Cardiac Muscle Like Skeletal Muscle is ______
Striated
Do cardiomyocytes normally branch
Yes
How many nuclei are associate with each cardiomyocyte?
One or two
Cardiomyocyte nuclei are located ________ within the fibers.
Centrally
Identify the intercalated disks between cardiomyocytes
If you were to examine intercalated disks ultrastructurally, what two major cell/cell junctions would you find?
- Fascia adherens - in the transverse part
- Gap Junctions - in the lateral part
What is the functional significance of intercalated disks?
The components of intercalated disks enable cell adhesion and electrical coupling of adjacent cardiomyocytes.
The cross sectional diameter of cardiomyocytes is ______. Why?
The cross sectional diameter of cardiomyocytes is variable, because cardiomyocytes branch.
What morphological features would you look for as evidence of a previous myocardial infarction (MI)?
You would see an accumulation of collagen indicative of scar formation.
What does the circulatory system include?
The cardiovascular system and the lymphatic system.
What do tissues do blood vessels contain?
1) epithelium, which in blood vessels is termed endothelium
2) connective tissue, which is found in all 3 blood vessels tunicas. (intima, media and adventitia)
3) muscle, specifically smooth muscle
What are some of the fucntions of the circulatory system?
1) Transportation of O2, nutrients, waste products, body fluid, solutes, and immune system components.
2) Facilitate body heat homeostasis
Tunica intima
Boaders the Lumen
Consist of endothelium (simple squamous epithelium) and subendothelial connective tissue.
What can sometimes be found inbetween the tunica intima and tunica media?
Internal elastic lamina
Tunica Media
Consists of vascular smooth muscle arranged in concentric layers along with fenestrated elastic laminae.
What seperates the tunica media from the tunica adventitia in large arteries?
External elastic lamina
Tunica Adventitia
The outermost layer of the vessel wall.
The fenestrated elastic laminae
fenestra - means window
they are sheets of elastic fibers wrapped around the vessel lumen. Within these elastic sheets are fenestra/windows.
In the light microscope what does elastic fibers look like?
They appear shiny or refractile, which is most evident when the sub-stage (iris) diaphragm is partially closed.
What is the functional significance of the fenestrated elastic laminae in the elastic artery?
The elastic tissue in elastic arteries helps maintain constant arterial pressure by stretching during ventricular contraction (systole) and recoiiling during ventricular relaxation (diastole).
The nuclei within the tunica media belong to what cell type?
Smooth muscle cells
In a muscular artery
The sub-endothelia CT of the intima is relatively thick.
The tunica media is quite thick in this type of cessel.
Fenestrated elastic laminae are less prominent than when present in the elastic artery.
What is the function of the vasa vasorum?
Provide O2 and nutrients to cells within the tunica media of large vessels, particularly veins which obtain less O2 by diffusion from the blood due to the O2 poor quality of the blood they transport.
What does A refer to?
What does B refer to?
A = Internal Elastic Lamina
B = External Elastic Lamina
The number of coronary artery bypass procedures has declined recently. Which procedure involving coronary artery lumen enlargement is used by cardiologists?
angioplasty (percutaneous transluminal coronary angioplasty (PTCA))
What are some possible interventions to promote endothelialization?
1) Local administration of endothelial cell growth factors (e.g. VEGF)
2) Endothelial cell seeding
3) Estrogen-loaded stents - promote healing and reduce SMC migration and proliferation- stes which attract circulating endothelial cells.
What is an arteriole characterized by?
- an external diameter less than 100 micrometers (~15 RBCs in diameter from adventitia to adventitia)
- wall thickness that is approximately equal to lumen diameter
- little or no dubendothelial connective tissue
- 2 to 5 smooth muscle layers in the tunica media
- no external elastic lamina
- very thin tunica adventitia
What do metarterioles do?
Regulate blood flow from arterioles into capillary beds due to its precapillary sphincters.
Capilaries
7 micrometers in diameter
Which allows only a single RBC to pass.
consist of only endothelial cells.
(Nucleus is not always in the same plane of the section)
Continuous capillaries
Cardiac and Skeletal Muscle, brain and peripheral nerves
The endothelial cells are tightly attached to each other by junctional complexes
Fenesstrated capillaries
Found in the kidneys, intestine and some endocrine glands where rapid exchange occurs between the blood and other tissues.
Have pores (fenestrae/fenestrations) within the endothelial cell cytoplasm.
Sinusoidal Capillaries
Found in bone marrow, liver, lymphoid organs and some endocrine glands.
Have unusually wide lumens (30-40 micrometers), fenestrations, gaps between the endothelial cells of their walls and a discontinuous basal lamina outside of the endothelial cells.
Shape is tortuous because it conforms to the channel created by the parenchymal cells of the surrounding tissue.