Histology Flashcards
What are the functions of the cardiovascular system?
1) Transport oxygen and nutrients to tissues
2) Transport carbon dioxide and metabolic waste from the tissues
3) Regulate temperature
4) Distribute hormones and immune cells
5) Reproductive function in males- pinile erection
Where is the blood found at rest?
65% peripheral veins, 20% in heart and lungs, 10% inn peripheral arteries and 5% in capillaries
What are the 3 layers of any blood vessel?
1) Tunica intima
2) Tunica media
3) Tunica adventicia
What composes the tunica intima?
A single layer of squamous epithilial cells (endothilium) with a basal lamina and thin layer of connective tissue
What comprises the tunica media?
Predominantly of smooth muscle cells
What comprises the tunica adventicia?
Connective tissue blending with surrounding connective tissue
What separates the 3 layers of the vessel wall?
Elastic membranes which have perforations
1) Internal elastic membrane
2) External elastic membranes
Name some elastic arteries?
Aorta and pulmonary arteries
What makes elastic arteries unique?
Some of the smooth muscle in the media is replaced by elastic fibres providing elastic recoil to maintain a diastolic BP
How do large arteries obtain oxygen and nutrients?
The vessels have a vascular supply in the tunica adventicia: Vasa Vasorum
What are the characteristics of an arteriole?
1-2 layers of smooth muscle in the tunica media and almost no adventicia. Diameter of 30-200 microns
What are the characteristics of capillaries?
Single layer of epithilial cells and a basal lamina. Diameter of 4-8 microns. Often have pericytes just outside the basel lamina
What are pericytes?
Connective tissue cells with contractile properties
What are the 3 types of capillary?
Continuous
Fenistrated- 50nm pores in the wall
Sinusoidal/discontinuous- no basal lamina and large gaps in which marcomolocules can pass through
Where are continuous capillaries found?
Muscle, connective tissue, lung, skin and nerves
Where are fenistrated capillaries found?
Gut, endocrine glands, glomeruli of kidney
Where are discontinuous capillaries found?
Liver, spleen and bone marrow
How do small arterioles connect to post capillary venules?
Through the mircovasculature- a network of metarterioles, thoroughfare channels and capillaries
What is the function of a thoroughfare channel?
To shunt blood from the arteriole to the venous side
What are pre-capillary sphincters?
Smooth muscle sphincters at the beginning of the capillary which help control the flow through the network
What are the characteristics of a post capillary venule?
10-30 microns. Endothilial cells lined with a thin layer of connective tissue and occasional pericytes.
Site of exchange of inflammatory molecules
What are the characteristics of venuoles?
> 50 microns with intermittent smooth muscle cells in a tunica media
What are the characteristics of veins?
Have a tunica intima, thin but continuous tunica media.
The largest veins have a thick tunica adventicia which incorporates bundles of longitudinal smooth muscle
Valves which are the extensions of the tunica intima
What are the 3 layers of the heart?
Endocardium, Myocardium and Epicardium