ANSWERS

1. Name the 3 types of muscle tissue and state where each is found.
   • Skeletal muscle (also known as striated or voluntary muscle) - found attached to the bones.
   • Smooth muscle (also known as involuntary muscle) - found throughout the body e.g. within the bowel, bladder and uterus.
   • Cardiac muscle - found only within the heart.
2. Describe the structure of skeletal muscle.
   Composed of fibrous cells which lie parallel to one another in bundles. These bundles are bound together by connective tissue. The whole muscle is made up of groups of these bundles surrounded by a sheath of connective tissue.
3. What is another name for protraction?
   Cranial draw.
4. What is another name for retraction?
   Caudal draw.
5. What is meant by adduction?
   The entire lower limb is brought nearer to the midline.
   NB. Abduction describes the movement of the entire lower limb further from the midline.
6. What is the main difference between isotonic and isometric contraction?
   Isotonic contraction occurs when the ends of the muscle are brought closer together and thus produce movement, whereas isometric contraction is that which occurs when the muscle is tensed but not shortened (e.g. when an animal is standing).
7. What shape are smooth muscle cells?
   Spindle-shaped.
8. What shape are cardiac muscle cells?
   Short and cylindrical.
9. Name the 2 types of muscle fibre.
   • Myosin (thick).
   • Actin (thin).
10. How does a muscle physically contract?
    • The muscle fibres are stimulated by a nervous impulse.
    • The attachments between myosin and actin break and reform sliding along side one another and thus shortening the muscle fibre.
11. What is meant by a motor unit?
    All the muscle fibres that are activated by a single nerve fibre. Muscles capable of performing large movements have large motor units consisting of many fibres (200 or more) innervated by a single nerve fibre.
12. How is skeletal muscle contraction controlled?
    • Via nervous pathways from the brain, down the spinal cord to the muscle groups.
    • Receptors in the muscles and tendons measure the length and tension of a muscle fibre.
13. What is meant by muscle tone?
    A slight state of tension.
14. What is the difference between muscular atrophy and hypertrophy?
    Atrophy occurs as a result of the lack of use of a muscle and the fibres become weak and reduced. This is why physiotherapy is important in recumbent animals. Hypertrophy is the opposite and occurs when a muscle receives constant vigorous exercise. The muscle subsequently becomes larger.
15. What is the main difference between intrinsic and extrinsic muscles?
    Intrinsic muscles lie completely within one region of the body and alter the position of parts of that region, whereas extrinsic muscles run from one body region to another and alter the position of one region in relation to another.
16. Give 2 examples of movements controlled by intrinsic muscles.
    • Closing an eye.
    • Bending the spine.
17. Give 3 examples of movements controlled by extrinsic muscles.
    • Turning the head.
    • Pulling a limb forward.
18. List the 5 categories which together comprise the muscles of the head.
    • Muscles of facial expression.
    • Muscles of mastication.
    • Muscles of the eye.
    • Muscles of the tongue, pharynx, larynx and soft palate.
    • Extrinsic muscles of the head.
19. List 4 movements controlled by the muscles of facial expression.
    • Twitching an ear.
    • Wrinkling the nose.
    • Snarling.
    • Opening or closing an eye.
20. List the 4 main muscles of mastication and state the function of each.
    • Digastricus - opens the jaw.
    • Temporalis - closes the jaw.
    • Masseter - closes the jaw.
    • Medial and lateral pterygoids - move the lower jaw from side to side.
21. What are the names of the muscles which allow dorsal, ventral and lateral movement of the eye?
    The medial, lateral, dorsal and ventral rectus.
22. What is the function of the dorsal and ventral oblique muscles of the eye?
    They allow rotary movement.
23. What is the name of the muscle which enables the eye to be drawn back into its socket and moves the third eyelid?
    The retractor oculi.
24. The muscles of the vertebral column are divided into 2 groups. Name them.
    • The epaxial muscles - situated above the vertebral column.
    • The hypaxial muscles - situated below the vertebral column.
25. List the 4 main structures to which the epaxial muscles are attached.
    • Pelvis.
    • Sacrum.
    • Vertebrae.
    • Ribs.
26. Why are the epaxial muscles more bulky than the hypaxials?
    The epaxials are involved in the support and movement of the spine, head, neck and tail and therefore are under more strain than the hypaxials which are predominantly concerned with movement (such as flexion of the spine and neck) rather than support.
27. Name the muscles of the thorax which play an important role in respiration.
    The internal and external intercostals.
28. The diaphragm separates the thoracic from the abdominal cavity. Can you name the 3 parts of which it is comprised?
    • Peripheral (outer) muscle.
    • Central tendon.
    • 2 Muscular crura (the right crus is larger than the left).
    NB. Crus is simply a term to describe a "leg-like" part.
29. List the 3 holes where structures are able to pass through the diaphragm. In addition to listing the holes, can you name the structure/s which pass through each?
    • Post-caval foramen - posterior vena cava.
    • Oesophageal hiatus - oesophagus and vagal nerves.
    • Aortic hiatus - aorta, azygous vein and thoracic duct.
30. List the 4 muscles on each side of the body which together comprise the abdominal wall.
    • External abdominal oblique.
    • Internal abdominal oblique.
    • Transversus abdominis.
    • Rectus abdominis.
31. What is the name of the area where the aponeuroses of the abdominal muscles join at the ventral midline?
    The linea alba (white line).
32. Name the 4 main extrinsic muscles of the forelimb, and briefly describe the location and function of each.
    • Trapezii - runs from spine of scapula to dorsal midline - supports the limb on the body.
    • Brachiocephalicus - runs from anterior humerus to base of skull - bends neck or protracts (brings forward) forelimb.
    • Latissimus dorsi - runs from humerus to dorsal midline - retracts (brings backward) forelimb.
    • Pectorals - run from humerus around front of thorax to sternum and ribs - hold forelimb in close to the body (adduction).
33. Name the 2 muscles of the shoulder.
    • Supraspinatous - extends shoulder.
    • Infraspinatous - flexes shoulder.
34. There are 2 muscles involved in the flexion of the elbow. Name them.
    • Biceps brachii.
    • Brachialis.
35. What is the name of the muscle which extends the elbow joint?
    The triceps.
36. What 3 joints are affected by the hamstring muscle group?
    • Hip.
    • Stifle.
    • Hock.
37. List the 3 members of the hamstring muscle group.
    • Biceps femoris.
    • Semitendinosis.
    • Semimembranosis.
38. What is the name of the muscle which extends the stifle?
    The quadriceps femoris.
39. What is the main flexor muscle of the hock?
    The cranial tibial.
40. What is the main extensor muscle of the hock?
    The gastrocnemius.
41. Name the 3 muscles which make up the adductor group on the inside of the thigh which hold the limb in towards the body?
    • Adductor.
    • Gracilis.
    • Pectineus.
42. What is the difference between a ligament and a tendon?
    A ligament joins bone to bone, whilst a tendon joins muscle to bone.
43. What is the name of the ligament which holds the head of the femur within the acetabulum?
    The round ligament.
44. Name the ligaments which stabilise the stifle joint.
    • The cruciate ligaments - these run from the tibia to the femur and prevent the bones from sliding forward and back on one another.
    • The collateral ligaments - these prevent sideways movement of the joint.
45. What is the name given to a flat, fibrous sheet of tendon?
    An aponeurosis.
46. Describe the location and composition of the Achilles tendon.
    This runs down the back of the shank, over the point of the hock and then down towards the digits. It comprises the tendons of the superficial digital flexor, gastrocnemius, biceps femoris and semitendinosis and subsequently has more than one point of insertion.
47. Define the following: bursa, acquired bursa and synovial sheath.
    • Bursa - a synovial fluid filled cavity which lies between tendons or between tendon and bone to minimise friction between the structures as they move backwards and forwards.
    • Acquired bursa - found predominantly on the bony prominences (hocks and elbows) of large or elderly dogs which habitually lie on hard surfaces; these form to provide protection from friction with the ground.
    • Synovial sheath - a bursa which completely surrounds a tendon.