Cardio-Histology Flashcards
Which direction of flow for arteries?
Carry blood away from the heart
Which direction of flow for veins?
Carry blood toward the heart
What is the main job of the lymphatic system?
collects excess interstitial fluid and returns it to the venous system.
What is the function of the auricles?
Increases the capacity of atria when needed
The pulmonary veins leading into the left atrium do/do not have valves?
do not
What is systolic BP?
ventricles are squeezing out blood under high pressure
What is diastolic BP?
blood pressure when ventricles filling up with more blood
What adult structures come form the primordial heart?
Adult heart Ascending aorta & Pulmonary trunk (proximal portions).
What adult structures come from the Aortic sinus?
Arteries of systemic and pulmonary circulation
What is the primordial heart?
— single, muscular tube with multiple dilations and constrictions
What is the aortic sinus?
receives blood from primordial heart Pharyngeal arch arteries (6 pairs) Dorsal aortas (1 pair)
What adult structures are from the cardinal veins?
Veins of the systemic circulation
What are the cardinal veins?
bilateral series of intraembryonic vessels that converge and drain into the primordial heart
What adult structures are from the umbilical arteries and veins?
Umbilical ligaments (medial umbilical folds) Round ligament of the liver & ligament venosum
What is the function the umbilical arteries and veins?
connects intraembyonic vasculature to uteroplacental vasculature
What is the function of the vitelline arteries and veins?
connects the intraembyonic vasculature to yolk sac vasculature
What adult structures come from the vitelline arteries and veins?
Arteries of the GI: celiac, sup. & inf. mesenteric Hepatic portal venous system and hepatic veins
What stuctures do the pulmonary veins derive from?
directly from or associated with the primordial heart
Practice naming each stucture
What adult structures come from the sinus venous?
Smooth portion of right atrium and crista terminalis
What adult structures come from the primordial atrium?
Rough (pectinate) portion of right and left atrium Pulmonary veins contribute to smooth portion of left atrium*
What adult structures arise from the atrioventricular canal with endocardial cushions?
Atrioventricular valves
What adult structures arise from the primordial ventricle?
Rough (trabecular) portion of right and left ventricular walls; interventricular septum and papillary muscles
What adult structures areise from the bulbus cordis?
Smooth portion of the right and left ventricular walls; proximal portion of great arteries and their cardiac (semilunar) valves
What adult structures arise from the truncus arteriosus (outflow)?
Next portion of great arteries above the cardiac (semilunar) valves
What is the primordial heart?
a single, folded muscular tube, contained with a pericardial sac with a series of constrictions and dilations dividing the primordial heart into 6 regions
What are the 6 regions of which the primordial heart is divided?
- sinus venousus
- Primordial atrium
- Atrioventricular canal
- Primordial ventricle
- Bulbos cordis
- truncus arteriosus
Sinus venosus — receives the venous blood from the system and becomes incorporated into the smooth portion of the right atrium that is continuous with the coronary sinus and the superior and inferior venae cavae. The crista terminalis demarcates the transition between the contributions from from the sinus venous and primordial atrium
Cardinal
Sinus venosus — receives the venous blood from the cardinal system and becomes incorporated into the smooth portion of the right atrium that is continuous with the and the superior and inferior venae cavae. The crista terminalis demarcates the transition between the contributions from from the sinus venous and primordial atrium
coronary sinus
The crista terminalis demarcates the transition between the contributions from from the and .
Sinus venous and primordial atrium
What is the primordial atrium?
gives rise to the rough, pectinate portions of the left and right atria (e.g. the auricles).
What is the atrioventricular canal?
initially a single connection between the primordial atrium and ventricle.
What divides the atrioventricular canal into left and right?
Growth of endocardial cushions from the anterior and posterior walls
What is the function of the primordial ventricle?
— gives rise the muscular walls of the left and right ventricle and the muscular portion of the interventricular septum.
What is the function of the bulbos cordis?
the bulbus cordis contributes to the smooth portion of the ventricles and proximal portions of their output vessels near their semilunar valves
the bulbus cordis contributes to the smooth portion of the ventricles and proximal portions of their output vessels near their semilunar valves: What output vessels?
Right ventricle — conus arteriosus and pulmonary trunk
Left ventricle — aortic vestibule and ascending aorta
What does the truncus areteriosus give rise to?
contributes to portions of the ascending aorta and pulmonary trunk above their semilunar valves
What are the names of the two atrial septa that divide the primordial atrium?
- Septum primum
- Septum secundum
What is the septum primum?
outgrowth from the superoposterior of the atrial wall toward the fused endocardial cushions of the atrioventricular canals.
What is the septum secundum?
second outgrowth that forms to the right of the septum premium. This septum is not complete and gives rise to the foramen ovale.
What allows for bypass of the pulmonary circuit during fetal circulation?
Septum primum, septum secundum, and foramen ovale
What is the foramen secundum?
a portion of the septum primum (that divides the atria) that degenerates
What is the growth pattern of the interventricular septum?
arises from the inferior walls of the primordial ventricle and grows toward term endocardial cushions of the atrioventricular canals.
The muscular interventricular septum does/does not completely separate the ventricles?
Does not
The interventricular foramen persists until growths from the and fuse to form the membranous part of the interventricular septum.
endocardial cushions, left/right bulbar ridges
How are the great arteries (ascending aorta and pulmonary trunk) formed?
within the bulbus cordis and truncus arteriosus, the bulbar and truncal ridges grow in a spiral pattern that divides them into the proximal portions of the pulmonary trunk (outflow for the right ventricle) and ascending aorta (outflow for the left ventricle).
From what outgrowth do the atrioventricular valves form?
the endocardial cushions and atrioventricular canals.
Which embryonic structures form the semilunar valves?
as outgrowth within the bulbus cordis and bulbar ridges.
The migration of which type of cells is crucial for the proper development and formation of the bulbar and truncal ridges, valves, and the membranous portion of the interventricular septum?
The neural crest cells
What type of process creates connections and branches throughout the developing coneptus?
Angiogenesis
Which 3 major embryonic divisions does the vasculature system arise?
- Pharyngeal arch arteries and Dorsal Aortas
- Cardinal veins
- Vitelline arteries and veins
The truncus arteriosus is continuous with the aortic sac, from which paired pharyngeal arch arteries arise, each associated with development of the pharyngeal arches
6
The truncus arteriosus becomes the?
Distal pulmonary trunk and ascending aorta
The aortic sac becomes the?
mid ascending aorta and distal brachiocephalic artery
The Dorsal aortas become the?
portions of the descending trunk, the right subclavian artery, and the distal internal carotid arteries.
The 3rd pharyngeal arch arteries become?
the left and right common carotid arteries
The 4th pharyngeal arteries become the?
incorporate into the arch of the aortic arch
The 6th pharyngeal arch arteries become?
bifurcation of the right and left pulmonary artery as well as the ductus arteriosus and later ligamentum arteriosum
What are the embryonic cardinal veins?
a complex system of bilateral intraembryonic veins that eventually converge into a single common cardinal vein that drains into the sinus venous of the primordial heart
What are the adult structures from the cardinal veins?
The systemic venous system: superior and inferior vena cava; azygous & hemiazygous veins; coronary sinus, etc
What are the vitelline arteries and veins?
connection between the intraembryonic vasculature and the extraembryonic vasculature, primarily the yolk sac.
What adult structures come from the vitelline artery?
connects to the abdominal portion of the descending aorta and contributes to the formation of vascular supply to the GI System, i.e the celiac a., superior mesenteric a. and inferior mesenteric a.
What adult structures come from the vitelline veins?
empty into to the common cardinal vein and contributes to the formation of the hepatic portal venous system and the hepatic veins, which drain into the inferior vena cava.
Which embryonic structure is the hepatic portal venous system derived from?
the vitelline veins
What is the function of the umbilical arteries and veins?
connection between the intraembryonic and extraembryonic vasculature of the placenta.
Where does the lymphatic system return lymph fluid and cellular compenents?
venous angles of the left and right brachiocephalic veins.
What are the layers of the heart (deep to superficial)?
Endocardium
Myocardium
Epicardium
What 3 layers of the endocardium of the heart?
endothelium, fibroelastic CT, and subendocardium
The endothelium of the endocardium is composed of?
simple, squamous epithelial layer and it’s underlying basement membrane
The fibroelastic layer of the endocardium consists of?
smooth muscle cells scattered though the collagen and elastic fibers
The subendocardium of the endocardium of the heart consists of?
dense CT and, in some regions, myocytes of the heart’s conducting system
What is the myocardium composed of?
contractile cardiac myocytes arranged into fascicles and their investing CT.
What sort of pattern do the myofibers of the myocardium form?
spiraling pattern to surround each chamber.
Which myocarida is thicker, atria or ventricular?
ventricular
What two layers make up the epicardium of the heart?
Subpericardium and visceral pericardium
What does the subpericardium of the epicardium of the heart consist of?
areolar and adipose CT supporting the coronary arteries, cardiac veins, nerves and lymphatic vessels.
What does the visceral pericardium of the epicardium of the heart consist of?
a simple, squamous mesothelium and is continuous with the serous parietal pericardium of the pericardial sac.
Which part of the heart produces the lubricating serous ultrafiltrate contained within the pericardial cavity?
visceral pericardium
What is the cardiac skeleton?
prominent areas of fibrous dense, irregular CT contained mostly within the endocardium and continuous with the perimysium of the myocardium.
What is the function of the cardiac skeleton?
separates the myocardium of the atria and ventricles, forms a part of the interventricular and interatrial septa, and extends into the valve cusps (or leaflets) and chordae tendineae.
What are the 3 major functions of the cardiac skeleton?
a. Electrical insulation between the atria and ventricles to coordinate heartbeat
b. Firm attachment points for the cardiac muscle
c. Anchors and supports all four heart valves
Name the valves, 1-5
- mitral (left AV) valve
- Tricuspid (right AV) valve
- Aortic semilunar valve
- Pulmonary semilunar valve
- AV node (Bundle of His)
What extends from the cusps of the right and left atrioventricular valves and are attached to papillary muscles of the ventricular walls to prevent prolapse of the AV valves during ventricular contractions (systole).
Chordae tendineae
What are the cardica muscle cells called?
myocytes
What are myocytes?
short, blunt cells, with centrally located nucleus, myogenic, contractile cells of the heart
Histology of Cardiac skeleton and valves
How are cardiac muscle cells (myocytes) similar to skeletal muscle cells?
cross-striated appearance (alternating light/ dark bands) due to the organized pattern of the contractile proteins of the myofibrils into sarcomeres.
What are the differences between cardiac and skeletal muscle cells?
greater density of mitochondria, presence of lipid droplets composed of triglycerides, which serve as a reservoir of fatty acids (the main fuel source for cardiac myocytes), and a sparser distribution of sarcoplasmic reticulum which typically only forms a dyad with the Ttubules (rather than triads, as seen in skeletal muscle fibers).
Unique to cardiac muscle, (dark-staining, transverse lines) occur at irregular intervals where two myocytes join in series. They are formed by desmosomes and gap junctions.
intercalated discs
What forms the intercalated discs?
Desmosomes and gap junctions
What are the functions of the desmosome (macula adherens) and fascia adherens (adhering junction) of the intercalated disc of myocytes of the heart?
to tightly bind and anchor the two cell membranes and their cytoskeletons and allow the force to be efficiently transmitted throughout the length of the myofibers.
What do gap junctions of the intercalated discs of the cardiac myocyte provide?
ionic continuity in the cytoplasm of the two cells, allowing synchronized contractions of myocytes within a myofibril.
What surrounds the myofibers of myocytes?
endomysium with a rich capillary network and a thicker perimysium further separates bundles of cardiac myofibers into fascicles
What is atrial natriuretic peptide (or factor) ANP (F)?
membrane-bound vesicles near the nuclear poles of cardiac myocytes (most abundant in myocytes of the right atrium) contain the precursor for ANP.
What is the function of ANP(F)?
Atrial natriuretic peptide functions to decrease blood pressure
In what 2 ways does ANP decrease blood pressure?
vasodilation and antagonizing the renin-angiotensin-aldosterone system (RAAS)
What is the function of the renin-angiotensin-aldosterone system (RAAS)?
— inhibits release of renin (by juxtaglomerular cells), resulting in decreased Na⁺ reabsorption back into the blood. Increased Na⁺ excretion (natriuresis) cause water to follow (diuresis), lowering the blood volume.
Name the parts of the cardiac myocyte? 1-6?
- Z Disc
- Sarcomere
- I band
- A band
- H band
- M line
Where is the precursor for brain-type natriuretic peptide synthesized (BNP)?
Cardiac myocytes in the left ventricle
What is the function of BNP?
vasodilation and antagonizing the renin-angiotensin-aldosterone system (RAAS)
modified cardiac myocytes are specialized to generate and conduct waves of depolarization/hyperpolarization throughout the myocardium and coordinate their rhythmic contractions, resulting in directional force production and blood flow.
Depolarization
What is the difference between conductive and contractile myocytes?
conductive myocytes are larger, have sparsely arranged myofibrils, fewer intercalated discs, and contain more glycogen. They also stain lighter. The 40x slide demonstrates from left to right (endothelium, fibroelastic connective tissue, and subendocardium with large cells with glycogen with Purkinje fibers interspersed.)
Where is the SA node located?
the right atrial wall near the superior vena cava
What is the function of the SA node?
sets the pace and coordinates the simultaneous contraction of the left and right atria,
What structures from the SA node transmit the impulse to the left atrium to synchronize the atrial contractions while internodal bundles transmit the signals to the atrioventricular (AV) node
Interatrial bundles
What structures from the SA node transmit the signals to the atrioventricular (AV) node?
internodal bundles
Where are the AV node AV bundle (of His) located?
the floor of the right atrium near the interatrial septum
What is the function of the AV node?
sets the pace of the ventricular contraction.
What is the function of the AV bundle (of His)?
transmits the impulse through the interventricular septum, which is temporally delayed by the insulating property of the cardiac skeleton. This delay leads to the needed atria and ventricular a synchrony.
What is the course of the AV bundle (of His)?
Within the interventricular septum, the AV bundle splits into left and right bundles that travels toward the apex of the heart and then spreads out into the ventricular walls.
Where are the Purkinje fibers (cardiac)?
within the subendocardial layer (of the endocardium) and intermingle among contractile myocytes of the ventricle and papillary muscles of both the left and right bundles.
What is the function of the cardiac Purkinje fibers?
coordinated wave of ventricular contraction starting at the apex and moving superiorly toward the base, directing the blood flow through their respective outflow vessels and semilunar valves.
Name the structures? 1-7?
- SA node
- Interatrial bundles
- internodal branches
- AV node
- AV bundle (of His)
- Left and right bundles
- Purkinje fibers
CC:
Heart murmur?
regurgitation of blood though a valve
CC:
Angina?
visceral cardiac pain caused by myocardial ischemia
Describe the motor innervation of the heart?
post-ganglionic neurons and axons of the autonomic NS are present in the regions close to the SA and AV nodes.
What does the sympathetic NS do to the heart?
increases pacemaker activity and heart rate
What does parasympathetic stimulation do to the heart?
decreases pacemaker activity and heart rate
Describe the sensory innervation of the heart?
free nerve endings of visceral afferent fibers are distributed throughout the myocardium. Some sensory fibers register pain and discomfort, e.g. angina pectoris, and others relay homeostatic information (not consciously perceived)
What happens to cardiac myocytes under increased load?
increase in size (hypertrophy) in order to generate more force, similar to skeletal muscle fibers.
Cardiac myocytes have little/much regenerative capabilities following injury
little
Why do cardiac myocytes have little regenerative capabilities following injury?
they do not possess satellite cells, as seen in skeletal muscle.
What are the three layers of the blood vessels?
- Tunica intima
- Tunica media
- Tunica externa (adventitia)
What two layers make up the innermost layer of a blood vessel (tunica intima)?
endothelium and subendothelium
Describe the endothelial layer of the tunica intima?
simple, squamous epithelial layer and it’s underlying basement membrane
Describe the subendothelial layer of the internal lining of a blood vessel (tunica interna)?
— loose CT, which may contain scattered smooth muscle cells. In arteries and large veins, a thin internal elastic lamina may be present between the tunica intima and tunica media
Describe the tunica media in blood vessels?
concentric layers of smooth muscle fibers arranged helically. Variable amounts of elastic fibers are interposed between layers of the smooth muscle.
In arteries, a thin external elastic lamina may/may not be present between the tunica media and tunica adventitia?
May
What is the tunica externa (adventitia) composed of?
loose CT composed of type I collagen and elastic fibers that blend in with the CT of the surrounding organs or tissues.
Which of the 3 layers of a blood vessel contain autonomic nerve fibers, mostly sympathetic fibers but in some cases, parasympathetic fibers and Vasa vasorum (“vessels of the vessel”).
Tunica externa (adventitia)
What is the vasa vasorum and where is it located?
(“vessels of the vessel”) are present in the larger and medium sized vessels.
What are the 5 functional roles of endothelium of blood vessels?
- Monitors and mediates the bidirectional exchange of molecules between the blood and surrounding tissues via various mechanisms A. Diffusion B. Transcytosis
- Non-thrombogenic surface and controls local clot formation
- Regulates local vascular tone and blood flow
- Facilitates local inflammation and immune responses
- Promotes proliferation of cells within the vascular wall and white blood cells
Which type of blood vessel has the most effect on systemic BP?
arterioles
How are the arterioles unique?
Endothelium, no connective tissue or smooth muscle
How are capillaries unique?
Endothelium only, exchange metabolites by diffusion
How are venules unique?
endothelium, no valves, drain capillary beds, and site of leukocye extravasation, no tunica adventitia
How arteries a different from veins?
Thicker walls, smaller lumen, tunica media thicker and most prominent layer, no valves.
Which are the elastic (conducting) arteries?
Aorta, pulmonary arteries and their largest branches.
Which type of arteries are the muscular arteries?
Distributing, which are most named arteries other than the elastic arteries (aorta, pulmonary arteries and branches).
What is the smallest artery to supply blood to capillary beds?
arterioles
What vessels are the site of gas and metabolite exchange between blood and tissues?
capilliaries
What are metarterioles?
terminal arterioles (metarterioles), which are continuous with thoroughfare channels that connect to postcapillary venules. From the metarterioles, true capillaries branch off to form the capillary beds and then converge into the thoroughfare channels.
What is the role of precapillary sphincters?
control blood flow into the capillary beds. When the sphincters close, blood flows directly into the thoroughfare channels and into the postcapillary venules.
What is the role of pericytes?
(contractile perivascular mesenchymal cells) are normally associated with capillaries at various locations and form long processes that surround the capillary and may be capable of constricting or dilating the capillaries. Pericytes are capable for proliferating and differentiating into smooth muscles and other cell types.
How do veins differ from arteries?
thinner walls, larger luminal diameter, tunica adventitia usually thicker than tunica media, valves in medium to large veins
Paired valves become present in which size of vein?
medium-sized veins
Valves are an extension of which vessel layer?
tunica intima
What makes up the valve in a vein?
core of elastic-rich subendothelial CT lined by endothelium
What are the three types of microvascular beds?
- Simple pathway (most common).
- Arteriovenous shunt
- Portal system
Which microvascular bed pathway is the most common type?
simple pathway
In which microvascular bed does the vasomotor tone fo the metarterioles regulate perfusion of the capillary bed?
simple pathway
Where are the arteriovenous shunts found?
skin, GI, and skeletal muscles
Which microvascular bed varies blood flow according to external and internal conditions and connect the arterial system to the venous system and allow the blood to bypass the microvascular bed when the shunts are dilated?
Arteriouvenous shunts (anastomoses)
What are some common functions of arteriovenous shunts?
Thermoregulation in the skin, digestion and nutrient absorption with the GI tract, changing skeletal muscle activity.
Which microvascular bed system occurs when one microvascular bed empties into vessels, which then travel to a different region to branch out again into another microvascular bed?
Portal system
Which microvascular bed system allows hormones, nutrients, or other metabolites to be picked up by the blood in the first microvascular bed and delivered more efficiently (faster and at higher concentrations) to the tissue and cells surrounding the second microvascular bed, before the blood is returned to the heart for general distribution throughout the body?
The portal system
Two examples of porta systems in the body are:
Hepatic portal system — a venous portal system (largest and most well-known)
Hypophyseal portal system — a venous portal system
Capillaries are group into which 3 major types?
Continuous, fenestrated, discontiuous (sinusoidal).
Which type of capillary is the most common and the most restrictive?
Continuous
Where can you find continuous capillaries?
Muscle, CT, lungs, exocrine glands, and nervous tissue
Describe the endothelial cells character of continuous capillaries?
Overlapping, tight occluding junctions to prevent paracellular transport and minimize fluid leakage, basement membrane forms a uniform underlying sheet.
Which type of capillary is found in organs and glands that require a more extensive and rapid exchange of substances between the blood and tissues?
Fenestrated
Where are the fenestrate capillaries located?
Glomeruli (kidneys), intestines, choroid plexus, most endocrine glands
Which type of capillaries have endothelial cells that are penetrated by numerous small opening (fenestrations)?
Fenestrated
Which type of capillaries occur in organs and glands that require the movement of cells and a large range of macromolecules and substances across the endothelium?
Discontinous (sinusoidal)
Where are the discontinuous (sinusoidal) capillaries found in the body?
Present in liver, spleen, bone marrow and some endocrine organs
Which type of capillaries have endothelial cells that have larger perforations that lack any diaphragms with several intercellular clefts (open space between adjacent cells), creating a discontinuous endothelium. • Basement membrane is also highly discontinuous with large opening.
Discontinuous (sinusoidal)
What are the specialized arterial sensory structures?
Carotid sinus and carotid body
What is the function of the carotid body?
Baroreceptors within the arterial wall monitor arterial blood pressure. Sensory nerve ending in the area (primarily CN IX, but may include CN X) transmit those signals to the appropriate nuclei of the brainstem that modulate cardiac, respiratory, and vasomotor activities.
What is the function of the carotid body?
possess a complex of chemoreceptors monitoring blood O2, CO2, and H⁺ levels. Neurotransmitters are released primarily in response to hypoxia (low O2); however, hypercapnia (elevated CO2) or acidosis (elevated H⁺) can also stimulate their release.
