1
Q
Describe the organisation of skeletal muscles
A
- Skeletal muscles each have a basement membrane called the external lamina
- Around the external lamina there is a supporting reticular fibre network called the endomysium this carries the smallest capillaries and neuronal processes
- Muscle fibres that work in small groups called fascicles are surrounded by thicker connective tissue layer which is the perimysium
- Fasciles are organised into whole muscles by the epimysium, this is a sheath of dense connective tissue which surrounds it
2
Q
describe the basic organisation of skeletal muscles
A
Inidividual cells are called muscle fibres these are surrounded by the endomysium the perimysium surrounds the fasicle, and the epimysium surrouns the msucles
3
Q
what do the tendons do
A
attach muscle to bone
4
Q
what do the ligaments do
A
attach bone to bone
5
Q
connective tissues in muscles are…
A
continuous with the tendosn and muscle attachments that direct the force of movement to the bone
6
Q
describe the characteristics of muscle cells
A
- Dervied from mesoderm
- Have basement membranes and are supported and organised by connective tissues
- Rely on the interaction of actin and myosin myofilaments for contraction
- Have elasticity in that they can stretch beyond their normal resting length without damage and return to this legnth
- They are able to increase in size (hypertrophy) and number (hyperplasia)
7
Q
How do you stain muscle cells
A
- Stain with H and E due to large amounts of myofilament proteins in their cytoplams
- Cytoplasm takes on a dark pink stianing
- nuclei stained blue
8
Q
What are the three muscle cell types
A
- Skeletal muscle- voluntary
- Cardiac muscle
- Smooth muscle – involuntary
9
Q
Name the properties that all 3 muscle types have
A
- All are contractile
- contain myofilaments
- are composed of actin and mysoin
- they have basement membranes called external laminae
10
Q
what is the sacromere
A
A sarcomere is the functional unit of contraction within the muscle
11
Q
Describe what a picture of skeletal muscle looks like
A
- Nuclei are on the outside and sit underneath the plasma membrane
- Straited
- Many nuclei per cell
- Many cells merge together to become one big cell
12
Q
Describe the structure of skeletal muscles
A
- Muscle fibre = 1 cell with many peripheral nuclei to 10cm in length max
- 1 muscle fibre = 1 cell
- In development individual cells fuse
- Actin and myosin myofilaments are arranged in a regular lattice;
- They have sarcomeres
- Long cylindrical
- Multinucleate
- Straiations
13
Q
What is the function of skeletal muscles
A
- voluntary movement
- Locomotion
- Manipulation of the environmnet
- Facial expression
- Voluntary control
14
Q
where is skeletal muscle located
A
- In skeletal msucles attached to the bones or skin
15
Q
what are the cells present in skeletal muscle
A
- Satellite cells - this is a population of stem cell that can add to the muscle fibre to aid its growth or to form a new muscle cell after damage, found under the muscle fibres and external lamelalle
- fibroblast - help produce the endomysium
- endothelial cells - line the capillaries
16
Q
Name the bands and lines in the sarcomere and what they are
A
- M line where myosin is attached
- Z line where actin is attached and defines the limits of the sacromere
- I base is where actin is only found and therefore it does not overlap with myosin
- A band where myosin is located
- H bands are where only myosin filaments are found
17
Q
What happens to the sarcomere when the muscle contracts
A
- Z lines get closer
- Sacromere shorterns
- Both the I and H bands shortern
- The A band where myosin is remains the same size
18
Q
How does skeletal muscle carry out movement
A
- Attachment of myosin and actin involves shortening which causes the msucle to contract
19
Q
what are myofibrils
A
myofibrils compromise of many sarcomeres which are repeating contractile units of myofilaments and associated proteins
they are formed by cylindrical ropes of sacromeres
20
Q
what are the thick lines in the sarcomere
A
myosin
21
Q
what are the thin lines in the sarcomere
A
actin
22
Q
What is the Z line (how is a sarcomere defined
A
each sarcomere is defined as the distance between sites for actin attachment
23
Q
where is cardiac muscle located
A
it is located in the heart walls only
24
Q
describe the structure of cardiac muscle
A
- Muscle fibre – singel cells called cardaic myocytes that are linked by specail junctions called intercalated disks
- Cardiac myocytes are cylindrical branching cells with a singel central nucleus
- Possess sacromeres and myofibrils
- spaces sometimes have capillaries in them
- Striated
- Branches
- Uninucleate
25
what is the function of cardiac muscle
to constantly properl blood through the body this happens as it contractiosn
- Involuntary contractions
- Automatic ocntractions elicited by physiologic properties of cells, regulated by various factors
26
Describe the cells in the cardiac muscle
- no satellite cells
- Cardiac myocytes cannot divide therefore if it is damaged and the cells die they cannot be replaced and a fibrocollagenous scar is formed in the damaged area instead
27
Where is the smooth muscle located
- in hollow organs
- in viscera (in guts)
- blood vessels
28
Describe the structure of smooth muscle
- Muscle fibre = 1 spindle shaped cell with a single central nucleus
- Actin and myosin myofilaments in bundles criss cross the cell and attach to focal densities at membrane hence ther are no sacroemeres or myfibrils as the cell rounds up with contraction
- Surorunded by connective tissue
- Spidnel shaped
- No straitions
- Cells arrranged closley to form sheets
29
What is the function of smooth muscle
Involuntary control
| - Propels substance sor objects such as urine, food stuff and babies along internal passgaes
30
How is smooth muscle stained
Can be stained by massons trichrome stain that produces a reddish brown stain
31
How does smooth muscle contract
- Contraction mechanism permits fairly continous low force contract with a little amount of energy used
- Regulated by various factors
32
muscles repsond to use by....
by getting bigger
| - this increases the mass and potential of the cell by adding myofilaments, this is hypertrophy
33
what happens if muscle is not used
if they are not used then the muscle becomes smaller this is atrophy
34
what is atrophy
this is when the muscles become smaller as they are not used
35
what is hypertrophy
this is when the muscle becomes bigger due to increased mass and potential of the cell by adding myofilaments
36
describe how each muscle gets larger
1. skeletal muscle
2. smooth muscle
3. cardiac muscle
- Skeeltal muscles – have stem cells called satellite cells which add to muscle firbes to icnrease size this this is hypertrophy
- Smooth muscle cells can hypertrophy and division of cells can occru to increase mass
- Cardiac muscle – hypertrophies but has no stem cells and no cell divison
37
describe muscle regernation in
1. skeletal muscle
2. smooth muscle
3. cardiac muscle
- Skeletal muscle – satellite cells can replace damaged cells if basement membrane is intact
- Smooth muscle can divide and permits regernation
- Cardiac muscle as no stem cells so cannot regernate and has no ability to divide, thereofre fibrocollagenous scare replaces death cells
38
name some other contractile cells
- myoepithelial cells
- myofibroblasts
- pericytes
39
what do myoeptihelial cells do
- Processes which surround secretory portions of mnay exocrine glands
- Contraction of these cells properls secretory product into the duct system
40
What do myofiroblasts do
- Speclaised cells which produce collagen but also have smooth muscle actin and muscle specific intermediate filament desmin
- Function.- wound healing where they proliferate and secrete collagen producing a fibrous scar
- As healing proceeds contraction of myofibroblasts acts to reduce the size of the damaged area
41
what do pericytes do
- Cells with capillaries and small venules where they may have a contractile function
- Following injury the cell proliferate and become stem cells which differnetiate into new endothelila cells, myofibroblasts and fibroblasts
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