Blood Vessels And Nerves

Question 1

General structure

Answer 1

1. Endothelium on a basement membrane
2. Intima
3. Internal elastic lamina
4. Media
5. External elastic lamina
6. Adventitia

Question 2

Loose connective tissue layers

Answer 2

Intima and adventitia

Question 3

Thick connective tissue layer

Answer 3

Media- comprising smooth muscle with some fibroblasts and varying amounts of collagen and elastin

Question 4

Elastic arteries

Answer 4

arteries near the heart eg. Aorta, pulmonary arteries
• media contains abundant concentric sheets of elastin
• Elastic recoil helps to smooth pressure surges from the heart and drives blood around the coronary circulation during diastole
• Have a blood supply of their own (vasa vasorum)

Question 5

Muscular arteries

Answer 5

most arteries are muscular arteries
• media comprises of layers of smooth muscle and little elastin
• eg radial artery, splenic artery

Question 6

Arterioles

Answer 6

resistance vessels
• arbitrarily defined as having 3 or fever muscle layers in the media
• up to 100um diameter
• elastic laminae poorly defined

Can be closed due completely due to contraction of smooth muscle

Question 7

Criteria for an arteriole

Answer 7

3 or fewer muscle layers in the media
• up to 100um diameter

Question 8

Capillaries

Answer 8

no adventitia, external elastic lamina, media, internal elastic lamina, intima
• only a layer of vascular endothelial cells resting on a basement membrane
• pericyte- layer of cells present on outside of capillary. Becomes continuous as capillary becomes larger. Cells that constrict or relax to regulate size of capillaries
• fenestrated capillaries- endothelial layer is incomplete forming pores that facilitate movement of materials into surrounding tissues eg kidney, liver
• Closed capillary substances are transported across membrane by diffusion or pinocytosis

Question 9

What are fenestrated capillaries

Answer 9

endothelial layer is incomplete forming pores that facilitate movement of materials into surrounding tissues eg kidney, liver

Question 10

Sinusoids

Answer 10

large diameter, thin walled vessels with a fenestrated endothelium. They have poorly developed basement membrane but are supported by surrounding tissues eg liver and spleen

Question 11

Does all blood pass through capillaries

Answer 11

Not all blood passes through capillaries. Lots of arterio-venous shunts that allow some blood to pass directly from arteriole to venule. Most organs can control their perfusion

Question 12

Venules

Answer 12

associated with arterioles
• Have valves
• Thin walled
No external elastic lamina
• Contractile pericytes wrap around outside of endothelial cells and form a complete layer as venules get larger
• pericytes replaced by smooth muscles as venues become veins

Question 13

Veins

Answer 13

• no external elastic lamina
• thinner muscular wall (media) and larger lumen
• Have valves
• Smooth muscles in wall may be circular or longitudinal

Question 14

Lymphatics

Answer 14

thin walled (similar to capillaries and veins)
• have valves
• do not contain blood - contain eosinophilic lymph and may contain lymphocytes (stains pink)
• wall of the lymph capillary is composed of endothelium in which the simple squamous cells overlap to form a simple one-way valve

Question 15

Peripheral nerves

Answer 15

composed of neurons: consist of a cell body (often found in a ganglion) and long axons

Unipolar - 1 process
Pseudo-unipolar - apparently 1 process
Bipolar - 2 processes
Multipolar - more than 2 processes

Question 16

Endoneurium

Answer 16

Present between individual axons

Question 17

Perineurium

Answer 17

surrounds the groups of axons to form fascicles

Question 18

Epineurium

Answer 18

binds fascicles together to form nerve fibres

Question 19

Where are cell bodies of motor neurons

Answer 19

Grey matter of spinal cord

Question 20

Where are cell bodies of sensory neurones

Answer 20

Dorsal root ganglion

Question 21

Where are cell bodies of sympathetic neurons

Answer 21

Grey matter of spinal cord and adjacent sympathetic ganglia

Question 22

Where are cell bodies of parasympathetic neurons

Answer 22

Brain and local ganglia

Question 23

Nerve cell fibrous proteins

Answer 23

Microtubules- assemblies of tubulin and dynein. Transport vesicles from Golgi body in neuron cell body to end and back of axon. involved in forward (anterograde) and backward (retrograde) movement of organelles and substances along axons
Neurofilaments- determination of axon diameter

Question 24

Nissl substance

Answer 24

rER. Well-developed in neurons as have a large surface area (cell membrane) and large number of vesicles whose neurosecretions are discharged from the cells

Question 25

Mesoaxon

Answer 25

point where the 2 limbs of the Schwann cell or oligodendrocyte that engulf the axon fuse. It is the focal point where myelin is inserted into the myelin sheath

Question 26

Satellite cells

Answer 26

surround nerve cell bodies and play a supportive role, plying the nerves with nutrients, growth factors etc

Question 27

Neurosectretory granules

Answer 27

found at neuro-chemical synapse:
• two most common types: cholinergic (release acetylcholine) and adrenergic (nor-adrenaline)

Question 28

Myelin

Answer 28

• insulates axons
• a spiral of apposed Schwann cell membranes
• one axon per Schwann Cell, multiple Schwann cells per myelinated axon
• gaps between Schwann cells = Nodes of Ranvier- depolarisation occurs at these points and action potential passes from one node to the next in a saltatory fashion
• Myelinated axons are larger and transmit faster impulses than unmyelinated ones- faster conduction velocity 10-100ms compared to 1-20m/s
• Most of myelin is extracted by conventional tissue processing leaving clear spaces or causing collapse within the nerves

Question 29

Myelin structure

Answer 29

Myelin is membranous in nature and consists of a bilipid layer with proteins inserted into it and spanning the layers. Sphingomyelin is the predominant phospholipid. Number of proteins and lipoproteins including proteolipid proteins, myelin basic protein, PO protein and peripheral myelin protein

Question 30

Schwann cells

Answer 30

supported by continuous chain of Schwann cells (200um long)- myelinated (one Schwann cell per axon) and unmyelinated (multiple axons per Schwann cell)

Question 31

Neuromelanin

Answer 31

found in large quantities in neurons if substantia nigra (region of brain containing dopamine)

Question 32

Lipofuscin granules

Answer 32

breakdown products that are not fully digested and accumulate within the perikaryon of sympathetic ganglia cells

Question 33

CNS

Answer 33

brain and spinal cord and contains most of the cell bodies. Supporting cells = oligodendrocytes

Question 34

PNS

Answer 34

consist of mainly axons processes passing to target organs and tissues. Supporting cells = Schwann cells

Question 35

Axon hillock

Answer 35

contains vesicles drives from the Golgi body, site of origin of nerve stimulus. Seen as a pale zone in the perikaryon (cytoplasm surrounding nucleus) at entry to axon

Question 36

Can a severed nerve regenerate

Answer 36

If the cell body survives, a nerve fibre can regenerate but never quite as good. Can grow at 1-2cm per week

Question 37

What is the predominant myelin membrane phospholipid

Answer 37

Sphingomyelin

Question 38

Cell bodies: motor neurons

Answer 38

Grey matter of spinal cord

Question 39

Cell bodies: sensory neurons

Answer 39

Dorsal root ganglion

Question 40

Cell bodies: sympathetic neurons

Answer 40

Grey matter of spinal cord and adjacent sympathetic ganglia

Question 41

Cell bodies: parasympathetic neurons

Answer 41

Brain and local ganglia