidneys, fenestrated capillaries have pores between endothelial cells but a continuous basement membrane.
Describe the structure and location of discontinuous (sinusoidal) capillaries.
Discontinuous capillaries have large openings and a discontinuous basement membrane, found in organs like the liver, allowing for the passage of large molecules.
What roles do intermediate and actin filaments play in endothelial cells?
They facilitate synchronous contraction between adjacent endothelial cells when responding to changes in the vascular environment.
How do endothelial cells respond to changes in blood pressure?
They can sense stretch and adapt, allowing for synchronized responses throughout the cardiovascular system.
What protective function do endothelial cells provide?
They form a barrier (like the blood-brain barrier) that selectively allows substances to pass while preventing unwanted material from crossing.
What vasoactive substances do endothelial cells secrete, and what are their effects?
They secrete nitric oxide (causes vasodilation) and endothelin (causes vasoconstriction), regulating vascular tone.
What is prostacyclin, and what is its role in the vascular system?
Prostaglandin secreted by endothelial cells that acts as an antiplatelet agent, preventing platelet aggregation under normal conditions.
How do endothelial cells respond to injury?
They secrete substances that promote inflammation, white blood cell migration, and formation of a platelet plug at the injury site.
What is angiogenesis, and what promotes it?
Angiogenesis is the formation of new capillaries, promoted by substances secreted by endothelial cells.
What are postcapillary venules, and how do they differ from capillaries?
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.
What role do postcapillary venules play in inflammation?
They allow for the migration of white blood cells (leukocytes) through diapedesis, facilitating the inflammatory response.
Describe the characteristics of muscular venules.
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.
How do veins differ structurally from arteries?
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.
Why do veins require valves, and how do these valves function?
Valves prevent backflow of blood, ensuring it moves towards the heart. They open when blood flows through and collapse to prevent reverse flow.
What are the three layers found in larger veins, and which is the thickest?
The three layers are tunica intima, tunica media, and tunica adventitia. The tunica adventitia is typically the thickest layer.
What is the function of the vasa vasorum in veins?
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.
How do the valves in veins help combat the effects of gravity?
Valves ensure that blood flows in one direction towards the heart, preventing pooling in the lower extremities due to gravity.
What happens when venous valves become incompetent?
Incompetent valves can lead to conditions like varicose veins, increased pressure, hemorrhaging, and potentially deep vein thrombosis.
What is varicose veins, and what causes it?
Varicose veins occur when valves in veins become incompetent, causing increased pressure that can lead to valve rupture and pooling of blood.
How does the structure of small to medium veins support their function?
Small to medium veins have collagen and elastic fibers in their valves, allowing them to respond appropriately to blood flow and recoil after opening.
What is diapedesis in the context of postcapillary venules?
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.
