Histology Flashcards
1
Q
what are tissues
A
aggregates or groups of cells organized to perform specific functions
2
Q
what are the four basic tissues
A
epithelial
connective
muscular
nervous
3
Q
what are the similarites between all tissue types
A
all contain cells
cells that make up tissues have similar functions
4
Q
define epithelium
A
layer(s) of closely apposed cells with a minute amount of intercellular material resting on a basement membrane
5
Q
general functions of covering epithelial tissues
A
cover/line body cavities, organs, surfaces, tubes
6
Q
what the general characteristics and functions of covering epithelial tissues
A
as an interference surface (protection, absorbtion, filteration, secretion, excretion)
exhibits polarity (apical-superior and basal-inferior surfaces)
avascular but innervated
supported by connective tissue
ability to regenerate
cellular
7
Q
two types of classification of covering epithelium
A
on the bases of layers
on the bases of type of cells
8
Q
describe simple squamous epithelium
A
single layer of thin flattened cells
ovoid centrally placed nucleus
9
Q
locations where simple squamous epithelium is present
A
endothelium (internal surfaces of heart, blood vessel, lymphatics)
mesothelium (lines the pericardial, pleural, peritoneal cavities
alveolar epithelium
10
Q
describe simple cuboidal epithelium
A
single layer of cube shaped cells
spherical centrally placed nucleus
hexagonal or polygonal surface view
11
Q
locations where simple cuboidal epithelium is present
A
distal tubules of nephron
surface epithelium of ovary
lining of certain ducts of glands
12
Q
describe simple columnar epithelium
A
single layer of column shaped cells
basally located oval nucleus
13
Q
describe a special property of simple columnar non- ciliated epithelium and its locations
A
may exhibit microvilli to increase SA
lines gall bladder, stomach, intestine
14
Q
describe a special property of simple columnar ciliated epithelium and its locations
A
contains cilia (crew cut appearance)- a dark band extending across the cell at the bas e of cilia due to presence of basal body lines uterine tubes and uterus
15
Q
describe pseudostratified columnar ciliated epithelium
A
single layer of cells resting on basement membrane
not all cells reach luminal surface
nuclei lie at different levels within the basal2/3 of the epithelium
16
Q
location of pseudostratified columnar ciliated epithelium
A
eustachian tubes, nasal cavities, nasopharynx, paranasal sinuses
17
Q
describe properties and functions of stratified squamous epithelium
A
main protective layer
number of layers is variable
polyhedral cells which gradually flatten towards the surface layers
shape o nucleus corresponds to shape of cells
no spaces between cells visible under L/M
they protect underlying tissues
18
Q
special property and location stratified squamous keratinized epithelium
A
non nucleated
contain keratin protein
epidermis of skin
epithelial lining in parts of oral cavity
19
Q
special property and location of stratified squamous non-keratinized epithelium
A
no keratin formation
lines parts of oral cavity, esophagus, oropharynx, lower part of anal canal, vagina
20
Q
describe special property and location of stratified cuboidal epithelium
A
2-3 layers
basal layer low columnar
surface layer cuboidal
ducts of sweat glands
21
Q
describe stratified columnar epithelium and its location
A
non ciliated
parts of ductus deferens and male urethra/ main ducts of salivary glands/ conjunctival epithelium
22
Q
describe the properties of cilia
A
motile extension of cytoplasm covered by cell membrane
contain central pair of microtubules surrounded by central sheath with radial spokes extending from them
nine doublet comprising of A and B subunit surrounding the central sheath
dynein and nexin proteins connect the 9 doublets
A subunit is of 13 tubulin polymers while B subunit is of 10
5-10 micrometer in height 0.2 um in diameter
23
Q
describe microvilli
A
fingerlike projections of cytoplasm covered in cell membrane seen n E/M
striated and brush like border
variable number of microvilli are present on each cell
actin core is anchored at the base by terminal web(myosin 2 and tropomyosin) and at the sides by fascin and fimbrin
apical portion is called apex villin
1-2um in height/ 0.1um in diameter
24
Q
describe stereocilia
A
long microvilli 30um villin is absent erzin replaces myosin 1 alpha actinin is present thick stem is connected by cytoplasmic bridges
25
locations of stereocilia
epididymis of ear
| taste buds
26
locations of microvilli
epithelial cells of small intestine
| epithelial cells of proximal convoluted tubules of nephron
27
locations of cilia
respiratory epithelium
| epithelial lining of uterine tubes and uterus
28
write a short note on flagellum
it is a long motile, whip like projection from a cell
only sperm cells have this
avg length is 55um
produces undulating movements that help in the locomotion of the whole cells
29
describe goblet cell
```
unicellular gland
mucous producing
dilated upper part
stem like base
present in intestinal and respiratory epithelium
```
30
epithelium primarily involved in production of specific substances which are extruded from these cells are called glands
31
glands are classified into
```
exocrine glands (release their products on the epithelial surface)
endocrine ( releae their products into the blood)
```
32
exocrine glands are classified on the basis of
morphology
nature of secretory products
mode of secretion
33
describe the morphology of glands
glands are supported by stroma of connective tissue
connecitve tissue that encloses the gland is called capsule, septa divides the capsule into lobes
thinner lobules further divide it it into lobules
blood nerve and lymphatics run along the connective tissue septa
34
describe myoepithelial cells
epithelial cells having the ability to contract
| secretory protions of some glands are surrounded by these cells
35
simple tubular gland description and examples
secretory portion is a straight tubule
| crypts of lieberkuhns (in small intestine)
36
simple coiled tubular gland and its examples
secretory portion is coiled and long
| sweat glands
37
simple branched tubular glands description and examples
secretory portion is divided into two or more branches with tubular ends
glands of stomach and endometerial glands of uterus
38
simple alveolar glands description and examples
rounded ac like secretory portion
| mucuos glands of penile urethra
39
simple branched alveolar glands description and examples
secretory portion consists of branched saclike secretory parts
sebaceous glands
meibomian glands of eyelids
40
simple tubulo-alveolar glands description and examples
secretory portion consists of branched tubules with sac like alveoli at their distal ends
small salivary glands of oral cavity, mucosal glands of conducting parts of respiratory tract
41
compound branched tubular glands description and examples
secretory portion is branched in long tubules
| submucosal glands of duodenum
42
compound alveolar glands description and example
several saclike units with small ducts converge at larger ducts
exocrine pancreas
43
compound tubulo-alveolar glands
ducts of both tubular and alveolar secretory units converge at larger ducts
salivary glands
44
what is the classification of glands on the basis of mode of secretion
merocrine
apocrine
holocrine
45
describe merocrine secretion and examples of it
most common form of secretion
secretory product is exocytosed without any loss of cytoplasm
salivary gland, lacimal gland and intestinal gland
46
describe apocrine secretion and its examples
apical part of cytoplasm is lost along with its secretion
sweat glands located in axilla and perianal area
ceruminous gland of external auditory canal
47
holocrine secretion description and examples
entire cells laden with secretory molecule disintegrates releasing the secretory products
sebaceous glands
48
describe mucous secretion and its examples
```
pink
flat peripheral nucleus
cellular outline clear
lumen is distinct
no basal basophilia
mucin and glycoproteins released
pyloric gland of stomach
```
49
serous secretion description and example
```
thin watery protein rich secretion
bluish purple appearance
nucleus round and basal
cell outline not clear
lumen indistinct
basal basophilic
```
50
what is connective tissue
diverse group of cells embedded in a tissue specific extracellular matrix
51
what are the components of connective tissue
extracellular matrix
cells
ground substance
52
classification of connective tissue
embryonic CT
| adult CT
53
classification of embryonic CT
mesenchym
| mucous tissue
54
classification of adult CT
CT proper
cartilage
bon
55
describe mesencymal CT
```
primarily in embryo
spindle shaped cells of uniform size with processes
Gap junctions
viscous ground substance
few fine collagen fiber
```
56
describe mucous/mucoid CT
spindle shaped cells widely separated
gelatinous ground substance
wispy collagen fibers
adult pulp of tooth vitreous chamber of eye nucleus pulposus
57
classification of CT proper
loose CT
| dense CT
58
classification of loose CT
areolar
| reticular
59
name the cells of CT
```
fibroblast
macrophages
mast cells
adipose cells
plasma cells
wandering cells
```
60
describe fibroblast according to their forms and their function
inactive: large / somewhat flattened/ cytoplasmic process/ nucleus is small and deeply basophilic. cytoplasm i slightly eosinophilic
active: cell is enlarged/ more cytoplasmic processes/ nucleus is larger/ cytoplasm is slightly basophilic
produce fibers and ground substance for growth and repair
61
describe macrophages and their functions
phagocytic cells derived from monocytes
irregular shape
short cytoplasmic processes
carry out phagocytosis
antigen presenting cells
62
describe mast cells and their functions
large cells with basophilic granules containing histamine and heparin
show metachromasia in toludine dyes
absent in CNS
63
describe fat cells and their functions
large oval cells with signet ring appearance
nucleus is flat and pressed against the cell membrane
specialized to store triglyceride vesicle(s)
in histologic preparation fat is dissolved
white adipose stores fat
brown adipose helps maintain body temperature in newborns
64
describe plasma cells and their functions
B- lymphocytes
large ovoid cells with basophilic cytoplasm due to extensive RER
nucleus is spherical and eccentric and chromatin is coarsely arranged in a regular manner against nuclear membrane giving the cell a cart-wheel or clock face pattern
it produces antibodies
65
what are type of fibers found in CT
collagen
reticular
elastic
66
describe the structure and classification of collagen fibers
made up of collagen proteins (more abundant protein)
formed from tropocollagen (300nm L and 1.5 nm D)
tropocollagen formed of three alpha chains wound together in a helical structure
there are 14 types of collagen (type 1-14)
collagen type 1-3 form fibers while others a non-fibrillar
67
significance of type I collagen
```
most abundant variety of collagen
2-10um in diameter
striations every 64nm
found in dermis/ bones/ fasciae/organ capsule
eosinophilic appearance
```
68
significance of type 2 collagen
found in hyaline and elastic cartilage/ vitreous body of eye
69
significance of type 3 collagen
makes reticular fibers
70
significance of type 4 collagen
found in basement membrane
71
write a short note on elastic fibers
made up of elastin
elastic property is due to random coiling of molecules
yellow color-highly elastic fibers form loose networks
thinner branching
found in ligamentum flavum / lungs and large arteries
72
significance of type 5 collagen
found mainly inn fetal membranes and placenta
73
write a short note on reticular fibers
made of type 3 collagen
stain black with silver dyes
form thin networks in highly cellular organs
found in blood vessels/intestine/uterus/urinary bladder
agryophilic
74
what is ground substance
amorphous, transparent, semi-fluid gel like substance composed of GAGs, proteoglycans, glycoproteins in which cells and fibers are embedded
75
types of GAGs
hyaluronic acid: in loose supporting tissue
| sulphate group attached: chondrotin 4, 6/ dermatan/ heparan/ heparin/ keratan
76
describe GAGs
long unbranched polysaccharide chains of seven different types of repeating disaccharide units
they are acidic due to hydroxyl, carboxyl, sulphate groups attached to them
77
write a short note on proteoglycans
proteins which bind to GAGs
78
write a short note of glycoproteins
proteins attached to polysaccharide
adhesve property
provides strength, ridgidity to ground substance
they form binding sites for cell adhesion molecules and ECM molecules
examples include: fibrillin, fibronectin ,laminin, enactin
79
what is the function of ground substance
```
mechanical and structural support
fills spaces
lubricant
barrier to large molecules
facilitates cell growth and information exchange
```
80
general characteristics and example of loose CT
cellular
viscous gel lke ground substance
thin mesh work of collagen and elastin fiber
highly vascular
superficial fascia beneath epithelium
biological packing material for tissues and organs
bind tissues and organs while allowing a considerable degree of mobility
forms stroma of most organs
81
describe reticular CT and its function
consists of reticular fibers and reticular cells
reticular cells are stellate shaped and have long cytoplasmic processes and are lodged within meshwork of reticular fibers
form the supporting framework of liver spleen, bone marrow and lymphoid organs
some reticular cell posses fibroblastic activity while others give rise to erythrocytes and leukocytes
82
what is adipose tissue
it is composed of adipocytes organized into lobules separated by fibrous septa
83
describe white adipose tissue
```
UnilocularAdipocytes
(Signet Ring)
Spherical Polyhedral shape,
Nucleus Flat
Condensed Lipid + Vimentin
Organic Solvent Xylene
Energy Storage /Insulation & Cushioning Of Vital Organs
Lipomas & Liposarcomas
```
84
describe brown adipose tissue
smaller multilocular
| nucleus round eccentric
85
general characteristics of dense connective tissue
dense packing of fibers
few cell
less ground substance
limited vascular supply
86
dense CT is classified into
regular
| irregular
87
describe dense regular CT
densely packed fibers arranged parallel to each other
flattened elongated fibroblasts present between fibers
occur in the from of tendons, ligaments and aponeurosis
great tensile strength
88
describe dense irregular connective tissue
occurs in the form of sheets
thick bundles of fibers run in all directions
occur in areas subject to mechanical stress
some fibroblasts and macrophages are found between fibers
mostly collagen fibers are present but other fibers are also there
form dermis of skin/ capsules of organs(liver, lymph nodes/ perichondrium/ periosteum
89
state general characteristics of tendon
```
CORD LIKE
WHITE INEXTENSIBLE
CELLS IN ROWS // FIBER
TENDON CELL
ENDOTENDINEUM,EPITENDINEUM
```
90
describe general characteristics of cartilage
Cartilage is a resilient and smooth elastic tissue that can be found in joints and between bones, rib cage, intervertebral discs, ear, nose etc.
It is not as stiff as bone and much more flexible and elastic.
It is avascular
Cartilage is surrounded by fibrous membrane known as perichondrium which is similar to periosteum in structure and function
91
what is perichondrium and describe its layers
Dense layer of fibrous connective tissue covering the cartilage.
Outer fibrous layer. This dense membrane of connective tissue contains fibroblast
cells that produce collagen.
Inner chondrogenic layer. This layer contains fibroblast cells that produce
Chondroblasts and chondrocytes (cartilage cells)
92
which cartilages dont contain perichondrium
hyaline articular cartilage and fibrocartilage
93
describe chondroblasts
produce the matrix of the cartilage, gets trapped in ECM and become less active in producing ECM, therefore become chondrocytes
94
describe chondrocytes
Chondrocytes produce all the structural components of the cartilage such as
collagen, proteoglycans, glycosaminoglycan and helps in repair of matrix
95
what are the types of cartilages
Hyaline Cartilage
Elastic cartilage
Fibrocartilage
96
what are the characteristics of hyaline cartilage
It has thin fibres which are not seen in matrix.
Have bluish glassy appearance because of presence of Chondroitin
Sulphate.
It is quite flexible
Contains type ll collagen
Precursor of bone.
Example: Trachea, nose, larynx, ribs
97
what are the characteristics of elastic cartilage
```
It has numerous yellow elastic fibres.
Colour is yellow and appearance is opaque.
Contains type ll collagen
Maintains the shape of the structure.
Example: epiglottis, external ear
```
98
describe the general characteristics and name examples of fibrocartilage
Type of cartilage with numerous white fibres
Colour is glistening white and appearance is opaque
Only cartilage that contains Type l in addition to Type ll collagen
Example: Symphysis pubis, ligaments
99
what are the general properties of muscle cells
excitability
extensibility
elasticity
contraction
100
muscles are classified on the basis of -------
striated
| non striated
101
striated muscles include
skeletal muscle
cardiac muscle
visceral striatedd
102
describe the characteristics of skeletal muscle cell
```
mesenchymal in origin
variable length (1mm-35cm)
CT supplies nerves and blood vessels
diameter varies (10-100um)
cylindrical shape with rounded ends
multinucleated/ ovoid shape/ peripherally located close to the sarcolemma
cytoplasm filled with myofibrils running parallel to the cell axis
striations seen
```
103
describe characteristics of skeletal muscle
muscle fibers grouped into bundles called fasciculi
muscle fiber is surrounded by endomysium
fasciculi separated form each other by perimysium
whole muscle is surrounded by dense sheath of supporting tissue called epimysium
104
describe the characteristics of myofibril
show alternating light and dark bands
composed of thin (actin 5-7nm diameter and 1.5 um length) and thick filaments (myosin 12-16nm diameter and 1.5um length)
myofibrils arranged parallel to the axis of myofibrils
M line is where mysoin filaments are centrally attached
Z line is where actin is centrally attached
myosin is attached to z line by titin
area between two Z lines is called sarcomere
Central area of sarcomere containing myoin filaments is called A band
while the area bisceted by Z line free of mysoin is called I band
the area where actin and mysoin dont overlap is called H band
105
describe the structure of actin filament
two actin chain round into a double helix
tropomysoin is wound around actin helix and rest in the double helix groves
tropomyosin masks actin binding sites
troponin complex has three subunits I, C, T
106
functions of troponin subunits
I subunit for interaction between actin and troponin
C subunit for binding of calcium
T subunit for binding to tropomyosin
107
describe the structure of mysoin filament
mysoin filaments are made up of myosin proteins
myosin protein has 2 heavy and two light pairs
heavy chain forms the head and the arm of myosin
light chain stablizes the head
108
describe key characteristics of sarcoplasmic reticulum and sarcolemma
t-tubules: sarcolemma form tubular extension of ECF which transverse into muscle fiber
between T-tubules is the sarcoplasmic reticulum which forms a cistern on each side of the T-tubule called terminal cisternae
the T-tubule along with the terminal cisternae is called triad
sarcoplasmic reticulum stares calcium ions
109
describe the blood supply to skeletal muscles
large blood vessels enter epimysium, divide ramify throughout the perimysium, branches from the perimysial arteries transverse along the long axis of muscle fibers (capillary beds from around the muscle fiber)
110
describe nerve supply to the skeletal muscle
innervated by large motor neurons
| a single motor nerve fiber and muscle fibers supplied by it are referred to as motor unit
111
difference between slow and fast muscle fibers
slow/type1/ red muscle fiber:
```
perform aerobic work
slow fibers
abundance of myoglobin
small in cross-section
numerous mitochondria
rich in blood supply
resistant to fatigue
slow contraction
bulky muscle of thigh and leg
```
fast/white/type 2
```
anaerobic work
fast fibers
less myoglobin
large in cross-section
contain less mitochondria
relatively poor blood supply
fatigue rapidly
rapid contraction
triceps' and biceps
```
112
describe cardiac muscles
involuntary but striated
branched syncitium with intercalated discs
collagen tissue supports extremely rich capillary network
113
describe cardiac muscle fibers
striation similar to skeletal muscle
length is about 100um and 15um diameter
single or two nuclei preset centrally
sarcoplasm is more abundant
myofibril form a branched myofibrillar network separated by rows of cytoplasm containing rows of mitochondria and sarcoplasmic reticulum
fat, glycogen and lipofuscin pigment granules seen
114
describe the sarcoplasmic reticulum and T-tubules in cardiac muscle cells
T-tubules lie at the level of Z line
they have greater diameter
terminal cisternae are not formed so triad is not well formed
cisterns narrower with frequent anastomoses
115
describe the structure of intercalated discs
darkly staining areas (o.5-1um) thick
mark the boundary of cell
interdigitate with other cells
always concede with Z line
116
how does the structure of intercalated discs relate to the functioning of cardiac muscle cells
these discs bind the cells
transmit forces of contraction
provide area of low electrical resistance for rapid spread of action potential throughout the myocardium
117
which types of cell junctions are present in intercalated discs
fascia adherens
macula adherens (desmosomes)
gap (nexus) junctions
118
describe fascia adherens
actin filament at the end of terminal sarcomeres insert into fascia adherens and transmit contractile forces from cell to cell
119
describe macula adheren
are less frequent and provide anchorage for intermideate filaments of cytoplasm
120
describe gap junctions
are sites of low electrical resistance through which impulse pass rapidly from cell to cell
121
describe blood supply of cardiac muscles
more extensively supplied than skeletal muscles
| an extremely rich network of capillaries surround the muscle
122
describe nerve supply of cardiac muscle
supplies by sympathetic and parasympathetic nerves of autonomic nervous system
123
describe the differences between skeletal muscles and cardiac muscles
```
SK:
cylindrical shape
well defined striations
intercalated disc absent
less mitochondria
T tubules A I band
terminal cisternae are dilated
Triad present
```
```
CM:
branched syncitium
striations present
single central nucleus
intercalated disc present
mitochondria are more
T tubules are present near Z line
terminal cisternae are absent
Diad present
```
124
describe the structure of smooth muscle
donot show striations
| found in blood vessels and viscera
125
describe smooth muscle cell
spindle shape
diameter 3-8um
length 15-500um
ovoid nucleus located in the central
usually arranged in sheets
densely packed parallel to each other
no myofibrils are present
myofilaments are longtitudinally arranged in cytoplasm and are not as orderly as in skeletal muscle
mechanism of contraction is the same as in skeltal muscle
instead of Z lines there are dense bodies contiaing alpha actin
organelles are mainly concentrated around nucleus
no T tubules but cavelae present in sarcolemma
126
describe nerve supply of smooth muscle cells
multiunitary tye: rich nerve supply- nearly all muscle cells nrecievnerve terminals
example muscles of iris, ductus differens , large arteries unitary : much fewer nerve terminals. adjacent smooth muscle fibers joined together by gap junctions so implses pass from one cell to the next
they are innervated by autonomic nervous system
127
describe blood supply to smooth muscle
not s richly supplied as striated muscle, which is why they appear pinkish white
128
nervous system is classified into
CNS (brain and spinal cord)
| PNS (all other nerves)
129
nervous system is functionally divided into
somatic nervous system (voluntary functions)
| autonomic nervous system (control involuntary functions)
130
describe the characteristics of nervous tissue
nerve cell (structural and functional unit of nervous system) and supporting cells (protect, nourish , maintain neuron)
131
describe the general characteristics of neuron
```
cell body (soma/perikaryon)
processes (axon/dendrites)
```
132
describe the classifications of neurons
morphological
functional
according to length of axon
133
describe morphological classification of neurons
unipolar: only one process (axon) e.g. mesencephalic nucleus of 5 cranial nerve
bipolar: have two process on opposite sides(axon and dendrite) e.g. cochlear neurons , vestibular ganglia, retina and olfactory epithelium
pseudo-unipolar: one process that divides into two branches close to the cell body (axon-CNS/ dendron-periphery) e.g. dorsal root ganglia neurons
multipolar: single axon and multiple dendrites e.g. pyramidal cells of cerebral cortex, purkinji cells of cerebellar cortex, anterior horn cells of spinal cord
134
describe function classification of neurons
sensory neuron: receive sensory stimuli and pass them to CNS
motor neurons: controls the effector such as muscles and glands
interneurons: connect neurons to form complex functional circuits
135
describe the classification of neruon on the basis of length of axons
gogi type 1: long axon that leave the gray matter and passes to other regions of CNS via white matter or leaves the CNS to become a peripheral nerve e.g. Pyramidal cells of cerebral cortex, anterior horns of spinal cord
golgi type 2: short axons which donot leave the part of gray matter in which the cell body of neuron lies . these are numerous in cerebral and cerebellar cortex and most function as interneurons
136
describe cell body of neuron
contains nucleus
nucleus is surrounded by cytoplasm
soma may be 4um in diamter (granule cells of cerebellar cortex) or as large as 135um (anterior horn of spinal cord)
shape varies according to number, orientationn of its processes
globular in pseudo-unipolar
fusiform in bipolar
stellate in multipolar
137
describe nucleus of neuron
```
single
large
pale staining
centrally placed
nucleolus is prominent
```
138
describe cytoplasm of neuron
contains organelles
basophilic nissl granules (RER and ribosomes) present except in axon hillock
microfilaments and neurofilaments are present
139
describe the properties of axon
single process
uniform contour
variable length
cytoplasm of axon is axoplasm
plasma membrane of axon is axolemma
side branches are called collaterals
axon dividing into multiple branches is called telodendria
axon collaterals and terodendria from small knob at their ends called terminal buttons
terminal button form synapses
golgi and nissl substances are absent
contains mitochondria, neurofilaments, microtubules, SER
140
describe the properties of dendrites
afferent process
contain all soma contents except golgi body
present at the sites ofsynaptic contacts
141
describe mylelinated nerve fibers
nerve fibers covered with myelin sheath (composed of lipoprotein myelin)
it is formed by schwann cells in PNS and oligodendrocytes in CNS around he axon
contains nodes of Ranvier
internode is the area between two nodes
142
what is the fnction of myelin sheath
provides insulation to axon
| speeds up the rate of conduction by allowing action potentials to jump from one node to the next (saltatory conduction )
143
describe non myelinated nerve fibers
not convered by myelin sheath
in PNS unmyelinated axons lie in clefts formed by invaginations of schewann cell plasma membrane by the axons
a single schewann cell cell lodges many axons
a ingle unmyelinated nerve axon passes through clefts of a number of schewann cells
in CNS unmyelinated axons are not ensheathed an run fee
144
describe the classifcation of synapses
axodendritic : between axon and dendrite
axosomatic : between axon and soma
axoaxonic : between two axons
dendrodendritic : between two dendrites
145
describe the structure of nerve
nerve fiberes are enclosed within endoneurium
pernurium enclosed fascicles of nerve fibers
endoneurium encircle the whole nerve and contain perineurium
146
describe neuroglia and their types
they are supporting cells of CNS
they are of two types
neuroglia proper and ependyma
147
describe the type of neuroglia proper
astrocytes
protoplasmic astrocytes
fibrous astrocytes
148
describe the properties of astrocytes
```
Largest, most numerous
Long processes expanded pedicles
Protoplsmic & fibrous
Spherical central euchromatic nucleus
Lightly stained cytoplasm
Functions
Supportive
Cover bare areas (nodes of ranvier, synaptic clef
Scar tissue
Movement of metabolite & waste
Maintain chemical environment
Regulation of extracellular environment
Blood brain barrier
```
149
describe protoplasmic astrocytes
grey matter
| short thick processes with many branches
150
describe fibrous astrocytes
white matter
long slender smooth
fewer processes
scarring cells
151
describe oligodendrocytes
both gray and white matter
myelination of CNS
produces myelin for several cells
152
describe microglia
mesenchymal in origin
short banching processes
phagocyticcells
153
describe ependymal cells
simple cuboidal epithelial cells that line the cavities of brain and spinal cord
apical surfaces possess microvilli
they are fluid transporting cell
from junctional complexes
