Histology Flashcards
two types of circulation
pulmonary and systemic
blood vessels
Arteries carry blood to peripheral capillary beds
Veins carry blood from peripheral capillary beds to heart
Capillaries are the site of exchange
*Sometimes there are veins or arteries in-between two capillary networks (“portals”)
two septa
interatrial, inerventricular
4 chambers
4 chambers
Right Atrium
Receives blood via inferior and superior venae cavae
Right Ventricle
Receives blood from right atrium ,pumps to lungs via pulmonary arteries (deoxygenated)
Left Atrium
Receives oxygenated blood from lungs via pulmonary veins
Left Ventricle
Receives blood from left atrium, pumps into aorta for distribution through body
portal examples
hepatic and the one in the pituitary gland
myocardial building blocks
cardiomyocytes. Thicker in the ventricles than in the atria.
Fibrous skeleton of heart: structure
Dense, irregular connective tissue Part of 2 septa Surrounds valves Encircles aorta and pulmonary trunk Chordae tendinae
Fibrous skeleton of the heart: function
Anchors and supports valves
Provides insertion for cardiac muscle
Electrical insulation between atria and ventricles
chordae tendinae
heartstrings. open and close valves.
Conducting system of heart: function
Depolarizes heart, allows for rhythmic contractions
SA Node: cell features and location
Nodal cardiac muscle cells
Smaller than other cardiomyocytes, no intercalated discs
Near junction of Superior vena cava and right atrium
Fastest depolarization
AV Node: cell features and location
Nodal cardiac muscle cells
Smaller than other cardiomyocytes, no intercalated discs
Picks up electrical signal from SA Node, sends through bundle of His
Second fastest depolarization
Purkinje fibers
Modified cardiomyocytes
Lots of glyocgen
3rd fastest depolarization
NOT located in myocardium
Coronary vasculature
Coronary vasculature
Left and right coronary arteries, originate from ascending aorta, branches converge toward apex
Many coronary veins, drain into coronary sinus, which drains into the right atrium
Pericardium
fibrous sac, attaches to diaphragm and organs
Epicardium
Adheres to outer surface of heart
Single layer of mesothelium
Squamous
Provide slippery surface
Adipose and loose connective tissue
2 layers: visceral and parietal serous pericardium
Potential space, site of cardiac tamponade
Nerves and ganglia travel through this layer
four layers of heart
Pericardium, epicardium, myocardium, endocardium
another word for epicardium
serous layer of pericardium
layers of pericardium
parietal and fibrous
cardiac muscle: properties of the sarcomere
striations and intercalated discs, branching (allows for communication)
intercalated discs of myocytes
stair-step connections between myofibers/myocytes
Instead of z-lines
what type of cardiomyocyte doesn’t have intercalated discs?
the nodal ones
nuclei of cardiomyocytes
one, maybe two per. Located in the middle.
adhesive functions of intercalated discs
Fascia Adherens
Most extensive
Bind actin (like a Z-band)
Desmosomes (Macula adherens)
Anchor to intermediate filaments of the cytoskeleton, hyper-adhesive
Gap junctions
Open pores = continuous connection between two cells
cardiac muscle vs skeletal muscle
Most of accessory proteins similar, use actin and myosin as contractile units Troponin used as sign for MI T-Tubules are close to Z-lines, NOT A-I junctions 1 T-Tubule + 1 Terminal Cistern = diad More of these in ventricles than atria SR is less organized RYR2 is isoform Calcium-gated calcium channel
Endocardium
Inner layer: Endothelium and loose connective tissue (elastin and collagen)
Middle layer: Smooth muscle and connective tissue (elastic)
Subendocardial layer: Connective tissue and Conduction system of heart, Nodes, Bundle, Purkinje
Smooth muscle organization
Elongated, tapering, NON-striated Not structured in sarcomeres Spontaneous contractile activity Single nucleus Sarcomeres not organized around z-bands, instead Dense bodies Myogenic Also contract to paracrine factors
smooth muscle myosin arrangement
“side-polar;” looks more like rows of hooks, skeletal muscle looks like leaves or flowers on a vine
Endocardial composition of heart valves
Fibrosa: Continuation of rings, Dense, irregular connective tissue
Spongiosa: Shock absorption, Loose connective tissue
Arterialis or Auricularis
Ventricularis: Adjacent to ventricular or atrial valve surface, Endothelium, Dense, connective tissue, Continuous with chordae tendinae
Autonomic nervous system impacts on heart
tachycardia (norepinephrine– beta blockers block these receptors), bradycardia (ach).
3 reflexive receptors that regulate the heart rate
baroreceptors in the carotid sinus and aortic arch, pressure receptor within the atrial and ventricular walls, (tilt table test) chemoreceptors measure pH in the carotid and aortic bodies. (wake up in the night!)
major cranial nerves related to cardiac stuff
9 and 10
Nucleus of the solitary tract
important!! heart receptors send afferent signals here to work changes in heart rate.
Glomus cell
found in carotid bodies, detects pH changes from CO2 –> signals to nucleus of solitary tract
layers of blood vessels
Tunica intima, tunica media, tunica externa. continuous with layers of heart.
vein vs. artery
vein: valves, larger lumen, smaller tunica media. Walls have more collagen.
Arteries: wall is thicker, contains more smooth muscle and elastic fibers, always has inner elastic layer.
Medium-sized veins and muscular arteries usually travel together.
distinctions between layers are less clear in veins
sizes of veins and arteries
Large veins, elastic arteries
medium-sized veins, muscular arteries
Venules, arterioles
Tunica intima
continuous with endocardium. Endothelium around lumen Basement membrane Subendothelial connective tissue Inner Elastic Lamina
Tunica media
continuous with myocardium. Tunica media (myocardium) Mostly smooth muscle External elastic lamina Thickest in arteries
What vessel doesn’t have a basement membrane?
lymphatic
Tunica adventitia
continuous with epicardium. Mostly dense connective tissue Lots of fibroblasts Vasa vasorum Nervi vasorum (both GVA and GVE) Thickest in veins
Elastic artery aspects
relatively thic intima, IEL is not conspicuous, lots of elastic laminae in media, thick media, collagen, elastin in adventitia to prevent overdistension, most nervi and vasa vasorum
muscular artery aspects
thinner intima, IEL is conspicuous, very little elastic laminae in media, thick media, thicker adventitia, may see external elastic membrane (EEL)
Precapillary sphincters
control blood pressure to capillaries
myocardial sleeve
extension of myocardium in adventitia. Not sure what it does. In excess, it means there is some type of heart problem– often atrial fibrillation.
characteristics of arteriole
very thin tunica intima, IEL not distinct, 1-5 layers of smooth muscle, EEL not visible, very thin adventitia, can contain precapillary sphincters.
Large veins
tunic intima and media aren’t clearly separated. IEL is not conspicuous. Thick adventitia, may contain smooth muscle. Extensions of myocardium in adventitia = myocardial sleeves
Medium-sized veins
valves common (from intima). DVTs common here, similar organization to large veins, less smooth muscle in adventitia
Properties of the endothelium in blood vessels
selectively permeable barrier (pinocytosis common and clathrin dependent) produces anticoagulants (but damage promotes thrombogenesis) secretes vasodilators and vasoconstrictors secretes growth factors modifies lipoproteins (macrophages convert these to foam cells)
characteristics of capillaries
1 layer of endothelial cells Thinner than erythrocytes Allows for diffusion of nutrients and gasses Basal lamina Surrounded by pericytes
pericytes
undifferentiated mesenchymal stem cells
three types of capillaries
continuous, fenestrated, discontinuous
continuous capillaries
most common, basal lamina is continuous, endothelium uninterrupted, tight junctions
fenestratd capillaries
around glands and sties of absorption. basal lamina is continuous. endothelium has perforations
discontinuous capillary
irregularly shaped, liver, spleen and marrow. discontinuous basal lamina. endothelium has large perforations.
microvascular bed and shunting
in arterioles and metarterioles with precapillary sphincters, blood can be shunted away from capillary bed. Used in thermoregulation, reason our hands get “pruny”
lymphatic vessels
Unidirectional flow of lymph
Smallest are capillaries, converge into lymphatic vessesls
Largest vessels are thoracic duct, right lymphatic trunk
Irregular lumen diameter
Lymphatic walls are thin
Poorly developed adventitia
Have smooth muscle in media
Lymphatic capillaries lack basal lamina, pericytes
Anchored to perivascular collagen by Anchoring filaments
