Changes

Jump to navigation Jump to search
no edit summary
Line 1: Line 1:  +
<big><center>[[Musculoskeletal System - Anatomy & Physiology|'''BACK TO MUSCULOSKELETAL ANATOMY AND PHYSIOLOGY''']]</center></big>
 +
 +
 +
===Introduction===
 +
 +
*Skeletal muscle includes muscles of:
 +
**Posture
 +
**Movement
 +
**Respiration
 +
 +
 +
*Two basic types of skeletal myofibre:
 +
**<u>'''Type I'''</u>
 +
***Grossly '''red'''
 +
***'''High''' myoglobin level
 +
***'''Slow''' rate of contraction
 +
***High '''oxidative''' activity
 +
***Function - postural
 +
**<u>'''Type II'''</u>
 +
***Grossly '''white'''
 +
***'''Low''' myoglobin level
 +
***'''Fast''' rate of contraction
 +
***High '''glycolytic''' activity
 +
***Function - exercise
 +
 +
 +
*Each muscle is composed of multiple '''fascicles'''
 +
**Each fascicle is composed of multiple polygonal '''myofibres'''
 +
 +
 +
===Response to injury===
 +
 +
*Limited array of ways in which to respond to injury
 +
**[[Muscles - degenerative#Degeneration|Degeneration]]
 +
**[[Muscles - degenerative#Necrosis|Necrosis]]
 +
**[[Muscles - normal#Regeneration|Regeneration]]
 +
**[[Muscles - degenerative#Atrophy|Atrophy]]
 +
**[[Muscles - hyperplastic and neoplastic#Hypertrophy|Hypertrophy]]
 +
 +
*Large number of factors indicing the changes above, e.g.:
 +
**Trauma
 +
**Toxins
 +
**Infectious agents
 +
**Nutritional deficiencies
 +
**Ichaemia
 +
**[[Muscles - developmental|Hereditary diseases]]
 +
 +
 +
 +
*Specific diagnosis is often not possible based on morphological or histological features alone
 +
*Additional tests, clinical information and history are often required
 +
 +
 +
 +
===Regeneration===
 +
[[Image:Muscle regeneration.jpg|right|thumb|100px|<small><center>Muscle regeneration (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 +
 +
*Skeletal muscle myofibres have substantial regenerative ability
 +
*Success depends on:
 +
**An intact '''sarcolemmal tube''' - to act as a support and guide
 +
**Availability of '''satellite cells''' - to act as progenitor cells for new sarcoplasm production
 +
**Macrophages to clear up cell debris
 +
**If these conditions are not met (e.g. severe thermal damage) '''fibrosis''' will occur
 +
*Stages:
 +
#Nuclei in [[Muscles - degenerative#Necrosis|necrotic segement]] disappear, hyalinased sarcoplasm due to loss of normal myofibrillar structure, may separate from adjacent normal myofibrils and/or [[Muscles - degenerative#Calcification|mineralise]]
 +
#Monocytes from capillaries -> macrophages in necrotic portion, satellite cells swell -> vesicular with prominent nucleoli -> mitosis (within 1-4 days after initial injury)
 +
#Satellite cells move to centre
 +
#Macrophages clear the sacrolemmal tube, plasmalemma disappears, shape maintained by basal lamina
 +
#Satellite cells -> myoblasts (contain myosin) -> fuse forming myotubes with row of central nuclei; cytoplasmic processes fusing
 +
#Growing and differentiating fibre, striations appear - formation of sarcomeres
 +
#Nuclei move to peripheral position (2-3 weeks after initial injury)
 +
*Regeneration by '''budding'''
 +
**When conditions are not optimal, disrupted sacrolemma
 +
**E.g. injection of irritating substance, trauma, [[Muscles - degenerative#Ischaemia|infarction]]
 +
**Myoblasts proliferate -> sacrolamma bulges from cut part -> club-shaped with numerous central nuclei = muscle giant cells
 +
*Monophasic lesions - all at same phase above
 +
**Damage occured at one time, e.g. trauma or one toxin exposure
 +
*Multiphasic lesions - different stages as described above
 +
**Ongoing damage, e.g. vitamin E - selenium deficiency, continuous exposure to toxin
 +
 +
 +
===Rigor Mortis===
 +
 +
*Muscles remain biochemically active after the death of an animal
 +
*Following a period of relaxation, contraction and stiffening occurs
 +
*Due to deficiency of ATP releasing myosin heads from their binding sites at end of power stroke
 +
*Onset faster in ATP deprived animals (starvation, hunting, tetanus...)
 +
*May be absent in cachetic animals
 +
*Disappears due to autolysis or putrefaction
 +
*See [[General Pathology - Post-Mortem Change#Rigor Mortis|general pathology]]
 +
 +
 +
 
<big><center>[[Musculoskeletal System - Anatomy & Physiology|'''BACK TO MUSCULOSKELETAL ANATOMY AND PHYSIOLOGY''']]</center></big>
 
<big><center>[[Musculoskeletal System - Anatomy & Physiology|'''BACK TO MUSCULOSKELETAL ANATOMY AND PHYSIOLOGY''']]</center></big>
1,351

edits

Navigation menu