Histology Flashcards
Where is the sinoatrial node found?
Junction of the superior vena cava and the right atrium
Describe the features of cardiac muscle
Cells are striated
One centrally placed nucleus
Specialised functions called intercalated discs which also act as Z lines
Have gap junctions for cell to cell communication
Name some elastic arteries
Pulmonary Aorta Brachiocephalic Subclavian Carotid Common iliac
What are the blood pressures during systole and diastole of the elastic arteries?
Systole: 120mmHg
Diastole: 70-80mmHg
What is in the tunica media?
External elastic lamina
Elastic membranes
Smooth muscle cells
Collagen
Describe the walls of arterioles
1-3 layers of smooth muscle cells in the tunica media
Only larger ones have a thin, elastic lamina
External elastic lamina is absent
Tunica adventitia is scant
Which arteries arise from the aorta?
The brachiocephalic, common carotid and left subclavian
What does the aorta bifurcate into in the abdomen?
The left and right common iliac arteries
How much blood does the CVS need to deliver to tissues?
5-25L/min
What blood flow does the brain require?
0.75L/minute
How is flow contolled?
Arterioles and pre-capillary sphincters
What is the blood volume?
5L
How much blood is in arteries and arterioles?
0.55L
How much blood is in capillaries?
0.25L
How much blood is in veins?
3.35L
How much blood is in the heart and lungs?
0.85L
What is the function of arterioles?
Regulate amount of blood reaching tissues
Regulate blood pressure
What type of arteries are arterioles
Muscular
How high is blood velocity in capillaries? Why?
At its lowest
Allows time for exchange with surrounding tissues
Diameter of capillaries?
Length of capillaries?
7-10 μm
Less than 1mm
Describe continuous endothelial layer
Cells joined by tight/occluding junctions
Where are capillaries with continuous endothelium found?
Nervous, muscle and connective tissues
Describe fenestrated endothelium in capillaries
Has interruptions in the endothelium and bridged by a thin diaphragm.
Where is fenestrated endothelium found?
Gut, endocrine glands and the renal glomerulus
Describe sinusoidal endothelium
Larger diameter (30-40 μm) and slower blood flow. Gaps exist in the walls allowing whole cells to move between blood and tissue.
Where are sinusoidal capillaries found?
Liver
Spleen
Bone marrow
What are pericytes?
Form a branching network on outer surface of endothelium
Can divide into muscle cells or fibroblasts during angiogenesis, tumour growth or wound healing
Which veins do not have semi lunar valves?
Those less than 1mm in diameter
Those found in the thoracic and abdominal cavities
Characteristics of the tunica intima in elastic arteries?
Endothelial cells with long axes parallel to the long axis of the artery
Narrow sub-endothelium of connective tissue with discontinuous internal elastic lamina
Features of the tunica media of elastic arteries?
40-70 fenestrated elastic membranes
Smooth muscle cells and collagen between these lamellae
Thin external elastic lamina may be present
What is in the tunica adventitia of muscular and elastic arteries?
Vaso vasorum
Fibroelastic connective tissue
Lymphatic vessels
Nerve fibres
Features of tunica intima of muscular arteries?
Endothelium
Sub endothelial layer
Thick internal elastic lamina
Features of tunica media of muscular arteries?
40 layers of smooth muscle cells connected by gap junctions for coordinated contraction
Prominent external elastic lamina
What type of nerve fibres stimulate vasoconstriction? What is the neurotransmitter?
Sympathetic
Noradrenaline
When is an artery considered to be an arteriole?
When its diameter is less than 0.1 mm
How many layers of smooth muscle cells do arterioles have?
1-3
What is a pre-capillary sphincter?
A smooth muscle cell that encircles the endothelium of a capillary arising from a metarteriole
What is re permeability of post capillary venules compared to capillaries?
More permeable
Which way does fluid flow in a post capillary venule? ie out of or into the vessel through the wall?
Fluid tends to drain in, due to low pressure
Diameter of venules?
Up to 1mm
How do veins compare to their accompanying artery?
Larger diameter
Thinner wall with more connective tissue and fewer elastic and muscle fibres
What is the order of vessels that blood passes through?
Large arteries (elastic) Medium arteries (muscular) Arterioles Metarterioles Capillaries Post capillary venules Venules Medium veins Large veins
What is found in the tunica adventitia of arteries?
Thin layer of fibrous connective tissue
Vaso vasorum
Lymphatic vessels
Nerve fibres
