Cardiovascular System I Flashcards
What is the outer layer of the heart made of?
Epicardium
simple squamous epithelium
subepicardial connective tissue containing:
blood vessels, fat, nervous tissue
What is the myocardium? What is it comprised of?
Middle layer of the heart
muscle cells and capillaries
Where is the endocardium? What is it?
Inner layer of the heart
squamous epithelium/endothelial layer, subendocardial CT, conducting tissue
What cell type is this?
Cadiac muscle
small cells
central nuclei
branching, long fibres joined end-to-end
intercalated discs
ID is
intercalated disc
anchors actin filaments of sarcomeres to neighbouring sarcomeres via fascia adherens (desmosomes)
gap juctions run in the perpendicular join between IDs
Purkinje fibres
larger than muscle cells
limited non-functional myofibrils (tf light pink H&E)
full of glycogen
in subendocardium (beneath endocardium lining the lumen of the heart)
The intima of blood vessels is lined with
simple sqamous epitheliym (e.g. the endothelium) on a basal lamina supported by a thin subendothelial CT layer
The connective tissue of the media is secreted by the _________________ and contains?
Smooth muscle
collagen III, elastin, and ground substance
What comprises the connective tissue of the adventitia?
Collagen I, elastin, ground substance
plus embedded fibroblasts
What is the vasa vasorum?
Blood vessels that supply larger blood vessels with nutrients and oxygen
What type of arteries are the aorta and the carotids?
Elastic
~50 layers of elastin between the smooth muscle cells
What does diastolic pressure reflect?
Elastic recoil of the arteries near the heart transferring energy into blood to push it through arteries
What is the main role of muscular arteries?
Regulating pressure
What is the diameter of an arteriole?
<0.1mm
Where is the greatest resistance to flow?
Arterioles
What are the primary regualtory vessels of blood pressure?
arterioles
What is the metarteriole?
the metarteriole is between the arteriole and the capillary bed
single muscle cells act as sphincters to control capillary flow
What are the structural features of the capillary?
- single endothelial cell rolled into a tube
- sealed with a tight junction
- basal lamina, barrier to diffusion (dense layer of CT)
- no media; some pericytes
- few collagen fibres (adventitia merged to ground substance of extracellular space)
What percentage of blood is in the veins?
70%
70% of blood is in the
veins
How does venous structure differ from arteries?
- thinner media
- thicker adventitia (to withstand hydrostatic pressure)
- one-way valves
What are the characteristics of venules?
- first level of venous collection
- media initially pericytes, eventually smooth muscle
- preferred site of diapedesis
- affected by histamine, cytokines
- look similar to arterioles but larger diamater due to lower P (must carry same volume)
Relative to arteries, medium to large veins have:
- more subendothelial CT than arteries
- thicker adventitia (+CT), thinner media (-muscle)
- longitudinal SM in adventitia to prevent buldging
- larger diameter
Lymphatic vessels drain
plasma/fluid leaked out from capillaries and venules into the extracellular space
What is the =difference between a lymphatic vessel and a vein or capillary?
No gap junction between ends of the endothelial cell tf leaky so plasma and fluid can get in
No RBCs in lumen
thinL no media/muscle! just CT and endo
