Card Set Information
Basic organization of CV components
ALL components of the CV system have 3 layers
1. Tunica intima (inner, endocardium)
2. Tunica media (middle, myocardium)
3. Tunica adventitia (outer, epicardium)
Lumenal (inner) layer
Endothelium (simple squam.) contacts blood
Subendothelium (loose CT / some smooth m. cells)
How is the tunica intima oriented?
endothelium / subendothelial elements arranged on the axis of blood flow
Functions of endothelium
1. Maintains selective permeability barrier.
2. Maintains non-thrombogenic barrier.
3. Modulates blood flow and vascular resistance.
4. Regulates cell growth.
5. Regulates immune response.
6. Maintains ECM.
7. Involved in lipoprotein metabolism
Most prominent layer in arteries
- Smooth muscle / Elastic membranes (concentric / relative)
- Reticular fibers (type III collagen)
How are elements of the tunica media oriented
Elements of media are oriented
(smooth muscle / elastic membranes)
What synthesizes all the ECM in the tunica media?
ECM made by
smooth muscle cells
Predominant feature of elastic arteries?
Where is it found?
What does it do?
Elastic lamellae (type III reticular fibers / proteoglycans)
Found in the tunica media
Elastin rebound maintains BP in diastole (relaxation)
What separates the t. intima and t. media?
Internal elastic lamina
(both; prominent in muscular arteries)
What separates the t. media and t. adventitia?
External elastic lamina
Most prominent layers in veins
Connective tissue sheath
- mainly type I collagen
- elastic fibers
- smooth muscle
Vasomotor nervi vascularis
- innervated smooth m. of
large vessels may have vasa vasorum
Where are vasa vasorum found? Be specific
Vasa vasorum found in t. adventitia of large blood vessels
How are elements of the tunica adventitia oriented
t. adventitia is oriented
Basic organization of heart tissue
4. Conducting system of specialized cardiac m. cells
Innermost heart layer (analog = t. intima)
Underlying layer of the endocardium
Composed of loose CT / elastic fibers / some smooth m. cells
Contains small veins / nerves
In some locations, also contains Purkinje fibers
Specialized cardiac muscle cells (subendocardium)
- larger than reg. cardiac m. cells
- fewer myofibrils (stains lighter)
- central nucleus (often binucleated) surrounded by glycogen (light area)
Conduction system of the heart
- Impulse initiated at SA node (pacemaker)
- Travels to AV node
- AV bundle (of His) sends impulse to L/R bundle branches to apex of heart.
Middle heart layer (analog = t. media)
- Thicker in ventricles (inner circular / outer spiral layers)
- Cardiac m. is anchored to cardiac skeleton (dense fibrous CT)
- Cardiac m is postmitotic
Histological changes in myocardial infarcted tissue
- Lots of inflammatory cells
- Necrotic tissue
With time, inflammatory cells increase in number / lots of scar tissue
Outermost heart layer (analog = T. Adventitia)
- Thick layer of loose CT / adipose
- Contains neurovasculature
- Outermost layer = mesothelium (simple. squam)
- forms visceral serous pericardium
1. Right AV (tricuspid)
2. Left AV (mitral)
- endothelial cells rest on thick subendothelium
- longitudinal oriented CT
- internal elastic lamina not clearly defined
- concentric lamellae of elastin (40-70)
- some smooth muscle
- thin, compared to vessel
- vasa vasorum, extend into t. media
- endothelial cells rest on subendothelium (some smooth m.)
- longitudinal orientation
- internal elastic lamina, prominent identifying feature
- concentric smooth muscle (3-40)
- some elastin (special stain required)
- external elastic lamina
- longitudinal oriented fibroblasts / collagen / elastic fibers
- vasa vasorum / lymphatics
- endothelial cells rest on
- internal elastic lamina not usually visible
- concentric smooth muscle (< 3)
- very thin
- Continuous endothelium resting on basal lamina
- Cells joined by tight junctions (zonula occludens)
- Found in CNS / PNS, muscle, CT, exocine glands
What is special about CNS capillaries?
Surrounding basal lamina of continuous capillaries is layer of astrocytic endfeet. Endfeet induce formation of blood-brain barrier
- endothelial tight junctions
- paucity of pinocytotic vesicles
- Continuous endothelium interrupted by pores (fenestrae)
- Pores may have thin diaphragm over them (except renal glomeruli)
Endocrine vs. Exocrine capillaries
Endocrine = fenestrated
Exocrine = continuous
- Specialized w/ relatively large lumens
- Many open fenestrations
- Absence of continuous basal lamina
- Macrophages present along walls
Found in liver / lymphoid / hematopoietic organs
- small, postcapillary vessels
- paired w/ arterioles
- very thin walls
- functional characteristics of capillaries (exchange vessels)
- very thin
- valves formed by subendothelial CT (not in large veins)
- valves have covering of endothelium
= poorly developed
= very well developed
What are the prominent layers in arteries vs. veins?
Artery = prominent media
Vein = prominent adventitia
Large arteries vs. Large veins
- thick intima
- thick media
- underdeveloped adventitia
- thick intima
- thin media
- well developed adventitia w/ longitudinal bundles of smooth m.
- very thin-walled vessels
- large irregular lumens (some valves)
- larger lymphatics similar to veins w/o well defined tunics
Should not see RBC's in lymphatics