Cardiovascular System and the Heart Flashcards
State the composition and function of the Cardiovascular system
The Cardiovascular system consists of the Heart and blood vessels.
- Heart- propels blood through the system
- _Arteries_ (Away from the heart)- vessels that carry blood to the tissue
- Capillaries- smallest vessels, sites of O2, CO2, nutrient, & waste products exchange between blood & tissues
- Veins- carry blood to the heart
Functions:
- It is responsible for providing O2 and metabolic nutrients to the body
- It removes CO2 and metabolic waste products from tissues
2 Dual circulations of the Cardiovascular sytem
-
Systemic circulation- supplies blood to all peripheral tissues, including the lungs:
* Pulmonary veins- Left Atrium- Mitral valve- Left ventricle- Aortic semilunar valve- Aorta- Arteries- Arterioles- Capillaries -
Pulmonary circulation- supplies blood to lungs for gas exchange:
* Venules- Veins- Inferior and Superior vena cava- Right atrium- Tricuspid valve- Right ventricle- Pulmonary semilunar valve- Pulmonary arteries- Lungs
Valves- LAB RAT
3 layers of the Blood vessel and their components
Tunica intima (closest to the lumen)
-
Endothelium (simple squamous epithelium) connected by tight junctions
- Basal lamina of the endothelium
- Subendothelial layer of loose connective tissue
- contains an INternal elastic lamina (IEL) in some
- Site of atherosclerotic plaque formation
Tunica Media (middle layer)
- Smooth muscle layer arranged in concentric layers
- Gap junctions between smooth muscle cells (SMC)
- Sheets of reticular fibers, elastic fibers, ground substances (proteoglycans) and lamellae are intertwined between layers of (SMC)
- Thickest layer for arteries vs. tunica adventitia for venules and veins
- contains an EXternal elastic lamina (EEL) in some
- Smooth muscle regulates the diameter of blood vessel [more diameter = more blood flow] [less diameter = less blood flow]
Tunica Adventitia/Externa (outermost layer)
-
Dense irregular connective tissue (longitudinal collagen type 1 fibers with elastic fibers and fibroblasts)
- Thickest layer of venules and veins vs. tunica media for arteries
-
Larger vessels’ tunica adventitia contain:
- Nervi vasorum/vascularis- unmyelinated sympathetic nerve fibers (vasoconstrictor- NE)
- Vasa Vasorum- “vessel of the vessel”- blood vessel (arterioles, capillaries, venules) that provide perfusion to larger blood vessels (aorta, SVC, IVC)
Compare and contrast Large arteries, Medium arteries, Small arteries and arterioles
Large Arteries (Elastic arteries)- arteries that branch directly off the heart (aorta and pulmonary arteries)- Conduct blood from heart and with elastic recoil to help move blood forward under steady pressure
- Tunica intima- Thick and IEL is not always discernable
-
Tunica media- contains multiple sheets of elastic laminae; External elastic lamina is not always discernable
- Enables stretching to accomomdate a large volume of blood ejected from the ventricles during systole, which can recoil during diastole to maintain continuous pulsatile blood flow
- Tunica adventitia- Thin; contains vasa vasorum and nervi vasorum
Medium Arteries (Muscular arteries) - branch form large arteries to provide blood flow to specific regions and organs (axillary, radial, femoral, carotid, renal, mesenteric, & coronary arteries)- Distribute blood to all organs and maintain steady blood pressure and flow with vasodilation and constriction
- Tunica intima- prominent internal elastic lamina
-
Tunica media- contains 3-40 layers of smooth muscle with elastic laminae that decrease in number as the artery size decreases
- External elastic lamina present between tunica media and tunica adventitia
- Tunica adventitia- Prominent; can be equal to or less than the thickness of the tunica media
Small Arteries (Distribute blood to arterioles) &
Arterioles (Resist and control blood flow to capillaries)
- Tunica intima- Small arteries contain prominent internal elastic lamina- Arterioles do NOT
- Tunica media- Small arteries contain up 3 to 8 layers of smooth muscle- Arterioles only contain 1-2 layers
- Tunica adventitia- thin layer that blends with surrounding connective tissue for both
Important role of Arterioles
Arterioles regulate blood flow through capillaries via contraction (vasoconstriction) and relaxation (vasodilation) of the smooth muscle layer of their tunica media
Major site of vascular resistance that play large roles in hypertension and shock
Increase blood flow = decrease resistance
Decrease blood flow = increase resistance
Metarterioles
Metarterioles are short vessels that link arterioles to capillary beds with thickened tunica media layer called a precapillary shincter, which regulate capillary blood flow
Contract-relax 5-10cycles/min in a pulsatile manner
When sphincters are closed, blood flow directly to the Thoroughfare channel (lack muscle) which is connected to the postcapillary venules
Capillaries
Capillaries:
- Smallest diameter blood vessels
- Flattened nuclei; Heterochromatic
- Sites of exchange of gases, metabolites, & waste products between the blood and peripheral tissues
- Consist of a single endothelial cell with a surrounding basal lamina layer with tight junction for permeability
- Cytoplasm contains mitochondria and vesicles
- Increased metabolic demand = Increased capillary density
- Classified into 3 categories based on permeability
- Continuous
- Fenestrated
- Discontinuous
3 Histological types of Capillaries
- Continuous capillaries (least permeable):
- Endothelium bound together by occluding (tight) junctions
- Surrounded by continuous basal lamina
- Pinocytic vesicles are found beneath the lamina and basal membrane surfaces to facilitate the exchange of larger molecules between the blood and surrounding tissue
- Found in the CNS (BBB), lung*, *muscle*, & *cortex of thymus
- Fenestrated capillaries:
- Endothelium with numerous fenestrations that facilitate rapid exchange of molecules
- Surrounded by a continuous basal lamina
- Found in the kidney*, *endocrine tissue*, *intestinal villi*, & *choroid plexus
- Discontinuous capillaries:
- Endothelium with large fenestrations and no diaphragms
- Discontinuous gaps exist between endothelium (inter-endothelial gaps)
- Discontinuous and sometimes absent basal lamina
- Reticular fibers present
- Enable easy phagocytosis of blood molecules
- Found in liver*, *bone marrow, & spleen
Pericytes
Pericytes:
- Located along continuous capillaries and postcapillary venules
- Mesenchymal cells with long cytoplasmic processes surrounding the endothelial layer
- Secrete many ECM & form their own basal lamina which fuses with the basement membrane of the endothelial cells
- Cytoskeletal component of myosin, actin, tropomyosin (indicates that pericytes dilate or constrict capillaries helping to regulate blood flow)
- Important for maintaining the BBB in the CNS
- Proliferate and differentiate to form smooth muscle after injury
Diabetic microangiopathy
Diffuse thickening of capillary basal lamina and decrease in metabolic exchange at the vessels (affecting kidneys, retina, skeletal muscles, skin)
Excessive blood sugar that occurs with diabetes (hyperglycemia) can lead to this
Primary site of diapedesis
Post- capillary venules are the primary site of diapedesis
Junction between the endothelial cells of post-capillary venules are the looses of the microvasculature as it facilitates transedothelial migration of leukocytes during inflammation
Compare and contrast Venules, Small and medium veins, Large veins
Venules:
- First vessel of the venous system that drain capillary blood
- Vessel wall is often as thin as a capillary, but a much larger lumen
- Can transition from low permeability to high permeability when stimulated by vasoactive molecules (histamine)
- Post-capillary venules are the primary site of diapedesis
- Tunica intima- very thin; NO internal elastic lamina
- Tunica media is comprised of 1-2 bundles of smooth muscle cells and pericytes with longitudinal collagen fibers; No external elastic lamina
- Tunica adventitia- indistinct to none
Small/Medium veins:
- Veins that drain tissues/organs into the large veins
- Contain one way endothelial line valves formed by the thin tunica intima layer to enable unidirectional flow
- Prevents retrograde flow due to gravity in the lower extermities
- Tunica media consists of 3-5 layers of smooth muscle cells, collagen, and elastic fibers that is perfused by the vasa vasorum
- Tunica adventitia is thicker than the tunica media with some longitudinal smooth muscle
Large vein:
- Thin tunica intima; indistinct internal elastic lamina
- Tunica media- several layers of smooth muscles; indistinct external elastic lamina
-
Tunica adventitia is the thickest layer, up to 4X the thickness of the tunica media
- Prominent bundles of longitudinal smooth muscle
- Contain collagen and elastic fibers, nerves, and vasa vasorum
- Examples: Superior and inferior vena cavae, mesenteric, renal, femoral, portal, and internal jugular veins
Systole and Diastole
Pressure gradient between atria and ventricles- main driver of blood flow into the ventricles
Blood flow is moved through the arteries forcefully during contraction (Systole)
- aortic and pulmonary valves opened
- tricuspid and mitral valves closed
Venricular pressure drops to a low level the ventricles relax (Diastole):
- aortic and pulmonary valves closed
- tricuspid and mitral valves opened
- pressure in atria is greater than pressure in ventricles (Pa>Pv)
- Elastin rebounds passively to maintain arterial pressure
- Aortic and pulmonary valves prevents backflow of blood so the rebound continues the blood flow away from the heart
Difference of pressure requirement in correlation with the functions of arteries and veins
Arteries are distributing system (higher pressure)
Veins are collecting system (higher volume so need lower pressure)
Pressure in artery > pressure in vein that’s why arteries need much stronger wall to stand pressures
Atherosclerosis
Atherosclerosis
- Disease of elastic arteries (large) and muscular arteries (medium)
- Buildup of plaque within arterial walls that leads to wall hardening and subsequent narrowing of the vessel wall
- Endothelial damage leads to macrophages entering the tunica intima and platelets adhering to the damaged endothelium triggering and inflammatory response
- Causes of endothelial damage- oxidized LDL, hypertension, smoking
- Inflammatory cells stimulate hyperplasia of smooth muscle cells then migrate to the tunica intima
- Macrophages engulf cholesterol to form foam cells that appear as fatty streaks
- Atheroma: Smooth muscle cells and macrophages release cytokines that stimulate production of extracellular matrix components that form a fibrous cap over a necrotic center (cellular debris, cholesterol, foam cells)
- Rupture of fibrous cap and release of the necrotic center components stimulate thrombus formation and subsequent vessel occlusion and ischemia
Aortic Aneurysm
Aortic Aneurym
- Pathologc dilation of the aorta that can occur at any point along the aorta but most commonly seen in the abdomen (AAA-abdominal aortic aneurysm)
- Major risk factors: hypertension, smoking, diabetes, and hyperlipidemia
- Aortic dissection occurs when a break in the tunica intima allows blood to leak into the tunica media layer, resulting in abnormal dilation of the aorta
Identify the type of vessel
Medium artery-
- thicker tunica media (smooth muscle layer), rounder lumen
- Internal elastic lamina in the Tunica Intima is very prominent in medium artery- histological marker of medium or muscular arteries
Identify the type of vessel
Medium vein-
- thinner tunica media (smooth muscle layer), almost stellate-shaped lumen
- very thin tunica intima
Identify the histological marker of this vessel
Internal elastic lamina in the Tunica Intima is very prominent in medium artery- histological marker of medium or muscular arteries
Identify the type of vessel
Arterioles (surrounded by adipocytes)- endothelium and 1 layer of smooth muscle
Identify the type of vessel
Large artery
- Significant tunica intima
-
Tunica media- contains multiple sheets of elastic laminae
- Enables stretching to accommodate a large volume of blood ejected from the ventricles during systole, which can recoil during diastole to maintain continuous pulsatile blood flow
Identify the type of vessel
Large vein
- Very thin intima, very thin media, very large adventitia (hallmark for large vein)
- 2 layers of smooth muscle- 1 in media and 1 in adventitia (bundles of smooth muscle interspersed between the dense irregular connective tissue running at a 90 degree angle to the tunica media- orthogonal)
Identify the type of vessel
Small artery-
- prominent internal elastic lamina, there is not much smooth muscle to qualify for medium artery
Identify the 2 vessels
Venule (left)
Arteriole (right)- with 1 layer of smooth muscle below the endothelium and much more defined lumen
Identify the types of vessel
Capillary- literally 1 cell (single endothelial cell)
Arteriovenous shunt, Venous portal system, Arterial portal system
Arteriovenous shunt (Arteriovenous anastomoses):
- thermoregulation by the skin (arterioles bypass capillary network & connect directly to venules
- richly innervated by sympathetic and parasympathetic nerve fibers
- controls degree of vasoconstriction of the shunts or precapillary sphincter regulating blood flow through the capillary beds
- Providing blood to where they are needed:
- Sympathetic nerve fibers close shunts or relax precapillary sphincters to the to radiate heat when hot
- Sensory nerve fibers open shunts to save heat when cold
- Contraction of precapillary sphincters = open AV shunt during cold weather
- decrease blood flow (precapillary sphincter is constricted or shut)- conserve heat
- Relaxation of precapillary sphincters = closed AV shunt during hot weather as heat is dissipated
- increase blood flow (precapillary sphincter is relaxed )- more heat dissipated
- Contraction of precapillary sphincters = open AV shunt during cold weather
- Providing blood to where they are needed:
Venous portal system:
- blood flow through 2 successive capillary beds separated by a portal vein
- allow for hormones or nutrients picked up by the blood in the 1st capillary network to be delivered most efficiently to cells around the 2nd capillary bed before blood is returned to the heart for general distribution
- important in anterior pituitay gland and liver
Arterial portal system:
- Afferent arteriole- capillaries- efferent arteriole (kidneys)
Carotid sinuses
Carotid sinuses:
- slight dilations of the bilateral internal carotid arteries where they branched from the (elastic) common carotid arteries
- act as important baroreceptors (monitors blood pressure)
- tunica media is thinner (allowing great distention when bp rises)
- adventitia contains sensory nerve endings from cranial nerve IX (glossopharyngeal nerve)- vasomotor processes afferent impulses and adjust vasoconstriction- maintaining normal bp
- similar baroreceptor- aortic arch via cranial nerve X (vagus nerve)
Carotid bodies and Aortic bodies
Both have chemoreceptors (monitor blood CO2, O2, pH levels)
- Part of the autonomic nervous system (paraganglia with rich capillary network)-
- Surrounded by large neural crest-derived glomus cells (filled with vesicles containing NT)-
- Ion channels in glomus cell membrane respond to stimuli in arterial blood by activating release of NT to correct hypoxia (decrease O2), hypercapnia (increase CO2) or acidosis
- Sensory fibers branching from the glossopharyngeal nerve (carotid) and from the vagus nerve (aortic) form synapse with the glomus cells and signal brain center to initiate cardiovascular and respiration adjustments
Varicose veins
On a healthy vein:
- valve opens as muscles squeeze vein, blood moves upward
- valve closes as muscles relax, blood cannot leak downward
On varicose veins:
- valves don’t close properly, blood leaks downward
Edema
Hydrostatic pressure and oncotic pressure are opposing forces in blood vessels. Under normal conditions, hydrostatic pressure (pressure from the heart tends to push fluid out of the capillary (filtration) whereas oncotic pressure tends to pull fluid into the capillary (reabsorption)
Albumin helps keep water inside the blood vessels.
When albumin is low:
- water seeps out of blood vessels
- Low blood volume symptoms
- Symptoms of swelling from too much water outside blood vessels
Lymphatic vessels
Lymphatic vessels:
- Thin walls and increasing amounts of CT and smooth muscle with no outer tunica (undefined separation of tunics)
- Have valves comprised of complete intimal folds
- 2 large trunks:
- thoracic duct - connects with the blood circulatory system near the junction of the left internal jugular vein with the left subclavian vein
- right lymphatic duct- enters near the confluence of the right subclavian vein and the right internal jugular vein
- Adventitia is underdeveloped
- Contains vasa vasorum and neural networks
- Major distributor of lymphocytes, antibodies, and other immune components
Lymph nodes
where lymph is processed by cells of the immune system
3 Major layers of the walls of all four heart chambers
- Endocardium
- Innermost layer beginning the endothelium facing the lumen of the cardiac chambers (analogous to the tunica intima of blood vessels)
- Deep subendocardial layer of connective tissue
- Dense irregular CT and Loose CT
- Purkinje fibers
- Myocardium
- Cardiac muscle layer (with Loose CT and continuous capillaries) arranged spirally around each heart chamber (analogous to tunica media of blood vessels)
- Thickest (much thicker in left ventricle d/t need of strong forces)
- May see Purkinje fibers (modified cardiomycocyte)
- Endomycium, Perimycium, Epimysium
- Epicardium
- Outermost layer (analogous to the tunica adventitia of blood vessels)
- (Simple squamous eptihelium) Mesothelium
- Subepicardial layer (Loose CT, Dense irregular CT, or Unilocular CT)
- Same as visceral layer of the pericardium
- Pericardium from the inside out:
- Serous pericardium (visceral and parietal)
- Continuous with the visceral layer (surrounding the heart) of the serous pericardium (produces the serous fluid)
- Pericardial cavity
- Parietal layer of serous pericardium fuses with the fibrous pericardium
- Fibrous pericardium
- Adipose tissue
- Serous pericardium (visceral and parietal)
Pericardial effusion and Cardiac tamponade
Pathological situations (buildup of fluid or blood on the pericardial space):
Pericardial effusion- build up of fluid
Cardiac tamponade- build up of blood which puts pressure on the heart that may prevent it from pumping effectively
Conducting System of the Heart
Conduction system of the heart generates waves of depolarization that spreads through the myocardium to stimulate rhythmic contraction and does NOT require neural input
Right atrium:
Sinoatrial (SA) node
- Close to the superior vena cava
- Contains pacemaker (modified mycocytes) that initiates the electrical impulse that results in a heartbeat.
- Few sarcomeres, few myofibrils. Smaller than cardiac muscle cells.
- Heart rate and cardiac contractility are modulated by autonomic innervation here- sympathetic increase rate, parasympathetic decrease rate
Atrioventricular (AV) node
- Slows the electrical impulse when it arrives from the internodal pathways (less gap junctions and fiber is small)
- Waiting for the atria to empty the blood to the ventricles
AV bundle (Bundle of His) -
- On interventricular septum
- Conducts impulse from the AV node to the bundle branches
Left bundle branch - extends toward the apex of the heart and then radiates across the inner surface of the left ventricle
Right bundle branch - extends toward the apex of the heart and then radiate across the inner surface of the right ventricle
Moderator band - replays the stimulus through the ventricle to the papillary muscles, which tense the chordae tendinae before the ventricles contract
Purkinje fibers - convey the impulses very rapidly to the contractile cells of the ventricular myocardium
Purkinje fiber mycocytes - carry the action potential from the pacemaker cells to myocardial myocytes via gap junctions at intercalated disks.
Cardiac skeleton
Structural framework composed of dense irregular connective tissue
Forms the fibrous annuli of the atrioventricular valves, trigonal fibrosa (the middle portion), and the septum membranaceum (separates different chambers of the heart)
Insulation between the atria and ventricles- separates contraction of atria and ventricles (blocking the transaction of action potentials)
Atrioventricular valves
Atrioventricular valves:
- Mitral valve (bicuspid valve or left atrioventricular valve which lies between Left atrium and Left ventricle for Systemic circulation)- [LeMBS for mnemonics _L_eft _M_itral or _B_icuspid _S_ystemic] and
-
Tricuspid valve (or right atrioventricular valve lies between Right atrium and Right ventricle for Pulmonary circulation)- [RiT Pul for mnemonics Right Tricuspid Pulmonary]
- Prevent backflow of blood into tht atria during ventricular contraction
- Order of subendothelial connective tissue layers from atria to ventricle: Fibrosum- Spongiosum- Ventricularis (FSV)
- Ventricularis layer is continuous with chordae tendinae
Functions of Chordae tendinae
- Anchoring and supporting the valves
- Frim points of insertion for cardiac vessels
- Electrical insulation between atria and ventricles (coordinate beat)
Semilunar valves
Semilunar valves:
- Aortic- prevents backflow of blood from aorta into the ventricles during diastole
-
Pulmonary - prevents backflow of the blood from pulmonary artery into the ventricles during diastole
- Order of subendothelial connective tissue layers from atria to ventricles:
- Spongiosum- Fibrosum- Ventricularis (SFV)-
- mnemonic “soft moon :)” Spongiosum Lunar (moon)
- Order of subendothelial connective tissue layers from atria to ventricles:
Identify the outer layer
Endothelial cells in the Endocardium
Identify tissue
Cardiac muscle
Cross section of cardiac muscle- nuclei at the center of the cell
Identify type of vessel
Vein-
thin layer of the vessel wall, large irregular shape of the lumen
Identify tissue
Cardiac muscle
Longitudinal sections of cardiac muscle, 1 or 2 nuclei per muscle cell, striations
Identify the structure on the tip of yellow and blue arrows
Blue: Intercalated discs- areas of high density of gap junctions
Yellow: Lipofucsin granules- cholesterol and fats that are build up in the organ overtime especially with cardiac muscle which has very poor capacity for regeneration
Identify
Purkinje fiber-
- fibers are not as densely packed as regular cardiac myocyte
- Pale staining d/t high concentration of glycogen
- Larger, paler-staining nuclei
Identify
- Endocardium
- a. Endothelium
- b. Subendocardial layer of of connective tissues and scattered smooth muscle cells
- c. Purkinje fibers
Identify
- Myocardium (cardiac muscle fibers)
- Epicardium (same as visceral layer of pericardium)
- d. Mesothelium (simple squamous epithelium)
- e. Subendocardial connective tissue - Loose and Adipose connective tissues
Fill in the boxes
Identify layer
Endocardium
Identify layer
Myocardium
Identify the indicated blue region
Subepicardial tissue layer
Identify layer
Peicardium
Identify and state why
Heart Valve
because there is no mucle only Loose CT and Dense irregular CT
Identify location
Right ventricle
d/t the valve and not apparent thickness
Identify the topmost layer
Mesothelium
notice the Unilocular adipose tissue
Identify
Valve
Endothelium (both sides)
Loose CT- Dense CT
No muscle
Identify location
Left ventricle
- notice the thickness
Identify
Chordae tendinae
- composed of dense irregular CT
Identify
Aortic valve
- left ventricle which is a part of systemic circulation that passes through aortic semilunar valve
does not have chordae tendinae so not any atrioventricular valve (mitral or bicuspid)
