histology Flashcards
what do astrocytes do?
- maintain appropriate chemical environment for neuronal signalling
- maintain BBB
- provide nutriments
- remove excess neurotransmitters
Where are astrocytes located?
CNS
What do astrocytes look like?
star-like appearance
Where are oligodendrocytes located?
CNS
What do oligodendrocytes do?
-lay down laminated, lipid-rich myelin
What do Schwann cells do?
- lay down laminated, lipid-rich myelin
- participate in regeneration of PNS axons
Where are Schwann cells found?
PNS
What do microglial cells do?
- scavenger cells that remove cellular debris from sites of injury (or normal cell turnover)
- secrete signalling molecules (especially range of cytokines that can modulate local inflammation and influence cell survival or death)
Where are microglial cells found?
CNS
What are the properties of neurones?
- irritability
- conductivity
What are the different types of neurones?
- multipolar
- bipolar
- unipolar
What are the properties of multipolar neurones?
- multiple processes (dendrites/axons)
- motor and sensory neurones
What are the properties of bipolar neurones?
- 2 processes coming off soma
- find them in the eye, inner ear and roof of nose
What are the properties of unipolar neurones?
- one process coming off soma
- sensory ganglia in first order neurone (dorsal root ganglion or ganglion cells for CN)
(What are ependymal cells?) where are they found? what do they do?
- line the ventricles of the brain and central canal of spinal cord
- form cerebrospinal fluid and assist in circulation
What are satellite cells?
equivalent to astrocytes:
- provide metabolic support for neurone
- remove excess neurotransmitter
Where are satellite cells located?
in PNS ganglia
What is a ganglion?
a collection of nerve cell bodies in the PNS
What is a nerve?
bundle of axons travelling in the PNS
What is a nucleus?
a collection of nerve cell bodies in the CNS
What is a tract/fasciculus?
a bundle of axons travelling in the CNS
What is a single neurone called?
nerve fibre
What is the connective tissue layer surrounding a single nerve fibre called?
endoneurium
What is a fascicle?
bundle of nerve fibres
What is a the connective tissue layer surrounding the fascicle called?
perineurium
What is a nerve?
a group of fascicles
What is the connective tissue layer surrounding a nerve?
epineurium
What do both cartilage and bone consist of?
- extracellular matrix
- ground substances (elastic and collagen fibres)
- fibroblasts/cytes
What are the functions of cartilage?
- framework in respiratory tract
- shock absorption and facilitates joint movement
- covers articular surfaces
- development of long bone
What are the properties of cartilage?
firm but flexible, semi rigid
bears mechanical stress without permanent distortion
What does cartilage consist of?
-cartilage cells (CC) (chondrogenic cells and chondrocytes/blasts)
-CC suspended in EMC (extracellular metric)
-cartilage surrounded by perichondrium
(–> cartilage is avascular: receives nutriments from perichondrium)
What are the different cartilage cells?
- -> chondrogenic cells:
- differenziate into chondroblasts
- located into the perichondrium
- -> chondroblasts:
- metabolically active young cells
- manufacture matrix
- located in pericondri but going towards the centre of cartilage)
- become entrapped in lacunae
- mature into chondrocytes
- ->chondrocytes
- mature cells
- maintain matrix
What is the EMC in cartilage composed of?
ground substances and fibres (collagen and elastic):
- proteoglycans: regulate movement of molecules through matrix
- glycosaminoglycans: involved in shock absorption
- glycoproteins: binds fibres, cells and ground substance together
What are the different types of cartilage growth?
- -> appositional growth: (most growth)
- occurs in pericondri
- chondrogenic cells differentiate into chondroblasts
- chondroblasts mitotically divide and lay down matrix
- -> interstitial growth:
- mitotic division of chondrocytes
- increase size of matrix from within
What is perichondrium?
- outer layer: dense irregular connective tissue
- inner layer: chondrogenic calls and chondroblasts
- rich in blood vessels and lymphatics + afferent fibres for pain transmission
What are the different types of cartilage?
Where can they be found in the body?
hyaline cartilage
elastic cartilage
fibrocartilage
What is the characteristic of hyaline cartilage?
Where can it be found in the body?
- only has collagen fibres
- don’t see fibres: glossy, smooth look
-ribs, larynx, trachea
What is the characteristic of elastic cartilage?
Where can it be found in the body?
- elastic and collagen fibres
- looks less glossy then hyaline cartilage (can see some fibres)
-ear, eustachian tube, epiglottis)
What is the characteristic of fibrocartilage?
Where can it be found in the body?
- layers of dense irregular fibres
- doesn’t have perichondrium
- herring bone appearance
- chondrocytes lacunae tend to be fewer and in a row: very resilient to stress
annulus fibrosus, pubis symphasis, TMJ
What are the different parts of matrix around a lacunae called?
territorial matrix
interterritorial matrix
What are the properties of bone?
strong and flexible
What does bone consist of?
–> organic component
-osteoid: glycoprotein ground substance with type 1 collagen fibres
(strong, flexible but easily compressed)
–> inorganic component
-mineral salts mainly calcium hydroxyapatite
(hard, relatively inflexible and quite brittle)
What are the different bone cells? What proportion of bone mass are they?
- osteoblasts: produce new bone, secrete osteoid and responsible for mineral deposition
- osteocytes: mature bone cells, located in lacunae within bone. maintain the matrix
- osteoclasts: remove mineral from matrix, responsible for bone remodelling
- osteogenic stem cells: found in periosteum and endosteum. develop into osteoblasts
How is compact bone structure to resist stress?
-osteons/Haversian system aligned in the same direction: unidirectional strength increase (both not resistant to stress)
-periosteum goes around circumferential lamellae
(concentric, interstitial and circumferential lamellae)
Where do blood vessels enter compact bone?
Volkmann canals
How is cancellous/spongy bone structured to resist stress?
- trabecculae of cancellous bone arranged haphazardly to form network of interconnecting struts: maximum amount of strength for minimum mass
- spaces between trabeculae contain bone marrow
- osteocytes lie in lacunae surface of the trabecullae
- -> trabecullae are orientated along lines of stress
What are fibroblasts compared to chondrocytes/osteocytes?
fibroblasts: non specialised connective tissue
osteocytes/chondrocytes:specialised connective tissue cells
What is a muscle fibre?
cell of muscle tissue
What is a sarcoplasm?
cytoplasm of muscle cells
What is a sarcolemma?
plasma membrane of muscle fibre
muscle unit?
muscle fibre innervated by a single motor neurone
motor unit?
unit of motor activity formed by one motor nerve cell and its many innervated muscle fibres
motor neurone pool?
collection of neurones innervating a single muscle
What are the different muscle types?
skeletal
cardiac
smooth
Skeletal muscle: location morphology control type of work activity cell shape nuclei
connected to bone
striated
voluntary (somatic)
high power
usually relaxed (resting levels of muscle tone)
length of muscle (long and cylindrical in shape)
multiple nuclei, located in peripheries
cardiac muscle: location morphology control type of work activity cell shape nuclei
heart striated involuntary (autonomic) high power pump (cyclic) branch fibres, connected by interconnected disc, short 1-5 centrally located nuclei
smooth muscle: location morphology control type of work activity cell shape nuclei
hollow organs
smooth
involuntary (autonomic)
low power (slow contraction: basal muscle tone)
usually contracted (varies)
short, fusiform (wider in middle, spindle form)
central (1/cell)
What are
endomysium
perimysium
epimysium?
connective tissue around:
endomysium: single muscle fibre
perimysium: fascicle (bundle of muscle fibres) (often have blood feels running through it)
epimysium: muscle
Wha are the different types of fast twitch fibres? What respiration is used?
- type IIa: intermediate fast twitch, use both aerobic and anaerobic respiration
- type IIb: use only anaerobic respiration
What is succinate dehydrogenase? Where do you find it? Which type of muscle fibres?
enzyme in Krebs cycle (electron transport chain)
mitochondrial membrane
–> found in slow twitch muscles
What are muscle spindles?
What do they consist of?
-sensory receptors that detect muscle stretch (length)
- spindle cells: nuclear bag fibres and nuclear chain fibres surrounded by an internal capsule
- internal capsule: within fluid filled space surrounded by external capsule
- sensory nerve endings wrapped around spindle cells detect stretch
Why is there a reflex response?
muscle shortening to not overstretch
type 1 fibres (oxidative slow, red):
- myosin
- Ca pump transport rate
- diameter
- oxidative capacity
- glycolytic capacity
- fatigue
- slow
- moderate
- moderate
- high
- moderate
- resistant (++ mitochondria and myoglobin)
type 2B (glycolytic fast, white)
- myosin
- Ca pump transport rate
- diameter
- oxidative capacity
- glycolytic capacity
- fatigue
- fastest
- high
- large
- low
- high
- non resistant (no mitochondria)
type 2A (glycolytic fast, red)
- myosin
- Ca pump transport rate
- diameter
- oxidative capacity
- glycolytic capacity
- fatigue
- fast
- high
- small
- very high
- high
- resistant (few mitochondria)
