Histology Flashcards
Histologically classify the fibrous skeleton of the heart
Dense Irregular CT
What is the function of the fibrous skeleton?
Place for valves to attach
Extends into interventricular septum
Acts as electrical insulator to prevent flow of action potential from atria to ventricles (forces conduction through AV node)
Impulse conduction system of the heart is made up from what type of cell?
Muscle cell
What are the 3 layers of the heart wall?
Epi, Myo, and Endocardium
Histologically classify epicardium
(Mesothelia) - Simple Squamous Epithelium
Histologically classify endocardium
Simple Squamous Epithelium
What are 4 histological differences between skeletal muscle and cardiac muscle?
Cardiac muscle has 1 centrally located nucleus
Intercalated discs
Diads (not triads)
More mitochondria and other organelles
Histologically classify Purkinje fibers
Modified cardial muscle fibers
What are the 3 layers of vessel walls?
Tunica Intima
Tunica Media
Tunica Adventitia
What comprises the tunica intima?
Endothelium
Subendothelium Loose CT
fenestrated Internal Elastic Lamina (arteries and arterioles only)
What comprises the tunica media?
Circumferentially arranged smooth muscle fibers
(Arteries have interal and external elastic fiber layers)
What comprises the tunica adventitia?
Longintudinally arranged CT and elastic fibers
(Vaso vasorum and nervi vascularis in large vessels)
(smooth muscle in thick veins)
How can you recognize a vein by its tunica?
Vein will have much larger tunica adventitia
Describe a large elastic artery like the aorta
Thick tunica intima
Thick tunica media with lots of elastic fibers
Thick tunica adventitia with vasa vasorum and nervi vascularis
Describe a muscular artery
Thinner tunica intima than elastic artery
Prominent internal elastic lamina
Thick tunica media
What is a good reference point for telling the size of an artery
If it has clear internal elastic lamina then considered muscular or elastic
Describe arterioles
Have small tunica media layer compared to other arteries
No internal elastic lamina
Thin tunica adventitia and thin tunica intima
Describe a capillary
About diameter of a red blood cell
**Usually only has tunica intima **
(Maybe has pericyte tunica media)
Define a pericyte
CT cell similar to mesenchymal cell
Contractile
May help with would healing
What are 3 types of capillaries?
Continuous
Fenestrated
Sinusoidal
Describe a continuous capillary
Has pinocytotic vesicles
Has tight junctions
Located in muscle, fat, lung, CNS
Describe a fenestrated capillary
Has pinocytotic vessels
May have diaphragms
Found in endocrine glands, kidney, and GI
Describe sinusoidal capillary
Large lumen diameter
Gaping spaces between endothelial cells
Incomplete basal lamina
In spleen, liver, and bone marrow
Describe arteriovenous anastomoses
Shunt past capillary - from arteriole to venule
Active organ has closed shunts so blood must go through capillary and provide oxygen
Organ at rest opens AV shunts
Describe metarterioles
Main highway between capillary
Precapillary sphincters can divert blood to highway or local roads
How to generally recognize veins against arteries?
Veins have large lumen, thin walls, irregular shape
From which blood vessels do WBCs choose to extravate into tissue?
From post-capillary venules
How do you discern a venule from a small/medium vein?
Veins have smooth muscle, elastic fibers, collagen fibers,
How do you discern large and small veins?
Large veins have 2 layers of smooth muscle - both longitudinally and circumfrentially
Small veins only have one layer in tunica media
Continue with lymphatics
