Tissue's of the Body Flashcards
0
Q
What is histology?
A
The study of the structure of tissues by means if specific staining techniques combined with light or electron microscopy
- gold standard of diagnosis
1
Q
What is a tissue?
A
A collection of cells specialised to perform a particular function
2
Q
What is a biopsy?
A
The removal of a small piece of tissue from an organ or part of the body for microscopical examination
3
Q
Name the two fixatives commonly used?
A
Glutaraldehyde
Formaldehyde
4
Q
Why do we get shrinkage artefacts?
A
Occurs due to the dehydration and rehydration due the fixing of tissue samples
5
Q
Name the three stains used?
A
- H&E Haemotoxylin and Eosin Blue/purple (acidic) Pink (basic) - Period acid schiff Magenta (stains carbohydrates, glycoproteins and muscous secreting goblet cells)
6
Q
What is the advantage to phase contrast microscopy?
A
- allows us to see the detailed in unstained living cells
- heightened contrast
7
Q
What is the advantage to dark field microscopy?
A
- smaller details are easier to see
- allows detection of syphillus and malaria
8
Q
What is the advantage to fluoresce end microscopy?
A
- can see where individual substance lie within the cells
- can use multiple different fluorescent stains on 1 specimen
9
Q
What is the advantage to confocal light?
A
- can image optical sections via a laser to show 3D structure
- eliminates out of focus flare
- good for imaging living tissues
10
Q
Why do tissues need to be fixed?
A
A fresh biopsy is often wet and bloody so will go off even if we refrigerate it. If fixed the cross linking structure is preserved and there is no auto lysis or putrefaction
11
Q
Define the limit of resolution
A
Minimum distance at which two objects can be distinguished
12
Q
Why are electron microscope capable of finer resolution an light microscopes?
A
Because the limit of resolution is directly proportional to the wavelength used and an electron microscope uses electrons which have a smaller wavelength (depends on voltage used) so therefore has a smaller limit of resolution
13
Q
Define epithelial tissues
A
Sheets of contiguous cells of varied embryonic origin that cover the external surface of the body and line internal surfaces
14
Q
Describe the positioning of the basement membrane
A
Is the thin, felixible, acellualr layer which lies between epithelial cells and the subtending connective tissue
15
Q
What is the structure of the basement membrane?
A
Consists of a basal lamina (laid down by the epithelial cells and leis closets too them) it’s thickness depends on the thick variable, layer of reticular fibres (type II collagen) elaborated by the subtending connective tissue
16
Q
What is the function of the basement membrane?
A
Strong flexible layer to which epithelial cells adhere to
Is a cellular and molecular filter
17
Q
Name and describe the three different types of simple epithelium?
A
Simple squamous
Simple cuboidal
Simple columnar
18
Q
Where might you find simple squamous epithelium and what is its function?
A
Function: lubrication, has exchange, barrier, active transport by pinocytosis
Found: lining of blood & lymph vessels (endothelium), lining of body cavities e.g. Pericardium, pleural sacs, peritoneum (mesothelium), bowmans capsule, loop of Henle, inner and middle ear, respiratory epithelium/pulmonary alveoli
19
Q
What is the function of simple cuboidal epithelium? And where is it found?
A
Function: Absorption and conduit (exocrine glands), Absorption and secretion (kidney tubules), barrier/covering (ovary), hormone synthesis, storage and mobilisation (thyroid)
Found: thyroid follicles, kidney tubules, small ducts of exocrine glands, kidney tubules, surface of ovary
20
Q
What is the function of simple columnar epithelium? And where is it found?
A
Absorption (small intestine, colon, gall bladder)
Secretion (stomach lining, gastric glands, small intestine, colon)
Lubrication (small intestine, colon)
Transport (oviduct)
Can have microvilli
Found: stomach lining, gastric glands, small intestine, colon, gall bladder, large ducts of some exocrine glands, oviducts, uterus, ductuli efferentes of testis
21
Q
Describe Pseudostratified epithelium?
A
Looks multi layered but every cell is attached to the basement membrane
22
Q
What is the function of pseudostratified epithelium and where is it found?
A
Protection, secretion, cilia mediated transport of particles trapped in mucus absorption (epididymis, respiratory tract)
Found: upper respiratory tract (cilia & goblet cells), ductus epididymis, parotid gland, lacrimal sac, large excretory ducts, auditory tube and part of tympanic cavity
23
Q
What does it mean if an epithelium is stratified?
A
It’s is more than one cell thick
24
Name the types of stratified epithelium? (There are 6)
Simple, cuboidal, columnar, stratified squamous keratinised, stratified squamous non keratinised, transitional
25
What is the function of stratified squamous keratinised epithelium and where is it found?
Function: protection against abrasion and physical trauma, prevent water loss, prevents ingress of microbes, shields against UV light damage
Found: surface of skin
26
What is the function of stratified squamous non keratinised epithelium? And where is it found?
Function: protect against abrasion, reduces water loss but remains moist
Found: oral cavity, oesophagus, larynx, vagina, part of anal cavity, surface of cornea, in ER surface of eyelid
27
What is special about translational epithelium?
The surface cells vary in shape from columnar, cuboidal to flattened
28
What is the function of translational epithelium? And where is it found?
Function: can be relaxed or stretched I.e. Distensibility, protection of underlying tissues from toxic chemicals
Found: renal calyces, ureters, bladder, urethra
29
Why are there different rates of renewal for epithelial?
Differ depend in on location & function (& injury)
E.g. Epidermis in skin 28 days, small intestine 4/6 days (powerful hydrolytic enzymes)
Some cease to renew once adulthood is reached but can be triggered to replace cells lost through physical damage or toxic injury
30
What is the function of Junctional complexes?
Bind epithelial cells together so the epithelial cell can act as a gate keeper for what passes through to adjacent cells. Results in preventing of sizeable, molecules passing in between adjacent epithelial cells I.e. Via paracellular route
31
What is metaplasia?
An abnormal change in a type of tissue, change from on epithelial style to another as a result of a stimulus. Often a pre-malignant state.
32
What is neoplasia?
Change resulting from disease e.g. Tumour (neoplasm)
33
Define a gland
An epithelial cell or aggregate if cells that are specialised for secretion
34
What are the four ways of classifying glands?
Destination, structure, nature of secretion and method of secretion
35
What are the two classification of destination in glands?
Endocrine: ductless glands which secretes into the blood stream
Exocrine: gland which deliver the secretions onto a epithelial surface via a duct
36
What are the three classifications by structure of glands?
Secretory part: unicellular/multicellular, acinar/tubule, coiled/branched
Duct system: simple gland (1 duct), compound gland (branched duct)
Branching ducts: main>interlobular>intralobular>intercalated
37
What are the two ways of classifying glands by the nature of their secretion?
Mucous gland: secrete mucous rich in mucins
| Serous gland: have water secretions free id mucous (enzymes)
38
What colour do mucous glands stain in H&E?
Cells stain poorly
39
What colour do serous gland stain in H&E?
Stain pink in H&E
| - eosin stains them pink, basic?
40
What are the three ways of classifying glands by the nature of their secretion? And give an example of each
Merocrine e.g. Parotid gland (acinar serous)
Apocrine e.g. Lactating mammary gland
Holocrine e.g. Sebaceous gland
41
Describe merocrine secretion?
Secretion is Exocytosis
So membrane bound compartment, cell surface membrane is transiently larger, additional membrane removed stabilising cells surface area and only secretory products are released!
42
Describe apocrine secretion?
Non membrane bound structure (lipid), droplet of cell membrane drapes around it, droplet pinches off, plasma membrane transiently smaller so membrane added to regain original cell surface area.
Secretory product + portion of cell surface membrane is released
43
Describe Holocrine secretion
Disintegration of the cell leading to all of its contents being released, I.e. The cell has died
44
Define endocytosis
The process of engulfing material initially outside of the cell
45
What is trans epithelial transport?
The coupling of endocytosis and Exocytosis allowing large molecules that are too large to penetrate membranes to be shunted across one compartment of the body to another.
Describe.....
46
What is glycosylation and where does it occur in the cell?
Is the addition of branching sugars to proteins or lipids
| Occurs in the cisternae of the Golgi apparatus
47
Why does glycosylation occur?
- specificity, offers complex shapes for specific interactions in glycolyax
- adhesion to cells and substrates
- cell mobility
- communication with neighbouring cells
- contact inhibition of movement and division
48
What are the four ways in which secretions from glands are controlled? Giving examples
Nervous e.g. Sympathetic nervous system stimulates release of adrenalin from adrenal medulla
Endocrine e.g. ACTH stimulate released of glucorticoids from adrenal cortex, Zona Fasciculata and Zona reticularis
Neuro-endocrine e.g. Nervous cells in hypothalamus stimulate releases of ACTH from anterior pituitary gland
Negative feedback: e.g. T3 and T4 high levels reduce release and synthesis of TSH from the anterior pituitary gland
Negative feedback
49
What is the role of secretions in cell functions?
In communication: many products of cells that are secretion will go off and bind to a ligand or receptor in another cell in another tissue perhaps stimulating another response/action to occur e.g. Neurotransmitters released into synaptic cleft
50
What are microvilli?
Closely packed finger like extensions of the cell surface membrane, increase surface area for absorption & secretion
51
What are cilia?
Elongated, motile, plasmalemma covered extensions of cytoplasm, move material along cell surface, each one arises from a centriol
52
What are stereocilia?
Are actually long microvilli that branch as well as clump together
Don't move
Precise fixing on is unknown
Found on small cells in ear
53
What are myoepithelial cells?
They are cells that facillitate the movement of secretions along them in a duct
54
What do mucous membranes line? Give examples
Line certain tubes that are open to the exterior
| E.g. Alimentary tract, respiratory tract, urinary tract
55
What are the three layers to mucous membranes?
Epithelium, lamina propria (thin layer of CT), muscularis mucosa (alimentary tract only)
56
What are serous membranes?
Are thin two part membranes which line certain closed body cavities and envelop viscera
E.g. Peritoneum, pericardial sac, pleural sacs
57
What do serious membranes consist of?
Simple squamous epithelium
Connective tissue
Inner membrane = visceral
Outer membrane = parietal
58
Define connective tissue
A huge continuum throughout the body linking together muscle, nerve and epithelial tissue in a structural way and provides support and structure in a metabolic and physiological way.
59
Of what origin is connective tissue?
Mesodermal origin (red-middle)
60
What are the functions of connective tissue?
- provide substance, form, shape to body
- medium for diffusion for nutrients and waste products
- attach muscle to bone (tendons) and bone to bone (ligaments)
- cushion between tissues and organs
- defence against infection
- aid in injury repair
61
What is the function of fibroblasts?
Synthesise and maintain the extra cellular matrix (ground substance and fibres)
62
What are the function of macrophages in CT?
Phagocytosis antigen presenting cells
| E.g. Kuffer cells
63
What is the function of mast cells?
Contain granules in cytoplasm which contain histamine and heparin which when released attracts neutrophils and eosinophils (involved in allergic reactions)
64
What are the cells found in connective tissue?
Fibroblast, macrophages, mast cells,
Plasma cells (secret ab),
pericytes (regulate blood flow through capillaries),
adipose tissue (white - store lipids, brown-heat production, cushion, insulation, shock absorbers)
Leukocyte (production of immunocompleric cells)
65
What is the ground substance?
It is the gel like matrix in which fibres and cells are embedded.
It contains glycosaminoglycans (GAGs) -vecharged so attracts H2O
Proteoglycans
Glycoproteins
ECF diffuses through
Part I'd extra cellular matrix in Ct
66
What are the three types of fibres found in the extra cellular matrix of connect is tissue?
Collagen
Reticular
Elastic
67
How do you classify mesenchymal connective tissue?
Of embryonic origin
Spindle shaped cells with large nuclei
Reticular fibres with small blood vessels
68
How would you classify mucous connective tissue/Wharton's Jelly?
Found in umbilical cord and sub dermal CT of embryo only
Fibroblast with oval nuclei
Collagen bundles and irregular
69
Describe loose/areolar connective tissue?
Cells: many fibroblasts, macrophages, mast cells
EX material: wispy like collagen fibres, elastic fibres, water gs
Examples: adipose, blood, alveolar CT
70
Describe dense regular connective tissue
Cells: elongated flattened fibroblasts in parallel rows
EX material: parallel rows of densely packed collagen (thick)
Examples: tendons, ligaments (high tensile strength)
71
Describe dense irregular connective tissue
Cells: fibroblast and macrophages
EX material: coarse haphazardly arranged bundles of collagen with some elastic and reticular fibres
E.g. Dermis (prevents tearing)
72
Describe reticular connective tissue (special type)
Cells: reticular cells, large oval nuclei, lymphocytes and macrophages
EX material: reticular fibres
Examples: liver, kidney, spleen, lymph nodes, bone marrow
73
What are the macroscopic structures of skin? And what do they vary with?
```
Hair
Thickness
Colour
Wrinkling
Oiliness
Vary with: age, sex, ethnicity, UV exposure, site
```
74
What are the four layers of the epidermis?
Horny layer - stratum corneum
Granular layer - stratum granulosm
Prickle cell layer - stratum spinosm
Basal layer - stratum basalt
75
Describe keratinocyte differentiation
- mitosis mainly occurs in basal layer
- daughter cells move towards prickle cell layer where terminal differentiation begins
- keratinocytes lose their ability to divide
- in granular layer lose plasma membrane and begin to differentiate into corneocytes
- stratum corneum is made up of flattened corneocytes
76
Of what origin are melanocytes?
Neural crest origin
77
Where can melanocytes be found?
Found at interval along basal layer of epidermis
78
What do langerhan cells do in the prickle cell layer of the epidermis?
- mediate immune reactions and present antigens to T lymphocytes
79
Of what origin are langerhans cells?
Bone marrow
| They are dendritic cells
80
What is the layer between the epidermis and the dermis called? Why is it important?
Demo epidermis junction
| - effects prognosis in malignant melanoma
81
What stain is the demo epidermis junction best seen with?
Period acid Schiff
| Stains magneta
82
What then if connective tissue is the dermis? And what fibres should it contain?
Dense irregular
| Contains collagen and elastic fibres
83
What are the skin appendages?
Hair follicles
Sebaceous gland (Holocrine secretion
Sweat glands (merocrine? And apocrine?)
Nails
84
What are the major functions of the skin?
Barrier
Sensation
Thermo regulation
Psychosexual communication
85
What are the disease associated with the skin?
Psoriasis
Vitiligo
Alopecia Areta
Malignancies
86
What surrounds cartilage?
Perichondrium
| Dense irregular connective tissue: fibroblasts, macrophages, bundles of collagen fibres, elastic and reticular fibres
87
What are the cells involved in cartilage?
Chondroblasts, secrete matrix which surrounds and traps cells
Entrapped ones called chondrocytes
88
What are the two types of growth in cartilage?
Appostitional growth: newly formed Chondroblasts round up to develop into chondrocytes
Interstitial growth: isogenous groups result from dividing chrondrocytes deep in cartilage leading to further deposition of matrix
89
What are the three types of cartilage?
Hyaline cartilage
Elastic cartilage
Fibrocartilage - no perichondrium
90
Where can hyaline cartilage be found?
Foetal skeleton, respiratory passageways, joints
| A vascular
91
Where can elastic cartilage be found?
```
- auditory tubes, external ear/pinna, epiglottis
So flexibility (criss cross branching elastic fibres) and support but maintains shape of structures a vascular
```
92
Where can Fibrocartilage be found and why?
Inter ventral disc, meniscus of knees, pubic symphysis, portion of tendons
- support + rigidity
- combination of dense regular CT and hyaline cartilage but no ECM
93
What are the two types of bone?
Compact and spongy bone
94
What connects Haversian canals?
Volkmanns canals
95
What is an osteon?
Each Haversian canal with its surrounding lamellar of bone containing canaliculi radiating to it from the osteocytes trapped in lacunae
96
What connects lacunae?
Canaliculi
97
What is an osteocyte found in?
Lacunae
98
What do oestoblasts do?
Elaborate bone matrix, become surrounded by matrix they synthised and calcify the matrix via matrix vesicles they release
99
What do osteoclasts do?
Are large multinucleated cells derived form monocyte precursors and reabsorb bone
100
What do osteocytes do?
Responsible for the maintenance of bone
Form gap junctions with processes of other osteocytes within canaliculi
Responsible for short term calcium and phosphate homeostasis of body
101
Describe bone remodelling
Haversian canal system is remodelled by a bone remodeling unit:
1. Reabsorption cavity/cutting cone
Done by osteoclasts
2. Lamellar formation/closing zone
Once osteoclasts activity ceases, invasion of capillaries, osteo progenitor cells->osteoblasts and osteoblasts.
Manufacture lamellar of bone until a new Haversian canal system is complete
Process is called coupling!
102
Describe endochondral ossfication
1. Initial hyaline cartilage model
2. Bony sub periosteum collar is formed which then increases in width and length
3. Central cartilage calcify, nutrient artery penetrates bone depositions oestogenic cells given a primary ossification centre
4. Medulla becomes cancellous bone, osteoblasts and cavity filled with bone marrow
5. Cartilage forms epiphysis growth plates and epiphysis develop -> secondary centre of ossification
6. Epiphysis ossify and growth plates continue to move worst lengthening the bone
7. Epiphysis a growth palets eventually replaced by bone but hyaline articulating cartilage persists
103
Describe intramembranous ossification
1. Starts in richly vascularised mesenchymal membranes
2. mesenchymal cells differentiate into oestoblasts which begin to produce/secrete bone matrix forming trabeculae of bone
2. As trabeculae form they fuse forming cancellous bone
3. Cancellous bone in peripheral regions goes to compact bone
Results in newly formed bone called primary/woven bone (arrangement of collagen fibres lacks precise arrangement found in older bone) and via bone remodelling produces secondary/mature bone
104
Where does the mesenchymal membrane that does not participate in intramembranous ossification form?
Soft tissue complement of bone: periosteum and endosteum
105
What is the function and structure of neutrophils?
Function:
Chemotaxis (migrate out of circulation to site of infection)
Phagocytosis of foreign material
Structure:
Multi lobed, small granules in cytoplasm contains digestive enzymes
106
What is the function and structure of basophils?
Function:
Mediate acute inflammatory reactions using heparin (prevents blood clotting) and histamine (vasodilation and oedema)
Structure: bi or tri lobed with large dark purple granules which stain blue (dense dark granules)
107
What is the function and structure of eosinophils?
Function:
Phagocytosis, release cytotoxic enzymes to damage larger particles, allergic reactions, anti-parasite
Structure:
Bi-lobed with small connection between lobes, cytoplasm filled with large granules which stain red (due to Arginine-phospholipid enzymes)
108
What is the function and structure of monocytes?
Function:
Migrates to tissues and differentiates into macrophages, capable of phagocytosis and pinocytosis
Structure:
Kidney shape nucleus, largest circulating blood cell, contain lysosomes
109
What is the function of reticular cells?
Direct t and B cells to specific regions of lympathtic tissue
Synthesise reticular fibres and surround them in the cytoplasm
110
What is the function and structure of lymphocytes?
Function:
Recognise foreign bodies
- B cells Ab forming cells, specific for antigens, interact with T cells
transforming memory cells and plasma cells in lymph nodes
- T cells helper induce profile ration and differentiation of t and B
cells, activate macrophages killer cytotoxic activity inducing
apoptosis
- natural killer cells recognise self and non self killing by lysis, cell
mediated cytotoxicity
Structure:
Small cells with a round nucleus that stains deeply with a ring of pale blue cytoplasm
- if leaves blood returned via lymphatic system
111
What is the function and structure of platelets?
Function:
Adhesion to CT when damaged and aggregate with other platelets on cell surface membranes to facilitate clotting, involved in a traction of blood clotting cascade
Structure:
Small round blue particles, complex cell surface membrane, cytoplasm contains alpha granules produce fibrinogen, dense bodies which contains ADP and Ca2+, rich phospholipid factor lll (extrinsic pathway)
112
What is the structure of red blood cells?
Function:
Delivers oxygen to tissues where required
Structure:
biconcave flexible disc ->8um (facilitates passage through microcirculation), haemoglobin tetramer, 4 haem groups,
113
What is the lifespan of a red blood cell?
120 days
114
How is an erythrocyte broken down?
After 120 days...
1. Breakdown in spleen to Hb to haem
2. To bilirubin which is then conjugated in the liver
3. Bile duct to GI tract --> stercobilin excreted or --> urobilinogen goes to kidney then excreted
Or
4. Bilirubin goes to kidney where it forms urobilinogen which is excreted
115
What is the name of the process by which blood cells are produced?
Haemopoiesis
| Occurs in bone marrow
116
Outline haemopoiesis:
| Proliferation and differentiation
1. Proliferation
A stem cells/haemocytoblast divides forming a replacement and a cells that then differentiates into a blood cell
2. Differentiation
Have a haemoietic progenitor which differentiates into a myeloid blast of a lymphoid blast. This depends on cytokines influence
3. Blood cells are held in the bone marrow by adhesion molecules there is down regulation of receptors for these molecules as the cell matures and eventually it is released into the blood stream.
117
What does a myeloid blast differentiate into?
```
Erythrocyte
Mast cell
Myeoblast -> monocyte ->macrophage
-> basophil, neutrophil, eosinophil
Megakaryocyte -> thrombocytes/platelets
```
118
What does a lymphoid blast differentiate into?
Natural killer cell
Small lymphocyte -> b lymphocyte -> plasma cell
T lymphocyte
119
What are the hormonal abnormalities associated with bone?
Growth hormone:
Before puberty - excessive=gigantism, insufficient=dwarfism
After puberty - excessive=acromegaly (no epiphyseal growth plates so can't cause gigantism)
Sex hormones:
Influences development of ossification centres
Early sexual maturity = retards been growth as premature closing of epiphysis
Deficient = prolonged bone growth + shorts stature, emphysema growth plates persist
120
What is the genetic bases and histological change in osteogenesis imperfecta? And why does it have medical legal importance?
Genetic basis: autosomal dominant, mutation in gene for type 1 collagen so abnormal synthesis by fibroblast
Physiology: bones are brittle, fracture easily, deformity on eyes, ears, teeth, joints-CT
Medical legal: are parents abusing or is it this?
121
Why is vitamin d important in normal bone development?
- essential for normal ossification as it is involved in the absorption of calcium and phosphate by the small intestine via the hormone Calcitrol produced from it
- if absent a poorly mineralised, pliable matrix known as osteoid (the uncalcified matrix secreted by osteoblasts) is formed. Affected bones are unable to support the body weight and bend.
- absence of Vitamin D decreases the calcification of the osteoid (lower calcium absorption) thus prevents Osteoblasts ® Osteoclasts. This is a common cause of Osteomalacia (Rickets in children).
122
Describe the features of bone affected by rickets and osteomalacia?
Rickets: Bone matrix fails to calcify normally, bone matrix called osteoid
- Epiphyseal plate becomes distorted by body weight
- Bones grow slowly and become deformed.
- Bones prone to fractures
Osteomalacia:
- Deficient calcification of recently formed bone decreases calcium levels per bone unit
- Results in the softening of bone
123
What are the differences between rickets and osteomalacia?
Rickets:
Occurs in children, occurs in growing bones
Osteomalacia:
Occurs in adults during bone remodelling
124
What are the dietary and behavioural factors associated with rickets and osteomalacia?
Diet: poor vitamin D intake occurs in immigrants to UK. Need enough vitamin d, calcium and phosphate
Behaviour: children plating computer games inside not outside, people covering skin
- darker skin
125
What are the radiological and histological changes occurring in osteoporosis?
- Bone density is reduced where there is risk of fractures.
- collagen framework and deposited minerals are broken down much faster than they are formed (osteoclast activity > osteoblast activity)
- Medullary canals in the centre of the bone become enlarged and gaps develop in the lamellae, making the bone fragile.
126
What are the common risk factors for osteoporosis?
- genetic (peak bone density if white)
- insufficient calcium, phosphate and vitamin d intake
- insufficient exercise
- cigarette smoking
- being female (reduced secretion of oestrogen in menopause and stimulates osteoblasts less than testosterone)
127
Why is osteoporosis a risk factor for fractures in the elderly?
Less mobile and more prone to falls also more prone to breaks in bones caused by falls which in a young person would not cause a fracture
128
What is the cause of Achondroplasia?
Achondroplasia is a congenital and often hereditary skeletal disorder, caused by failure of proliferation and column formation of epiphyseal cartilage cells
129
Outline the features of Achondroplasia
- defect in endochondral bone formation impairs the longitudinal growth of the tubular bones.
- Skull is unaffected as it is formed by intramembranous ossification.
So:
- Epiphyseal growth plates are thin
- There are few cells in the proliferating zone
- Hypertrophic cartilage cells form irregular columns
- The zone of provisionally calcified cartilage is small and does not provide adequate scaffolding for bone matrix deposition by metaphyseal osteoblasts
130
Skeletal muscle?
| Derived, nuclei, t-tubules, regeneration, structure
Mesodermally derived
Striated
Multi peripheral nuclei
Voluntary
Rapid& forceful
T tubules are triads and are at A-I junction
Can to divide but can regenerate by Mitotic activity of satellite cells
131
Cardiac muscle:
| nuclei, t-tubules, regeneration, structure
```
Elongated centrally positioned nuclei
Intercalated discs
Branching
T- tubules are at diads and are a z-lines
Involuntary
Intrinsic rhythm
Cannot regenerate fibroblast invade and lay down scar tissue
Striated
```
132
Smooth muscle:
| Derived, nuclei, t-tubules, regeneration, structure
Non striated
Single central nuclei (distguished from dense regular CT as part of fibres)
Spindle shaped cells (arrange more in rows)
No sacromers or t-tubules
Slow sub stained rhythm
Filaments arranged diagonally
Have Mitotic activity e.g. Useful in uterus when pregnant
133
What is the structure of the purkinje fibres?
Abundant glycogen
Sparse myofilaments
Extensive gap junctions sites
Large cells derived from monocytes
134
What is the function of purkinje fibres?
Tracts of Purkinje fibres (modified monocytes) transmit action potentials rapidly to the ventricles from the atrioventricular node This rapid conduction enables the ventricles to contract in a synchronous manner.
135
Hypertrophy?
| Muscle size increase, metabolic changes, length of muscle
Replacement > greater than destruction
Muscle size increase:
- increase in no of contractile proteins laid down
- increase in fibre diameter
Metabolic changes:
- increased enzyme activity for glycolysis
- increase no of mitochondria, stored glycogen, blood flow
Adjustment of muscle length:
Frequent stretching results in the addition of sacromeres
136
Atrophy?
Replacement < destruction
Muscle fibres do not die they shrink
Loss of protein therefore reduced fibre diameter therefore loss of power
137
What re the three type of atrophy?
Disuse atrophy: bed rest, limb immobilisation, sedentary behaviour
Muscle atrophy with age: occurs from 30 years (temp reg in elderly)
Denervation atrophy: muscle no longer receives contractile signals required to maintains normal size so replaced with fatty and fibrous tissues -> contractures, disfiguring,
138
What are occurs and what are the conditions associated with neuromuscular junctions?
Myasthenia gravis: autoimmune destruction of the end plate Ach receptors, loss of jucntional folds, widening of synaptic cleft -> crisis when reaches respiratory muscles
- fatigablity, drooping eyelids, sudden falling due to reduced Ach release, double vision
Treatment: acetylcholinesterase inhibitors
Botulism: toxins block Ach release
Organophosphate poisoning:
Irreversibly inhibits acetylcholinesterase so muscle stays contracted e.g. Sarin
139
What is the pathology related to Duchenne muscular Dystrophy?
- complete absence of dystrophin
- since no anchor for actin filaments to sacromeres muscle fibres tear themselves apart
- Creatine kinase released into serum
- calcium enter cell causing necrosis
- get swelling before fat and CT replace muscle fibres
140
What are the signs, symptoms and treatment of Duchenne muscular dystrophy?
S&S:
Gowers sign, contratures (imbalance between antagonistic and antagonistic muscle)
Treatment:
steroid therapy preserves and increases strength of muscle fibres that remain, genetic research
141
What is malignant hyperthermia?
- autosomal dominant
- life threatening reaction to drugs used in general anaesthetics
volatile anaesthetic agents,and the neuromuscular blocking agent succinylcholine.
Succinylcholine inhibits the action of Ach, acting non-competitively on muscle-type nicotinic receptors. It is degraded by butyrylcholinesterase much more slowly than the degradation of Ach by acetylcholinesterase.
Problem: drugs can induce a drastic and uncontrolled increase in skeletal muscle oxidative metabolism, quickly overwhelming the body’s capacity to supply O2, remove CO2 and regulate body metabolism. This eventually leads to circulatory collapse and death if not treated
treatment: correction of hyperthermia, acidosis and organ dysfunction, discontinuation of triggering agents and the administration of dantrolene.
Dantrolene is a muscle relaxant, which works by preventing the release of calcium.
142
What is the type of disease associated with hyaline cartilage?
Osteoarthritis
| Rheumatoid arthritis
143
What type of cartilage is a slipped disc and tearing of a menisci associated with?
Fibrocartilage
144
What are the four main stages in bone repair and fracture?
1. Haematoma formation
2. Fibrocartilganous callsu formation
3. Bony callus formation
4. Bone remodelling
145
What is Paget's disease?
Is the excessive breakdown and from film of bone, so disorganised bone remodelling is seen.
- weakens bone
- typically localised disease
- pain, misshapen bones, fractures, arthritis in nearest joints
Causes are viral and genetic
146
What are the three layers in muscle structure?
Epimysium, Perimysium, Endomysium
147
What is perimysium?
The connective tissue with nerves that is wrapped around each fascicle
148
What is the Endomysium?
Loose connective tissue that ends heaths each muscle fibre/cell
149
What is a sacromere?
The distance between two z-lines
150
What filaments are present at the A band?
Both actin and myosin
151
What filaments are present in the I band?
Actin
152
Where are myosin filament present by themselves?
H zone
153
What does the z line provide for actin filaments?
Attachment
154
Where do myosin filaments attach?
The M-line
155
Watt three filaments make up actin?
Actin
Tropomyosin
Troponin
156
What does tropomyosin do?
Blocks actin binding sites
157
What do the three polypeptides that make up troponin bind to?
TnI - actin bound
TnT - tropomyosin bound
TnC - calcium binds
158
What is a troponin assay used for?
As a marker for cardiac Ischaemia = cardiac damage
159
is myosin a thin or thick filament?
Thick
160
What is the sarcolemma?
the outer membrane of a muscle fibre
161
What is the sarcoplasm?
the cytoplasm of the muscle cell
162
What is the name given to the smooth ER in a muscle cell?
Sarcoplamic reticulum
163
Describe muscle contraction
1. nerve impulse arrives at the neuromuscular junction
2. Voltage gated Ca 2+ channels and Ca 2+ ions influx
3. Release of acetylcholine into the synaptic cleft
4. Binds to receptors on the motor end plate
5. Local depolarisation of sarcolemma caused by sodium channels opening
6. voltage gated sodium channels open so sodium enters the muscle cell
7. Resulting in the depolarisation of the sarcolemma which spreads down the t-tubules which are triads this is at the A-I junction in skeletal muscle.
8. Voltage sensor - proteins of t-tubules change conformation.
9. Casues release of Ca2+ from the terminal cisternae into the sarcoplasma
10. Ca2+ binds to tropmoninC resulting in a conformational change, causing a shift in TnT which is bound to tropomyosin resulting in it moving an the actin binding sites are exposed...... See siding filament model of muscle contraction.
164
Describe the sliding filament model of muscle contraction
1. Myosin heads are bound tightly to actin molecule via cross brdiges.
2. ATP binds to myosin head casuing it to uncouple from actin
3. Hydrolysis of ATP causes the myosin head to bend and advance 5nm
4, Mysoin head binds weakly to actin causing the release of ADP and Pi, this strengthens the binding causing a power stroke pulling the actin filament towards the M-line.
5. The myosin head has now returned to its former position and ATP binds again.
165
What happens to the bands in muscle contraction?
- sarcomere shortens
- H zone disappears
- A band increases
- I band decrease
166
What is botulism?
Toxins block ACh release. e.g. botox cosmetic treatment and certain bacteria found in the soil
167
What is organophosphate poisoning?
irreversibly inhibits actelycholinesterase and muscle stays permanently contracted e.g. nerve gas/sarin
168
What is polymyositis?
Is a type of chronic inflammation of the muscles, it has an auto immune origin. It is related to dermatomyositis
169
What can electrolyte imbalances lead to?
cramps, need diuretic therapy
170
What are the names for the voluntary and involuntary nervous systems?
Somatic and Autonomic Nervous Systems
171
What is a ganglion?
An accumulation of neurone cell bodies
172
What are the differences between the parasympathetic and sympathetic nervous systems?
```
Sympathetic:
Thoraco Lumbar outflow
Short = Pre Long = post
Flight/fright
Parasympathetic:
Cranio Sacral outflow
Long = Pre Short = Post
rest and digest
```
173
What are the receptors present in both parsympathetic ans sympathetic nervous system at the pre ganglion neurone?
Nicotinic ACh receptors
174
What are the receptors present at the sympathetic nervous system at the post ganglionic neurone?
adrenoreceptors, noradrengic
175
What are the receptors present at the post ganglionic neurone in the parasympathetic nervous system?
Muscarinic ACh receptors
176
Describe the structure of peripheral nerves?
Epinerium
Perineurium
Endoneurium
177
What does the epinerium ensheath?
The entire nerve
178
What ensheaths a single cells axon?
The endoneurium
179
What does the perineurium ensheath?
A nerve fasiscle
180
What does saltatory conduction do?
increases the conduction velocity along a nerve
181
In non myelinated cells the axon is.....
surrounded by the schwann cell cytoplasm
182
In myelinated cells the axon has....
schwann cells wrapped around its axon
183
What are the gaps in between the discontinuous myelin sheath called?
Nodes of Ranvier
184
What is the stain used on nerves?
Osium tetroxide
185
What is the disease associated with the formation of sclerosis/scar tissue along neurons. This slows or blocks the transmission of signals to and from the brain and spinal cord so that movement and sensation is impaired.
Multiple Scelorsis
186
What is the role of glial cells in the nervous system?
To support neurones structurally and metabolically,helps maintain homeostasis, forms myelin
187
What do astrocytes do?
Blood brain barrier
assist in the transfer of nutrients and waste
CNS
188
What do oligodendrocytes do?
Myelination (up to 250 cells)
| CNS
189
What cells performs immune and inflammatory functions in the CNS and PNS?
Microgilia
190
What do schwann cells do in the PNS?
Myelination of 1 axon
191
What do Satellite cells do in the PNS?
They provide physical support to peripheral neurones
192
What is special about schwann cells?
They have a high lipid content and do not conduct electricity
193
What are the two horns found in the cross section of the human spinal chord?
Dorsal and Ventral
194
What is found in the centre of a cross section of the human spinal chord?
The central canal containing cerebrospinal fluid.
195
What is in white matter?
Myelinated nerves and their glial cells. Ascending and Descending
196
What is in grey matter?
Neuronal cell bodies and associated fibres
