Histology 4 (Blood Vessels And Nerves) Flashcards
What is the lumen?
The channel where blood flows
What is the lumen bounded by?
A layer of squamous endothelial cells which rest on a basement membrane
What surrounds the squamous endothelium in the lumen?
A thin layer of loose connective tissue called the intimate
What is the intima bound by?
A layer of elastic tissue called the internal elastic lamina
What is around the lamina in the lumen?
Media
A thick layer of connective tissue generally comprising smooth muscle with some fibroblasts and variable amounts of collagen and elastin
What surrounds the media in the lumen
External elastic lamina
Layer of elastic tissue
What surrounds the external elastic lamina?
Adventitia
Loose connective tissue
What are the elastic arteries?
Large arteries near the heart:
Aorta and Pulmonary arteries
What is the structure of elastic arteries?
Layer of vascular endothelial cells resting on a basement membrane
Loose fibrous connective tissue called intima
Internal elastic Lamina
Media (Abundant concentric sheets of elastin)
External elastic lamina
Adventitia (loose fibrous connective tissue)
What are the most abundant arteries in the body?
Muscular arteries
What is the structure of the muscular arteries?
Lumen
Intima lined on it’s inner surface by vascular endothelial cells resting on a basement membrane
Intima of loose fibrous connective tissue
A muscular media comprising concentric layers of smooth muscle
The media is bounded by an internal and external elastic lamina
Sheets of elastin still found in media
Entire vessel is surrounded by a layer of loose connective tissue, the Adventitia
Give examples of muscular arteries
Radial artery at the wrist
Splenic artery
What are arterioles?
Resistance vessels of the circulation
What is the difference between a muscular artery and arteriole?
Arbitrary
Defined as having 3 or fewer muscle layers in their media
Or artery less than 100 microns in diameter
Can elastic laminae in arterioles be seen?
No elastic laminae are generally poorly defined
What are the differences in structure between capillaries and arteries?
Capillaries don’t have an adventitia, external elastic lamina, media, internal elastic lamina or intima
What is the structure of a capillary?
Layer of vascular endothelial cells resting on the inside of a basement membrane
How is the size of capillaries regulated?
Need to be able to constrict or relax these vascular channels
This is achieved by a layer of cells present on the outside of capillaries called pericytes
What do pericytes do on the smallest capillaries?
Form a discontinuous layer on the outside of the capillary which becomes continuous as the capillaries get larger
What happens when the vascular endothelium is incomplete in some capillaries?
Forms windows that facilitates the movement of materials out of the circulation and into the surrounding tissues, these are the fenestrated capillaries
What are capillaries made of?
Composed entirely of thin-walled endothelial cells with no surrounding muscle or connective tissue
What is meant as ‘closed’ capillaries?
The layer of vascular endothelial cells is complete
What does it mean if the endothelial layer is incomplete?
Creates leaky fenestrated capillaries
Give examples of tissues with fenestrated capillaries?
Kidney and liver
Where do capillaries drain into?
Venous system
What does the venous system begin with?
Venules
What is the difference in structure between arteries and veins?
Veins have no elastic lamina
Arteries and arterioles have a thicker muscular wall and smaller lumen
What are venules typically associated with?
Arterioles
Do venules have thick or thin walls?
Thin walled vessels
What do pericytes do to venules?
Contractile pericytes wrap around outside of endothelial cells and form a complete layer as venules get larger.
What are pericytes replaced with when venules become veins?
Smooth muscle
Muscular smooth muscle media
What happens to the media in larger veins?
The media becomes thicker
Still thinner than in arteries
Describe the structure of smooth muscle in large veins
May be arranged circumferentially around the vein
Longitudinal orientation
Describe the structure of lymphatics?
Thin walled vessels
Have valves
What is the pink material in a histogram or lymphatics?
Lymph
DO NOT CONTAIN BLOOD
What is lymph?
Form of fluid derived from blood plasma
Are blood cells found within lymphatics?
Red blood cells not found
Lymphocytes may be found
What is the main way that lymphocytes travel around the body?
Circulate in the blood
What does the lumen in lymphatics contain?
Amorphous eosinophilic protein rich lymph with scattered lymphocytes
What is the lumen in lymphatics lined with?
Lined with a layer of vascular endothelium
Thin intima and media
Thin Adventitia
What is the structure of peripheral nerves?
Composed of nerves cells which have a cell body typically located in the ganglion and a long axon
What does the axons do in the peripheral nerves?
Form the bulk of the peripheral nerve
Supported by Schwann cells
What do most peripheral nerves comprise of?
Myelinated axons
What does the myelin do?
Acts as an insulating sheath
What is the myelin produced by?
Schwann cells
What is the function of the connective tissue in peripheral nerves?
Binds individual axons together, performs fascicles, and which binds fascicles together to form nerve fibres
What do axons look like on a histogram?
White circles surrounded by thin brown lines
What are the thin brown circles on a histogram?
Myelin sheaths
Why are nerves considered alongside blood vessels?
Commonly found together as a cardiovascular bundle
What stain is used for myelin?
Silver stain
Does not stain readily with H&E
What is the gap between Schwann cells called?
Nodes of Ranvier
What do Schwann cells do?
Envelops and spirals around the axons
Support one or more axons and produce myelin in some cases
What type of axons are larger and transmit impulses faster?
Myelinated Axons
With what type of microscope can neurosecretory granules be seen?
Electron microscope
Where are neurochemicals released from?
Presynaptic bulb
Where do sensory neurons have their cells bodies?
Dorsal root ganglia
Where do sympathetic and parasympathetic neurones have their cell body?
Ganglia and in the brain and local ganglia of all organs
What types of cytoskeleton fibre are contained in neurons?
Microtubules and neurofilaments
What is the myelin mainly composed of?
Phospholipid bilayer with proteins inserted.
Sphinogomyelin is the predominant phospholipid
