Muscles & Nerves Flashcards
How is a longitudinal view of skeletal muscle identified?
- Heavy striations
- Quite straight fibres
- Nuclei pushed to edge of fibres
- fibres seperated by endomysium
How is a cross-section of skeletal muscle recognised?
- Nuclei pushed to the edge of fibres
- Each fibres surrounded by endomysium
- bundled into fascicles surroudned by perimysium
What is different about smooth muscle histology?
images can show cross-sectional areas & longitudinal areas
How is smooth muscle longitudinal section recognised?
Longitudinal:
- Spindle shaped nuclei
- Dense & “blurry”
- no striations
How is smooth muscle cross-sections recognised?
Central nuclei
Not as clearly bundled
Fibres wrapped in endomysium
How is cardiac muscle recognised?
- Branching with gaps
- Intercalated discs (hard af to see)
- light striations
- Largely (but not entirely) mononucleate.
What are axial muscles?
Muscles that attach entirely to the trunk
e.g. rectus abdominis & intercostal muscles
What are appendicular msucles?
Muscles that attach partly or wholly to the limbs
e.g. deltoids, pectoralis & biceps brachii
How do muscles atach to bones?
Via rounded tendons made from dense regular connective tissue
What is the origin of a muscle?
The proximal/superior/medial attachment
What are insertions of a muscle?
The distal/inferior/lateral attachments
Which end of a muscle is moving?
The insertions
What end of the muscle is stationary?
The origin
What is an aponeurosis?
A smooth, flat & broad tendon.
E.g. the tendons of Obliques
What do ligaments do?
Attach bones to adjacent bones across joints to stabilize them
How do muscles connect to joints?
They connect to the bones on either side by tendons on either side
Function/location
Biceps Brachii:
Biceps Brachii connects to the scapula (short & long head) & the radius.
It causes flexion of elbow & shoulder. Also effects supination
Function/Location
Brachioradialis:
Attaches to distal humerus & distal radius.
Causes elbow flexion
Also involved in pronation/supination
Location
Triceps Brachii:
Attaches to the scapula, proximal humerus & proximal radius.
What are diaphragms?
Skeletal muscles that span the mid-sagittal plane (medial plane).
Whats special about a diaphragms tendon?
Its large & centrally located
What does the thoracic diaphragm do?
Seperates the thorax &abdomen.
It increases thoracic volume during breathing. (dome shaped)
What are antagonistic pairs?
2 muscles that combine to carry out a single function
Example of an antagonistic pair
Biceps Brachii & Triceps Brachii
biceps contracts & triceps relaxes to allow elbow flexion
What is a synergist?
Synergists help perform the same motion as an agonist. They stabilize movement & contain it within safe/desired level.
What do fixator muscles do?
They fix a joint in place to allow another joint to move. e.g. roatator cuff muscles lock shoulder joint so biceps can contract to cause elbow flexion
What do stabilizing muslces do?
Stabilize a joint
Often around shouler/hip
e.g. rotator cuff muscles that stabilize the shoulder so it can move without dislocation
How are muscle compartments seperated?
Deep fascial intermuscular septa.
A lateral one between the humerus & lateral side and vice versa on the medial side.
How are muscles in a compartment innervated?
A common nerve innervates all the muscles in a compartment
What nerves supply all arm muscle compartments?
The brachial plexus (C5-T1 vertebrae)
What nerves supply all leg muscle compartments?
The lumbosacral plexus (T12-S4)
How is direction used in muscle naming?
Obliques are named because they arnt parallel or at 90degrees to any plane.
Also rectus means straight musces (rectus abdominis)
How is location used in muscle naming?
E.g. Tibialis Posterior
Tells us the bone (Tibia) & the location (to the back)
Also converse muscles tell us thers usually an opposite.
E.g. seratus anterior tells us theres probably a serratus posterior
What are the 8 areas used for msucel naming?
Location, Attachments, sphincter, action, shape, no of heads, size & direction.
How is size used for muscle naming?
- Major & minor
- Minimus, Medius & maximus
- Longus & Brevis
No. of heads in muscle naming
See triceps (3 heads) & biceps (2 head) In biceps they connect to scapula
Shape in muscle naming
“Teres” refers to rounded muscle.
E.g. Teres Major is a thick & rounded muscle connecting to the proximal humerus & inferior angle of scapula
Action in muscle naming?
Extensor, abductor, pronator etc
e.g. extensor digitorum in posterior forarm extends fingers.
Sphincter in muscle naming?
A sphincter tells us the muscles are arranged circularly & thickened.
Generally involuntary smooth muslce but some voluntary skeletal (e.g. external snal & urinary sphincters)
Attachemnts in muscle naming?
E.g. Sternocleidomastoid muscle
Attaches to sternum, clavicle & mastoid process of temporal bone.
How do somatic nerves exit the spinal cord?
By ventral & dorsal roots.
Ventral - Anterior & motor
Dorsal - Posterior & sensory
What is the mixed spinal nerve?
When the dorsal & ventral roots converge after exiting the spinal cord
Where is the mixed spinal nerve?
In the intervertebral foramen
How do somatic nerves exit the mixed spinal nerve?
As a ventral (anterior) ramus & dorsal (psterior) ramus.
Both contianing sensory & motor nerves.
What does the ventral ramus spply?
The anterolateral sides of the trunk & limbs
What does the dorsal ramus supply?
The posterior side of the body & not the limbs
What kinds of tissue are supplied by rami?
Skeletal muscle
Cartilage
Bones
Skin
What supplies the erector spinae?
The dorsal Ramus
What are the nerves supplying intercostal muscles & how are they numebred?
Intercostal nerves
Numbered by the rib above them
Whats different about the lower half of the intercostal nerves?
The lower 6 (T7-T12) also supply the muscles of the anterior abdominal wall.
What are cutaneous nerves?
Branches of nerves from the brachial and lumbosacral plexus’ supplying the skin.
Whats a dermatome?
An area (strip) of skin supplied by cutaneuous branches of a single spinal nerve
Why is a dermatome smaller than the area supplied by its cutaneuous nerve?
Cutaneuous nerves contain fibres from multiple spinal nerves.
What is the efect of dermatomal overlap?
nerve fibres supplying adjacent dermatomes would have to fail to lose sensation & function in a dermatome
What spinal nerves from the segmental dermatomes of the trunk?
T1-T12 & L1
They relate to the intercostal spaces & msulces
How is longitudinal sections of nerve fibres recognised?
- Wavy
- lighter pink than surrounding tissue
- Many purple nuclei
How are cross-sections of nerve fibres reconised?
- Nuclei of scwann cells at the edge of fibres (PNS)
- endoneurium surrounding every fibres myelin sheaf
- fascicles surrounded by perineurium
What is the main anterior rotator cuff muscle?
The subscapularis muscle
What is the rotator cuff muscle on top?
Supraspinatous Muscle
What is the roatator cuff muscles on the back/
Infraspinatous muscle
Much smaller & inferior teres minor muscles
What joints the humerus to the deep fascia?
The intermuscular septum (radial & medial)
What are the layers betwen the surface & the muscle compratmentS?
Skin, superfical fascia, deep fascia
