Circulatory System Flashcards
What are the four functions of the circulatory system?
- Movement of fluids
- Regulation of temperature
- Distribution of molecules (hormones)
- Distribution of cells (immune system)
There are two functional components to the cardiovascular system. What are they?
- The blood vascular system
- The lymphatic vascular system
What are the primary differences between the blood and lymphatic vascular systems?
The blood vascular system circulates blood vessels that are pumped by a muscular organ, the heart
The lymphatic vascular system returns and transports lymph without a central pump; smooth muscle in vessel walls move lymph in one direction
Describe the common structure of blood vessels.
- Tunica intima - inner lining with single layer of flattened epithelial cells (endothelium)
- Tunica media - middle layer, mostly muscular
- Tunica adventitia - outer layer of supporting tissue
What are vasa vasorum?
Small arteries that run in the tunica adventitia and send arterioles and capillaries into the tunica media to provide nutrient and waste exchange
What are vasa vasorum important?
Diffusion from the lumen is insufficient to provide the tunica media with nutrition and waste elimination
________________ content exhibits the greatest variation from one part of the blood vascular system to the next
Muscle content
What is blood flow influenced by?
By variation in the activity of muscle tissue
Is there muscle in capillaries?
No
Is there muscle in the heart?
Yes, it’s literally all muscle
The ____________________ is located anterior to the chest wall and connects to the great veins and artiers; it has a free apex and sits in the pericardial sac
Heart
What are the four histological characteristics of cardiac muscle tissue?
Small
Mononucleated
Branched
Intercalated discs
What are the four muscular chambers of the heart?
Left atria
Right atria
Left ventricle
Right ventricle
The ________________ pump blood to the lungers and the body; the __________________ received blood from the lungs and the body
Ventricles
Atria
Walls of all four heart chambers consist of three major walls or tunics. What are they?
- Endocardium
- Myocardium
- Epicardium
The _________________________ is a single layer of squamous endothelial cells that sits on a thin layer of loose connective tissue that contains _______________ and collagen fivers and _____________ muscle cells
Endocardium
Elastic
Smooth muscle
The ______________________ is below the endocardium and connects with the myocardium; it contains small vessels, nerves, and importantly ________________ _____________
Subendocardium
Purkinjie Fibers
The ___________________ is the thickest of tunics in the heart and consists of _________________ muscle cells; it is much thicker in the ventricles than in the atria
Myocardium
Cardiac muscle cells
Why does the myocardium have an extensive capillary network?
The high oxygen demand of the myocardium
The ___________________ is the external layer of the heart and is composed of a simple squamous epithelium (_____________________) and supported by a thin layer of connective tissue
Epicardium
Mesothelium
The thin layer of connective tissue that supports the epicardium is composed of ____________________ tissue containing _________________ fibers
Fibrocollagenous tissue
Elastic fibers
What are papillary muscles?
Attachments for chordae tendinae (AV valves)
Myocardial thickness differs in individuals who are healthy or diseased; _____________________ results from long-standing physical exertion (athletes) and pathology (i.e., hypertension)
Hypertrophy
Muscle fivers are thicker and the nuclei are ________________ and _______________ in hypertrophied myocardium
Larger
Darker
The impulse-conducting system of the heart is responsible for what?
Generating the stimulus for contraction and spreading the contraction to the myocardium
What are the three major components of the cardiac conducting system?
- Sinoatrial node
- Atrioventricular node
- Atrioventricular bundle of His
Cells and fibers of the impulse-conducting system are modificed cardiac muscle cells functionally integrated by ____________ _____________
Gap junctions
The impulse rate of the conducting system is controlled by the __________________ nervous system
Autonomic
Describe the steps of the impulse-conducting system of the heart.
- The SA node in the right atrium generates the impulse
- The impulse spreads to the AV node in the right atrium
- The impulse is passed along the conducting fibers of the AV bundle of His, which divide into the left and right bundle branches that become the Purkinjie Fibers
What are the steps of the impulse conducting system?
The atrioventricular bundle of His splits into the left and right _______________ _____________ that become the ______________ ___________ that run beneath the endocardium and penetrate the myocardium
Bundle branches
Purkinjie fibers
The bundle branches are separated from myocardial fibers by a ______________ layer; they are specialized conducting fibers that contain few myofibrils and abundant ________________ granules and _______________
Fibrous
Glycogen
Mitochondria
_______________ _________________ are the terminal branches of the AV bundle branches located in the subendocardial connective tissue
Purkinjie fibers
What are the histological and structural characteristics of Purkinjie fibers?
Purkinjie fibers are large modified cardiac muscle fibers that cluster together in groups with one to two nuclei per cell
They contain a pale-staining central area with red stains on the cell periphery representative of myofibrils
Do Purkinjie fiber contain T-tubules and intercalated discs? If not, how do they communicate and connect with each other?
No, they are connected by desmosomes and gap junctions
The heart has four valves. What are they?
- The mitral valve
- The tricuspid valve
- The aortic valve
- The pulmonary valve
The mitral and tricuspid valves control blood flow from the ______________ to the _____________
Atria
Ventricles
The aortic and pulmonary valves control blood flow out of the _________________
Ventricles
______________ ______________ can be thought of as double-sided flattenings of the basic cardiovascular histological layers with different histological profiles to match their different physiological roles
Heart valves
What are the specialized features of heart valves?
They are primarily composed of a tough, specialized tunica intima in the absence of other vascular layers; the endothelium is continuyous with that of the cardiac wall while the collagenous layer toughens and becomes highly fibrous
Heart valves are primarily composed of a tough, specialized ______________ ____________ in the absence of other vascular layers; the ______________is continuous with that of the cardiac wall while the _______________ layer toughens and becomes highly ________________
Tunica intima
Endothelium
Collagenous
Fibrous
Identify the blood vessel tunic:
–1 layer endothelial cells
–Supported by subendothelial CT layer (Loose CT) with occasional smooth muscle cells
Tunica intima
What do the tunicas intimas of the arteries have that those of veins?
In arteries, the internal elastic lamina separates the intima from the media
Identify the tunic of the blood vessel:
–Middle layer
–Concentric layers of smooth muscle cells
Tunica media
What do the tunica media of arteries contain that veins do not?
A thinner external elastic lamina that separates the media from the adventitia
Identify the blood vessel tunic layer:
–Type 1 collagen and elastic fibers
–Gradually continuous with stromal CT of organ through which the vessel runs
Tunica adventitia
Large vessels usually have ______________ _____________ or “vessel of the vessel” and a network of __________________ sympathetic nerve fibers to control _________________
Vasa vasorum
Unmyelinate
Vasoconstriction
What is the function of the arterial system?
To distribute blood from heart to capillary beds throughout the body
The pumping action of heart produces pulsatile blood flow in arterial system: the contraction of ventricles is known as ______________ (blood forced into arteries and arterial walls expand), and the recoil of the arterial walls is known as _____________
Systole
Diastole
What regulates the flow of blood to organs and tissues?
The diameter of the distributing vessels
The arterial system vessel walls conform to the general three-tunic structure but are characterized by increased ___________________ and a thicker ______________ _____________ wall relative to lumen diameter
Elastin
Smooth muscle
There are three types of arterial vessels. What are they?
Elastic artery
Muscular artery
Arteriole
The ______________ arteries are the major distribution vessels of the arterial system; they help stabilize blood flow and include the aorta, brachopephalic trunk, common cartoid artery, subclavian artery, and large pulmonary arteries
Elastic
The tunica media of elastic arteries contain many _______________ fibers
Elastic fibers
How is the tunica intima of elastic arteries different from those of muscular arteries?
The tunica intima of elastic arteries is much thicker than those of muscular arteries
The aorta is a prime example of an elastic artery. The tunica intima is composed of a single layer of flattened endothelial cells that are supported by a layer of ___________________ tissue rich in _______________; its subendothelial supportive tissue contains _______________ and ________________ cells that are structurally similar to smooth muscle cells
Collagenous
Elastin
Fibroblasts
Myointimal cells
The subendothelial layer in the elastic artery, the aorta, contains two cell types. What are they?
Fibroblasts
Myointimal cells (similar to smooth muscle cells)
The _____________ ___________ of elastic arteries is broad and extremely elastic, and the ____________ _____________ of elastic arteries is collagenous with small vasa vasorum, which penetrate the outer half of the tunica media
Tunica media
Tunica adventitia
_________________ arteries are the main distributing branches of the arterial tree
Muscular
_______________ arteries have very thin intimas with adventitia layers of various thickness
Muscular
Whereas elastic tissue is found nearly throughout elastic arteries, how is elastic tissue organized in muscular arteries?
Elastic tissue is concentrated into two well defined elastic sheets:
Internal elastic lamina (IEL) (between the intima and media)
External elastic lamina (EEL) (between media and adventitia)
What are some examples of muscular arteries?
Radial
Femoral
Coronary
Cerebral
Small muscular arteries have a thin but distinct _________________________ but little or no _____________________ while their medias contain three to 10 layers of smooth muscle with nearly no ________________ _______________
Internal elastic lamina
External elastic lamina
Elastic fibers
____________________ contain only one to two layers of smooth muscle and are the primary site of vascular resistance
Arterioles
Explain the flow of blood from aorta to capillary.
Elastic artery
Large muscular artery
Small muscular artery
Large arteriole
Small ateriole
Capillary
As muscular arteries merge into larger arterioles and smaller arterioles, there is a gradual loss of the ______________ _______________ ______________ and a reduction in the number of ____________ ___________ in the ______________
Internal elastic lamina
Muscle layers
Media
Larger arterioles have only __ to __ layers in their medias with very thin _______________ that are sometimes indistinguishable from the surrounding collagenous fibrous tissue
Two to three
Adventitia
______________________ are thin-walled vessels forming interconnected networks for the exchange of gases, fluids, nutrients, and metabolic wastes
Capillaries
How is the blood flow of capillaries regulated?
Via the arterioles and precapillary sphincters
To what do capillaries drain into?
Postcapillary venules
Collecting venules
Small muscular venules
What blood vessels are the only ones that permit exchange?
Capillaries
There are two main types of capillaries. What are they?
Continuous
Fenestrated
Flow in capillaries is by arterioles and muscular sphincters called ______________ ______________
Precapillary sphincters
_______________ are composed of a single layer of endothelial cells rolled up in the form of a tube
Capillaries
Thin walls and slow blood flow favors _____________ in capillaries
Exchange
Does blood move fast or slow in capillaries?
Slow
What are pericytes?
Pericytes are contractile cells that wrap around the endothelial cells of capillaries and venules that regulate capillary blood flow, the clearance and phagocytosis of cellular debris, and the permeability of the blood–brain barrier
What are the functions of pericytes?
To regulate the flow of blood in capillaries, the clearance and phagocytosis of cellular debris, and the permeability of the blood-brain barrier
Where are pericytes embedded?
The basement membrane
How do pericytes communicate with endothelial cells?
Direct physical contact
Paracrine signaling
Most regions of the body are supplied by ____________________ capillaries that contain a complete lining, where they regulate the exchange of material, and maintain a distinct continuity with endothelial cells
Continuous capillaries
______________________ capillaries contain “windows” or pores that permit the rapid exchange of water and solutes
Fenestrated
Where are fenestrated capillaries found?
In tissues where rapid interchange of substances occurs between the tissues and blood (e.g., kidney, intestine, choroid plexus, endocrine gland)
The _______________ system of the cardiovascular system is the low pressure component that carries blood from capillaries back to the right atrium of the heart
Venuous
How does blood flow against gravity in the venuous system?
Contractions of smooth muscle in vein walls and the external compression of veins by surrounding skeletal muscle
How is backflow prevented in the venuous system?
The presence of valves
Why is it important to move (in regards to the venuous system)?
Skeletal muscle compression of veins assists in blood flow
While veins maintain the general three-layer structure of blood vessels, how do they differ from arteries?
They have less elastic and muscular components
Which system contains a larger portion of blood: the arterial or venuous system?
Venuous
PV = nRT
(Less pressure = more volume)
What are venules?
The smallest venous vessels that collect blood from capillary beds
What is a characteristic feature of all venules?
Large diameter of the lumen compared to the overall thinness of the wall
The transition from capillaries to _______________ occurs gradually and the immediate _______________ _______________ are structually similar to capillaries but with larger diameters
Venules
Postcapillary venules
Postcapillary venules converge into larger __________________ _______________ that have more contracile cells
Collecting venules
Venules become surrounded by recognizable tunica medias with two or three smooth muscle layers and are called __________________ venules
Muscular
Blood entering veins is under very low _________________
Pressure
How does blood move towards the heart in veins?
Via contraction of the tunica media and external compressions from surrounding muscles and organs
______________ project from the tunica intima to prevent the back flow of blood
Valves
Most veins are ____________ or _____________ veins and are usually located in parallel with corresponding muscular arteries
Small
Medium
What are the primary differences between venules and veins?
Venules contain a clealy difined intimal layer but no elastic fibers; the tunica media contains one to two smooth muscle layers
Veins have a thicker muscular wall with poorly developed internal elastic lamina
In ________________-sized veins the tunica intima is hard to discern and the tunica media is compared to an artery
Medium
Medium-sized veins have two to four layers of smooth muscle fibers arranged circumferentially, and the ____________ _____________ is usually the thickest layer
Tunica adventitia
_______________ veins are big venous trucks paired with elastic arteries close to the heart
Large
Large veins have a well-developed tunica intima but a relatively thin _______________ ______________ with few layers of smooth muscle and abudant connective tissue
Tunica media
