Muscles Flashcards
In terms of anatomical identifiers, upper or more medial bony attachments are usually described as…
Proximal/superior
Origin
Lower or more lateral bony attachment is called…
Distal/inferior attachment
Insertion
Which part of a muscle is typically the most stationary?
Origin
How does bone attach to muscle?
Via a muscle tendon
Define muscle tendon. What type of tissue is it? Where do they attach to bone?
The non-fleshy, fibrous, dense regular connective tissue at the ends of a muscle.
At the bone, the fibres of the tendon are embedded in the periosteum. This anchors the tendon and spreads the force of contraction
The anterior tendons of the abdominal oblique muscles are flat, broad and thin. What are these flat tendons called?
Aponeurosis
Skeletal muscle exert their action on ____ which they must ____ to exert their action.
Joints
Cross
Some muscles cross one or more joints and exert their action on ____. Muscles only ___ on bones
Act on both joints
Muscles only pull
What does flexion and extension do to the length of muscle?
Flexion - bend/shorten
Extension - lengthen/extend
How many joints are crossed by the biceps brachii muscle? Name them
Three
Glenohumeral joint
Elbow
Radio-ulnar joint
What is the origin of the long head of the biceps brachii?
Supraglenoid tubercle above the socket of the scapula
What is the origin of the short head of the biceps brachii?
The coracoid process of the scapula
What is the insertion of the biceps brachii?
Radial tuberosity
How is the biceps brachii innervated?
Musculocutaneous nerve (C5-C6)
What 5 functions can the biceps brachii perform? Are they performed by the long or short head?
Abduction (long head)
Internal rotation (long head)
Adduction (short head)
Flexion (both heads)
Supination (both heads)
To which 2 bones are the tendons of biceps brachii attached?
Radius - radial tuberosity
Scapula - supraglenoid tubercle and coracoid process of scapula
What is the action of biceps brachii at each of the joints the muscle crosses - flexion or extension?
Elbow - flexion
Shoulder - flexion
How many joints are crossed by triceps brachii?
2
Elbow
Shoulder
When triceps contracts, i.e., the muscle itself shortens, what action will it have on each of the joints it crosses?
Elbow - extension at the elbow joint
Shoulder - extension at the shoulder joint
What muscle attaches to bone on either side of the midline (i.e. the medial sagittal plane)?
Diaphragm
When the diaphragm contracts, what happens to the muscle?
It descends and flattens
When the diaphragm’s domes contract, do they move superiorly or inferiorly?
Inferior
How does the diaphragm increase thoracic volume?
It’s like bellows. The contraction leads to a low pressure environment and the lungs fill the space
The deltoid has anterior, middle and posterior fibres. What shape of muscle is it and why?
Fan-shaped
Can “pull” on the shoulder joint in different directions
What function do the anterior, posterior and middle fibres of the deltoid do?
Anterior - flexion
Posterior - extension
Middle - abduction
Generally, what 4 functions can the deltoid do?
- Move arm in different directions
- Stabilise shoulder joint, preventing injuries
- Provide support when you carry things
- Side body lifting motions
Where is smooth muscle found?
Organs and BVs
Where is cardiac muscle found?
Heart wall
Define antagonistic pair and give an example
Muscles situated around a joint, or further away from a joint, that can combine in an antagonistic way to carry out a particular action on the joint, e.g. bicep/tricep
When agonists contract, what happens to antagonists? (And vice versa)
They must relax to allow for the joint movement to be performed
Define synergist and give an example
Synergists perform, or help perform, the same set of joint motion as the agonists.
They stabilise muscle movements to keep them even and control their movement so it falls in a safe and desired range of motion
e.g. biceps brachii and brachialis
Define fixator/stabilising muscle and give an example
Primarily stabilise the joint to which they are attached so the joint can move without risk of dislocation, e.g. rotator cuff muscle in the shoulder
What is muscle testing?
A clinical test to help diagnose muscle and nerve injuries by assessing power of movement. Muscles are assessed bilaterally in pairs for comparison
What is muscle atrophy and why might it happen?
“Wasting” of muscle tissue.
May be from disorder of muscle or innervation; or immobilisation, e.g. if in a plaster cast for a long period
Muscles can generally be compartmentalised by what 3 things?
Intermuscular fascial septa
Common nerve/s
Common action/s of muscles
Why is knowledge of the arrangement of the deep fascia and the partitioning of structures into compartments important for clinicians?
To determine the pathway of infection spread from a primary site
In the arm, the fascia separates which 2 muscle compartments?
(general anatomical terminology)
Anterior (flexor) and posterior (extensor)
All arm and forearm muscle compartments are supplied by nerves from a plexus. What’s it called and where is it?
Brachial plexus in the axilla
All thigh and leg muscle compartments are supplied by a nerve network. Where is it and what is it called?
Abdomen and pelvis, called lumbosacral plexus
In which spinal nerve roots does the brachial plexus originate?
Spinal nerve roots C5-T1
Injuries to nerves in C5-T1 nerve plexuses can lead to what 2 clinical things?
Limb muscle paralysis
Distinctive positional deformities of the wrist and hand
The thigh and leg muscles are supplied by nerves originating where, and from which spinal nerve roots?
The posterior abdomen and pelvis, from spinal nerve roots L1-S4
Injuries to nerves arising from the lumbosacral plexus can lead to what 2 clinically relevant things?
Lower limb muscle paralysis
Distinctive positional deformities of the ankle and foot
How many muscles do humans have?
Nearly 700
The oblique muscles have fibres in what direction?
90 degrees to each other
Why are the oblique muscles arranged the way they are?
To make it stronger - more powerful movement and less likely to be damaged
To allow for rotation
What is the shape of the medial oblique muscle tendon and what is the name given to this type of tendon?
It’s narrow and flat
Aponeurosis
Define aponeurosis
Tendon in the form of a sheet
In which direction do the rectus abdominis fibres travel?
Vertically, next to the midline
What does rectus mean?
A straight muscle, e.g. two muscles of anterior abdominal wall
From Latin meaning “upright”
What is aponeurosis made of?
A connective tissue, making it elastic
It’s a flat tendon
What does an aponeurosis attach to?
Attaches a broad/flat muscle to bone
Or
Two broad muscles to each other
The muscles on the anterior abdominal wall (as well as on the anterior chest wall) are broad and flat. How does this affect the movements of the abdominal wall as well as pressure on the organs within the abdomen?
Allows for twisting movements but not lots of power. Keeps pressure in the abdominal wall
What/Where is the serratus?
What can it be divided into?
Fan-shaped muscle along ribs and thorax.
Anterior and posterior
Where is pectoralis, and what can it divide into?
Attach to anterior chest wall
Major and minor
Biceps brachii has how many heads? What about triceps brachii? Quadriceps femoris?
Biceps - 2
Triceps - 3
Quadriceps - 4
Where is the deltoid? What shape is it?
Shoulder
Triangular
Where is teres and what shape does it have?
Below the shoulder joint from scapula to humorous
It is rectangular (though the name means “rounded”)
What shape is the diaphragm? What is it made of and where?
Dome-shaped
Fibromuscular sheet
Extends across midline of the body and partitions cavities
Where does the diaphragm attach?
Centrally to a 3-leafed central tendon and peripherally to various bony structures
Where is the extensor digitorum and what is its function?
Posterior forearm
Extend fingers
What’s the arrangement of a sphincter?
Muscle fibres are arranged circularly and thicekned around the wall of a structure, usually a tube
When the fibres contract they close off the interal diameter
Give 4 examples of sphincters
Between stomach and duodenum
Anal canal and anus
Around urethra
Blood vessels
What type of muscle are most sphincters made of? What are exceptions?
Smooth muscle
Except: Pyloric, e.g. external anal sphincter and external urethral sphincter
To which 2 bones does the sternocleidomastoid attach inferiorly? Which 1 superiorly?
Inferior: Sternum and clavicle
Superior: Temporal bone of skull
What are muscles attaching only to limbs?
Limb/appendicular muscles
How are limb muscles innervated?
Limb nerve plexuses
Brachial plexus for upper limb muscles
Lumbosacral plexus for lower limb muscles
Muscles attaching only to the trunk of the body are called what?
Trunk/axial muscles
How are trunk muscles innervated?
Non-limb nerve plexuses or segmentally, i.e. individual spinal cord nerves that run singly and do not network with each other
Name the two main types of muscle type based on the direction of the fibres
Parallel
Pennate (feather-like)
What’s a muscle called where the fibres are arranged to look like a feather? What if it’s like a feather split vertically?
Bipennate
Unipennate
