The Cardiovascular System Flashcards
What two parts of the body make up the cardiovascular system? What makes up the circulatory system?
“Cardiovascular” refers to the heart and the blood vessels. “Circulatory” refers to these organs in addition to the blood as well as the lymphatic vessels.
What is the anatomical position of the heart? Describe what other features can be found here…
The heart is found between the lungs, within the mediastinum, tilting toward the left side of the body. The apex or lowermost portion of the heart is found lying just above the diaphragm.
The mediastinum also includes the esophagus, trachea, aorta, etc.
What surrounds the heart and how does this feature contribute to the heart’s function?
The heart is surrounded by a fibrous pericardial sac that enables the heart to have room for expansion while simultaneously preventing excess expansion. The sac secretes a lubricating substance called pericardial fluid which aids to minimize heart beat friction against the thoracic wall.
Describe the organization of the heart. Name the regions, divisions, and valves.
The two upper chambers are the right and left atrium separated from one another by the interatrial septum. The two lower chambers are the right and left ventricles, which are separated by the interventricular septum.
Between the right atrium and the right ventricle is the triscuspid valve - named for its consisting of three flaps or cusps. Between the right ventricle and the pulmonary artery is the pulmonary valve - which prevents backflow.
Between the left atrium and left ventricle is the bicuspid valve - named for its consisting of two flaps or cusps. Between the left ventricle and the aorta is the aortic valve which serves to prevent backflow
Pulmonary veins bring blood to the left atrium.
The vena cava (superior and inferior) bring blood into the right atrium.
Describe the direction of blood flow on the right side of the heart.
Blood flows into the right atrium through the superior vena cava.
The AV valve between the right atrium and ventricle is known as the tricuspid valve.
The right ventricle pumps blood into the pulmonary trunk, to the lungs.
The pulmonary valve regulates one-way blood flow out of the pulmonary trunk.
Describe the direction of blood flow on the left side of the heart.
The pulmonary veins bring blood into the left atrium.
The AV valve between the left atrium and ventricle is known as the bicuspid valve.
The left ventricle pumps blood into the aorta on its way to the body.
The aortic valve regulates one-way blood flow out of the aorta.
What layer of the heart is the most superficial? What cell type(s) is it made up of? Where is this layer the thickest?
Epicardium
Simple Squamous Epithelium aka Mesothelium overlying a layer of connective tissue and sometimes a thick deposit of adipose tissue.
*Various thickness
Thickest in the vicinity of the coronary sulcus, anterior interventricular sulcus, and posterior interventricular sulcus - the fat cushions the arteries and nerves running through the sulci.
What layer of the heart is the thickest? What cell types(s) is it made up of? What is this layer responsible for?
Myocardium
Composed of Cardiac Muscle Cells called Cardiocytes and Cardiomyocytes arranged in fascicles
Responsible for the rhythmic muscular contractions of the heart.
What layer of the heart is innermost? What cell type(s) is it made up of? What special structure is located here?
Endocardium
Similar histologically to the epicardium - simple squamous epithelium overlying a thin layer of areolar tissue (subendocardial layer).
contains nervelike “Purkinje fibers”
Describe the function and anatomy of the myocardial vortex.
Myocardial muscle fascicles are coiled around the heart in a spiraling pattern toward the apex - resulting in a twisting muscle contraction which is more effective for pumping blood.
Cardiocytes lack parallel orientation but rather are found in a variety of orientations.
Describe the cardiac skeleton.
a dense fibrous connective tissue forming the superior portion of the interventricular septum - separating the pathway of electrical signals into a specific order.
anuli fibrosi – encricle the bases of the aorta and pulmonary trunk
trigonum fibrosum – anchors valve cusps as patches
Describe the cells and orientation of cells that make up cardiac muscle.
Cardiocytes meet end to end at intercalated discs - featuring interdigitating folds that enhance surface area of cell-cell contact; fasciae adherentes and desmosomes that link cells together as well as gap junctions which allow for electrical communication between cells.
What is the function of specialized cardiocytes that generate and conduct electrical signals?
The cells define the “pacemaker” and the “cardiac conduction system” that coordinate heart movement.
Discuss the differences between the SA Node and the AV Node.
sinoatrial (SA) node - a small patch of cells just below the epicardium - located near the junction of the superior vena cava and the right atrium. this node spontaneously depolarizes and initiates cell - cell electrical stimulation resulting in atrial contraction.
atrioventrivular (AV) node - a small patch of cells just below the epicardium - located low in the right atrial wall above the interventricular spetum, close to the right AV valve. the route by which electrical signals of the SA node reach the ventricles (0.05 m/s, slowing down ventricular contraction to ensure the ventricles are completely full before contraction).
What is the function of the atrioventricular bundle or “bundle of His”?
a cord of cardiomyocytes arising in the AV sode running into the interventricular septum lying just below the endocardium to ensure rapid stimulation of the ventricular myocardium.
beginning in a solid bundle, it splits left right into branches giving rise to purkinje fibers.
What role do purkinje fibers play in electrical conduction?
located at the lower end of the septum, branches of the atrioventricular bundle give rise to these fine nerve-like extensions
these fibers conduct signals to the apex of the heart and upward in the ventricular walls.
as a result contraction starts in the apex of the heart, driving blood upward toward the pulmonary and aortic valves.
*fatter, more vacuolated than cardiomyocytes
What is the coronary sulcus?
a region between the atrium and ventricle that is filled with fat.
What are blood vessels?
tubular, muscular organs for the transport and distribution of blood.
What is the difference between the pulmonary and systemic circuit(s)?
Pulmonary - conducts blood from the heart to the lungs and back - only serving O2 and CO2 exchange
Systemic - conducts blood from the heart to all parts of the body and back again.
What are the three main classes of blood vessels? Describe the major differences.
Arteries, Veins, Capillaries
Arteries: Efferent - conduct blood away from the heart, subject to a great stress of blood pressure generated by the heart beat = most muscular vessel type resulting in circular cross sections where the tissue is strong. Smallest arteries = arterioles.
Veins: Afferent - conduct blood toward the heart, not as subject to blood pressure, thinner walls than arteries resulting in a collapsed shape when cross sectioned. Smallest veins = venules.
Capillaries: microscopic vessels that connect arteries and veins, not muscular at all.
What are the three walls that make up a blood vessel?
Tunica intima, Tunica media, Tunica adventitia
What layer of the blood vessels is continuous with the endocardium? What else is characteristic of this layer?
Tunica intima
a single layer of squamous endothelial cells with sparse areolar tissues and some vessels having fenestrated elastic lamina.
What layer of the blood vessels is consistent with smooth muscle?
Tunica media
a thick middle layer of smooth muscle, elastic and collagenous fibers sometimes with an external elastic lamina.
What layer of the blood vessels is consistent with loose connective tissue?
Tunica adventitia
the outermost layer of the vessel wall, a covering of loose connective tissue often blending with surrounding adventitia of other organs.
How do medium and large arteries adequately meet nutritional, oxidative and waste-removal needs?
Smaller vessels integrate into the adventitia of larger vessels, branching into capillaries that supply the tissues of larger vessels = vasa vasorum
A network of small vessels serving the larger one is called….
Vasa vasorum - responsible for nourishing the outer 2/3 of large vessel walls/
… regulate vessel diameter.
Sympathetic vasomotor nerves
A state of partial constriction of the blood vessel wall is called…
vasomotor tone
Name the three classes of arteries.
Small, Medium, Large
What are some examples of a large artery?
pulmonary trunk, pulmonary arteries, aorta, renal arteries, common iliac arteries
Describe the layers of a large artery.
- thick tunica intima
- internal elastic lamina - elastic tissue with holes - a single sheet between the tunica intima and tunica media
- thick tunica media - 40 - 70 layers of fenestrated membranes with smooth muscle between each membrane
- external elastic lamina between the tunica media and tunica adventitia
- thin tunica aventitia with a somewhat prominent vasa vasorum
*fenestrated - holes allowing for nerves and muscle cells, and vasa vasorum to pass through the layers of tunica media
Describe the layers of a medium artery.
- thin tunica intima
- thick, more prominent internal elastic lamina
- 3 - 40 layers of tunica media with NO fenestrated elastic sheets
- prominent external elastic lamina
- large tunica adventitia relative to the tunica media
Describe the layers of a small artery.
- internal elastic lamina in largest small arteries
- 1 - 5 layers of smooth muscle in tunica media
- may be small enough that a single muscle cell wraps entirely around the vessel’s diameter.
- no external elastic lamina
- scanty tunica adventitia
What are metarterioles?
Directly supply capillary beds and offer a route to bypass capillaries - having no tunica media
- have a single myocyte called the precapillary sphincter where a capillary arises from metarteriole. where if open blood flows into capillaries and if closed blood will bypass the capilaries and flow into a throughfare channel onto a venule.
What is distinctive about a capillary in terms of identification?
no tunica media nor adventitia - only and endothelial cell and basement membranes
often associated with satellite cells called pericytes
What is the function of a pericyte?
pericytes which may differentiate into endothelial of smooth muscle cells to repair tissues when capillaries are injured.
may have some contractile ability enabling change in diameter of the capillary to modify blood flow.
What are the three types of capillaries?
Continuous, Fenestrated, Sinusoid
What is the main function of continuous capillaries and where are they usually found?
May be completely continuous letting no blood product through but may als have intercellular clefts that selectively pass small molecules such as glucose, amino acids, or vitamins
Material may pass through the call through carrier mediated transport or transcytosis
Found in muscular, nervous and connective tissues.
What is the main function of fenestrated capillaries and where are they usually found?
formed by endothelial cells with pores also known as fenestrations allowing large molecules to pass while holding in blood and platelets
Found in small intestine, pancreas, endocrine glands, kidneys
Kidneys hace fenestrated capillaries for nutrient absorption, hormone secretion and waste filtration.
What is the main function of sinusoids and where are they usually found?
irregularly spaced shapes that fill in the spaces surrounding an organ - found in bone marrow, liver, spleen, lymph nodes, endocrine glands - allow molecules and blood to pass through
this is how newly formed blood cells and platelets get into the bloodstream and how the liver secretes albumin, globulins, and fibrinogen into the blood.
What are the main anatomical differences in arteries versus veins?
- Veins are more numerous and visible than arteries
- Veins are less muscular, more flaccid and more easily expandable than arteries
- approx. 70% of the body’s blood is in the veins at a given moment
- collapsed and irregular were arteries are round in cross section
What are the three classifications of veins?
Small, Medium, Large
Describe small veins.
also called venules - recieve blood from capillaries, have a thin endothelium surrounded by pericytes and reticular fibers
smooth muscle cells are scattered - becoming more continuous in larger venules
postcapillary venules which are immediately beyond the capillaries are porous and exchange material between blood and tissue
Describe medium veins.
- containing most anatomically named veins
- the tunica media having loosely organized smooth muscle mingled with collagen fibers and fibroblasts
- the tunica adventitia having loose collagenous and elastic fibers with a few muscle cells
- having valves to prevent back flow of blood - each valve is composed of two leaflets of tunica intima
Vascular bundles are composed of what?
medium veins and medium arteries traveling together in connective tissue
- may include a nerve - forming a neurovascular bundle. (slides artery and vein or artery, vein and nerve are cross sections of these bundles)
Describe large veins.
- relatively few but some examples are the iliac veins, the inferior vena cava, superior vena cava, pulmonary veins, internal jugular veins, renal veins, etc.
- poorly developed tunica media but a very thick adventitia (exceptions - great saphenous vein - has a well-developed tunica media)
- may have bundles smooth muscle in the tunica adventitia
What are the four variations in blood flow?
Portal Systems, Arteriovenous anastomosis, venous anastomoses, arterial anastomoses
Describe the flow of blood through the portal system. Give examples.
blood flows through two capillary beds in series before returning to the heart
e.g. between the brain hypothalamus and the pituitary, between the intestines and the liver
Describe the flow of blood through an arteriovenous anastomosis (shunt). Give examples.
blood detours around a capillary bed and flows directly into an artery and then into a vein - not exchanging material with any tissues
e.g. bases of the fingers, toes, ears - where the body first cuts blood flow to reduce heat loss
Describe the flow of blood through a venous anastomoses.
blood flows directly from one vein to another
e.g. back of the hand
Describe the flow of blood through an arterial anastomoses.
blood flows from one artery to another
e.g. around joints like the elbow and knee, coronary and cerebral circulation - if blood supply is cut off, another artery is used in its place to maintain the blood flow.
