Histology Flashcards
(31 cards)
What are the roles of the cardiovascular system
Transport of oxygen and nutrients to the tissues.
Transport of CO2 and other metabolic waste from the tissues.
Temperature regulation.
Distribution of hormones and immune cells.
Reproductive function in males: penile erection.
Where is the majority of blood found at any one time
Peripheral veins
around 65% is found here
Describe the basic 3 layer structure of blood vessels
Inner layer: Tunica intima, a single layer of squamous epithelial cells called endothelial cells supported by a basal lamina and a thin layer of connective tissue.
Middle layer: Tunica media, made up predominately of smooth muscle. Thickness varies tremendously
Outer layer: Tunica adventitia, made up of supporting connective tissue.
How are the 3 layers of blood vessels separated
Intima separated from media by layer of elastic tissue called the internal elastic membrane.
Media separated from adventitia by layer of elastic tissue called the external elastic membrane
What is meant by the term ‘elastic arteries’
Term applied to the largest arteries as they have many sheets of elastic fibres in their tunica media to provide elastic recoil
What is the vasa vasorum
The vessels that supply blood to the largest blood vessels
When does an artery become an arteriole
When layer of smooth muscle gets down to only one or two layers,
Describe the structure of arterioles
Have only one or two layers of smooth muscle in their tunica media
Almost no adventitia
They are particularly important in controlling blood flow in a tissue
Describe the structure of capillaries
Essentially composed of endothelial cells and a basal lamina
Gives the smallest distance between oxygenated blood and the cells that need it
Often have pericytes at intervals just outside the basal lamina. These are connective tissue cells with contractile properties
What are the 3 types of capillary
Continuous
Fenestrated
Sinusoidal or Discontinuous
Describe continuous capillaries
The most common
No pores in capillary wall
Found: muscle, connective tissue, lung, skin, nerve.
Describe fenestrated capillaries
have ~50nm pores in wall
Found: mucosa of the gut, endocrine glands, glomeruli of the kidney
Describe sinusoidal or discontinuous capillaries
lack a basal lamina and have large gaps through which macromolecules, and in some cases even cells, can pass
Found: liver, spleen and bone marrow.
Describe the microvascular network
Small arterioles connect to a postcapillary venule through a network made up of metarterioles (smallest vessel just before the capillary), thoroughfare channels and capillaries.
What are precapillary sphincters
Composed of smooth muscle
Found at the beginning of the capillary
Help control flow through the microvascular network
Describe the structure and function of into post-capillary venules
Capillaries drain into them
Important sites for exchange
They are endothelial cell-lined and contain a thin layer of connective tissue and occasional pericytes
When do the post-capillary venules become referred to as venules
Once the vessel begins to acquire intermittent smooth muscle cells in a tunica media layer
Describe the structure of veins
Tunica intima
Relatively thin but continuous tunica media - made up of few layers of smooth muscle
The don’t need many layers of muscle as blood is at low pressure
Largest veins have smooth muscle in the adventitia
Most have valves that are inward extensions of the tunica intima
What are the 3 layers of the heart
Endocardium: inner layer
Myocardium: middle layer
Epicardium: outer layer
Describe the structure and function of the endocardium
Lines the entire inner surface of the heart
Structure: endothelium, basal lamina, thin layer of collagen fibres, layer of denser connective tissue
Some areas have a subendocardium of loose connective tissue containing small blood vessels and nerves
Describe the structure of the myocardium
Thick middle layer
Has bundles and layers of contractile cardiac muscle fibres.
Individual muscle fibres are surrounded by collagenous connective tissue with a network of capillaries.
What is the function of the intercalated discs between cardiac muscle cells
They bolt the cells together (end to end) so that they don’t pull apart on contraction
Describe the structure of the epicardium
On the surface of the heart: A single layer of flattened epithelium called mesothelium.
Basal lamina Fibroelastic connective tissue and, in some places, adipose tissue.
What are the 2 parts of the pericardium
The fibrous pericardium
The serous pericardium
