Muscular System

Question 1

What are the three types of muscle?

Answer 1

Voluntary/skeletal/striated
Involuntary/Smooth/unstriated
Cardiac

Question 2

Describe skeletal muscle

Answer 2

Under conscious control
Attached to skeleton
Made up from peripherally nucleated cells
Typically long muscles that lie parallel to each other
Tires quickly
Good blood supply

Question 3

Describe the structure of skeletal muscles

Answer 3

Each muscle cell is made up of a bunch of thread-like fibres called myofibrils. Each fibril is enveloped in a sheath of connective tissue called sarcolemma.
A ‘bunch’ of these fibrils are then bound together by a connective tissue called endomysium and then enclosed in another sheath called Perimysium.

On a larger scale. A few of these structures are then surrounded by Epimysium.

Question 4

What can a tendon also be known as?

Answer 4

Aponeurosis

• a broad, sheet-like tendon
• e.g. linea alba of abdomen

Question 5

What is the difference between fleshy and tendinous muscle?

Answer 5

Fleshy muscle has little fibrous attachment, whereas tendinous muscle is more fibrous

Question 6

Describe the parts of a muscle

Answer 6

Origin
- point of attachment which moves least when the muscle contracts i.e. where the muscle starts essentially

Insertion
-the point of attachment which moves the most i.e. where it attaches to the bone

Belly
-fat part of the muscle

Head
-Tapered part of the muscle. Can be at both ends. Usually at the origin.

Question 7

Name and describe an antagonistic pairing

Answer 7

Opposing Actions
e.g. flexion and extension of the forelimb

Flexion: Biceps contract (agonist), Triceps relax (antagonist)
Extension: Biceps relax (antagonist); triceps contract (agonist)

Question 8

Describe involuntary muscle

Answer 8

Not under conscious control
Controlled by autonomic nervous system
Do not tire easily
Made up of spindle shaped cells with a nucleus
No muscle sheath
Bound together by connective tissue
e.g. walls of bladder, bowel, blood vessels etc

Question 9

Describe Cardiac muscle

Answer 9

ONLY found in heart
irregularly striped
Involuntary
made up of short, cylindrical branched fibres that have a centrally located nucleus

Question 10

Name the 6 functions of the muscles

Answer 10

1. Cause movements of bones at a joint
2. Move complete limbs
3. Supportive structures of abdominal walls
4. Opening and closing of sphincter
5. Opening and closing of eyes
6. Rigidity of limb muscles if necessary
   (fight or flight)

Question 11

Name and describe the 2 fibrils that make up muscles

Answer 11

Myosin - thick fibrils with side arms

Actin - thin fibrils

Question 12

How does muscle contraction work

Answer 12

Breakdown and re-attachment of actin and myosin fibrils

Question 13

What controls muscle contraction

Answer 13

Motor Neuron Nerves via the CNS.

The nerve enters the muscle belly and diverges. All muscle fibres activated by one nerve fibre is called a motor unit

Question 14

What is muscle tone?

Answer 14

Normal muscles exist in a state of slight tension called muscle tone - keeps animal upright.
It occurs by a few nerve impulses reaching the muscle from the CNS

Question 15

Describe Hypertrophy and Atrophy

Answer 15

Hypertrophy - when frequently used muscles increase in strength and bulk.
Atrophy - when unused or damaged muscles become wastage

Question 16

Name and describe the two types of muscle contraction

Answer 16

1. Isometric
   - increase in muscle tone, but no change in length
   - e.g. pushing against a wall
2. Isotonic
   - no change in tension, but muscle shortens
   - e.g. repetitive lifting of limb

Question 17

What does muscle activity require, generate and monitored by?

Answer 17

Requires energy and calcium ions for chemical reaction
It generates heat
Its monitored by stretch receptors in muscles, tendons and joint capsules

Question 18

Define intrinsic muscles

Answer 18

Originate in the head region
Change position of part of the head
Do not change the position of the head relative to the rest of the body.

Question 19

Define extrinsic muscles

Answer 19

Originate externally
More superficial
Change position of head relative to body

Question 20

Name and describe the 3 intrinsic muscles of chewing

Answer 20

1. Temporal Muscles (close jaw)
2. Masseter muscles (close jaw, chewing action)
3. Digastricus muscle (open the jaw)

Question 21

Describe the muscles of facial expression

Answer 21

Intrinsic
Found on face and around mouth, ears, eyes, lips and nose.
Innervated by Cranial Nerve VII (7)
Move face without moving the head e.g. smiling, winking

Question 22

Name and describe the extrinsic muscles of the eye

Answer 22

Control eye movement
Found in the orbit of the skull

1. Rectus muscles
   - 4 of them: Dorsal, ventral, lateral, medial
   - Insert on the sclera at the equator of the eye
   - each muscle moves the eye in its direction e.g. Up, down, out and in
2. Dorsal and Ventral oblique
   - Come in at opposing angles
   - rotate eye around visual axis
3. Retractor Bulbi
   - Forms muscular cone around optic nerve
   - keeps eye in socket

Question 23

What muscles are responsible for head movement and where do they attach?

Answer 23

Extrinsic muscles attach occipital bone of the skull to the atlas of the vertebral column

Question 24

Describe the muscles of the vertebral column

Answer 24

Hypaxial muscle - found on ventral surface of transverse process. Function to flex the head, neck, tail and vertebral column

Epaxial muscle - found on dorsal surface of the vertebral column. Action to support the spine and extend the vertebral column

Question 25

What are the muscles of the thorax?

Answer 25

1. External intercostal muscles - responsible for inspiration 2. Internal intercostal muscles - responsible for expiration 3. Diaphragm - sheet of muscle tendon that contracts to increase volume of thoracic cavity and draw air into lungs

Question 26

Where does the diaphragm attach to the vertebral column and what is present here?

Answer 26

Attaches to the ventral surface of the lumbar vertebrae. At this point there is a pair of thickened muscle fibres called crura - they spread towards the head and across the dorsal surface of the ribs.

Question 27

In what direction is the diaphragm domed?

Answer 27

Cranially

Question 28

What are the 3 openings of the diaphragm and what passes through them?

Answer 28

1. Aortic hiatus - allows transmission of aorta, azygous vein and thoracic duct 2. Oesophageal hiatus - allows transmission of oesophagus and vagus nerve 3. Caval foramen - Transmits the caudal vena cava

Question 29

What is the inguinal canal?

Answer 29

A slit between the abdominal muscles. If enlarges can cause inguinal hernia and abdominal contents can slip under skin

Question 30

Name the 4 muscles of the abdominal wall

Answer 30

1. External abdominal oblique 2. Internal abdominal oblique 3. Transverse abdominus (deepest) 4. Rectus abdominus

Question 31

Describe the layout of the abdominal muscles

Answer 31

The external, internal and transverse abdominal oblique muscles all run in different directions to form a mesh work. They all meet at the Linea alba (runs mid-ventrally along abdomen extending from the sternum to the pelvis). The rectus abdominus runs parallel to the linea alba, but does not attach directly onto it. It inserts onto the pubis via the prepubic tendon - it supports the ventral floor of the abdomen.

Question 32

Describe what the function of intrinsic and extrinsic muscles of the limbs are

Answer 32

Intrinsic - move parts of the limb in relation to other parts of the limb - Runs between bones of appendicular skeleton e. g. flexion and extension of limbs Extrinsic - Moves limb as a whole relative to the body - Run between trunk and limbs - e.g. protraction (abductor and adductor muscles) and retraction of limbs

Question 33

Where do protractor and retractor muscles attach?

Answer 33

Protractor muscles attach to trunk cranial to limb and to limb ventral to the joint. Retractor the opposite

Question 34

Describe the muscles of the skin

Answer 34

- called cutaneous muscles - causes 'twitching' - very thin muscles - Only attached to skeleton in a few places

Question 35

What type of tissue is a tendon?

Answer 35

Dense regular connective tissue | Attaches muscle to Bone

Question 36

Describe the achilles tendon

Answer 36

Runs down back of leg to hock Includes the tendons of insertion of the gastrocnemius muscle, the biceps femoris, semitendinosus and the digital flexors

Question 37

What is a bursa and give an example of where you would find one?

Answer 37

Small sac of fibrous tissue lines with synovial membrane containing synovial fluid. Located between ends of bones or where tendons or ligaments pass over bony prominences e.g. point of hock

Question 38

What are bursal elongations?

Answer 38

Extensions of the cavity which form pouches to lie between tendons and extremities of bone

Question 39

What is it called if a bursa completely surrounds a tendon?

Answer 39

Synovial sheath

Question 40

What is it called if a bursa has formed in an unusual place?

Answer 40

Adential or acquired bursa

Question 41

Name the 4 extrinsic muscles of the forelimb

Answer 41

1. Trapezius - draws leg forward and protracts the limb 2. Latissimus dorsi - retracts the forelimb and pulls leg backwards 3. Pectorals - adduct the limb and hold the forelimb against the body wall 4. Brachiocephalicus - - Protracts the limb and bends neck laterally from side to side

Question 42

Name and describe the action of the intrinsic muscles of the shoulder

Answer 42

1. Supraspinatus - Extends the shoulder and stabilises the shoulder joint 2. Infraspinatus - flexes the shoulder joint and stabilises the joint

Question 43

Name and describe the action of the intrinsic muscles of the Elbow

Answer 43

1. Triceps Brachii - extends the elbow joint 2. Biceps Brachii - flexes the elbow joint, extends the shoulder 3. Brachialis - flexes the elbow joint

Question 44

Name and describe the action of the intrinsic muscles of the Carpus

Answer 44

1. Carpal extensors - extends the carpus 2. Carpal Flexors - flex carpus 3. Digital extensor - extend the digits 4. Digital extensors - flex the digits

Question 45

Describe the quadriceps femoris

Answer 45

Found on cranial aspect of proximal hindlimb | Extends the Stifle

Question 46

Name the 4 muscles that make up the quadriceps femoris

Answer 46

Vastus lateralis Vastus medialis Vastus Intermedius Rectus Femoris

Question 47

Name and describe the 3 muscles in the hamstring group

Answer 47

1. Biceps femoris - extends hip and hock - flexes stifle 2. Semitendinosus - extends hip and hock - flexes stifle 3. Semimembranosus - extends the hip and flexes the stifle

Question 48

Name 2 other muscles that attach to the femur

Answer 48

Pectineus -adducts the limb Gastrocnemius -extends hock, flexes stifle

Question 49

What is the action of the cranial tibialis and where is it found?

Answer 49

Found between tibia and tarsus Rotates foot laterally flexes hock

Question 50

What muscle run through the Biceps femoris?

Answer 50

Sciatic nerve