Bone Physiology

What is the bone issue most commonly found in young animals?

Bone development issues

What is the bone issue most commonly found in old animals?

Bone fractures

What are the four sections of the head?

• Cranium

• Maxilla

• Mandible

• Hyoid apparatus

What are the sutures in the skull?

Fibrous joints, mostly collagen

What is the name of the holes in the incisive bone where the teeth sit?

Alveoli

What bone of the skull does the hyoid apparatus attach to?

The temporal bone

What is the purpose of sinuses?

To moisten and warm air passing through

What kind of sinuses do dogs and cats have?

• Frontal sinuses

• Maxillary sinuses

What kind of sinuses do horses have?

A complex network of sinuses

Why are some sinuses in horses split into two?

Because they are so large

What part of the vertebrae causes the withers?

Spinous process

What is the function of intervertebral discs?

Allows the spine to flex and provides cushioning between vertebrae

Name two reasons why vertebrae may touch.

• An intervertebral disc could puncture

• An intervertebral disc could slip out

What is made when floating ribs fuse together?

The costal arch

Name the 3 hormones responsible for control of calcium present in bones.

• Parathyroid hormone

• Calcitriol

• Calcitonin

Name a bone disease caused by low calcium

• Osteomalacia

• Osteoporosis

What is an osteoblast?

An immature cell that can synthesise osteoid

What is an osteocyte?

Bone cells, essentially osteoblasts that have become trapped by the matrix they produce

What is an osteoclast?

A cell that can break down and remodel bone

In which age group are osteoblasts most common?

Infants

What is the name of the finger-like projections found in lacunae?

Canaliculi

Name the 2 main types of bone

• Compact

• Spongy

Where is compact bone most found?

Areas prone to stress

Where is spongy bone most found?

The ends of long bones and the middle of short/flat bones

What does yellow bone marrow produce?

White blood cells

What does red bone marrow produce?

Red blood cells

Define diaphysis.

The central shaft of a long bone

Define epiphysis.

The end of a long bone

Define metaphysis.

The area between the diaphysis and epiphysis in a long bone, contains the epiphyseal growth plate

What does the diaphysis contain?

Yellow bone marrow

What does the epiphysis contain?

• Red bone marrow

• Cancellous bone

What does the metaphysis contain?

The growth plate

Define ossification

The creation of bone

Explain the process of intermembranous ossification

Occurs within the membrane of the foetus, no cartilage template, osteoblasts lay down bone between 2 layers of fibrous connective tissue.

Explain the process of endochondral ossification

The replacement of a cartilage template with bone, starts in embryo but completes when the animal reaches skeletal maturity.

Where are primary ossification centres found?

The diaphyses of bones

Where are secondary ossification centres found?

The epiphyses of bones

Explain what happens at primary ossification centres

Cartilage on the side of the diaphysis side of the growth plate are steadily converted to bone, osteoclasts remodel the interior and create the medullary cavity.

Explain what happens in secondary ossification centres.

• Growth plate produces new cartilage cells on the epiphysis side

• Bone elongates at either side

• Once the bone has reached its full length the cartilage is ossified

• The growth plate is closed in

What are the 3 types of joints?

• Fibrous

• Cartilaginous

• Synovial

Give an example of where you find fibrous joints.

As sutures in the skull

What are the 2 types of cartilaginous joints and where do you find them?

• Synchondroses - between epiphyses and diaphyses in growing animals

• Symphyses - between the mandible bones in the jaw

Give an example of where you find synovial joints.

Ball and socket joints e.g. the shoulder

What 2 things make up the joint capsule?

• Synovial layer

• Fibrous layer

What is synovial fluid?

An ultrafiltrate of blood

Define flexion.

Bending the limb by decreasing the angle of the joint

Define extension.

Straightening the limb by increasing the angle of the joint

Define adduction.

Moving the limb distal to the joint towards the midline

Define abduction.

Moving the limb distal to the joint away from the midline

Define gliding.

Flat surfaces moving over each other

Define rotation.

Turning the limb round its long axis

Define circumduction.

Moving one end of a bone in a circular motion

Define protraction.

Lengthening the limb by moving distal limb away from the body

Define retraction.

Shortening the limb by moving the distal limb towards the body

Define supination.

Turning the palmar/plantar surface more cranially

Define pronation.

Turning the palmar/plantar surface more caudally

What are ligaments mostly made of?

Elastic fibres

What are tendons mostly made of?

Collagen fibres

What is the synovial sheath?

A connective tissue layer surrounding tendons, prevents the bone from rubbing on the tendon

What is the synovial bursa?

A sac sitting between a tendon and bone that acts as a cushion, made up of a synovial membrane full of synovial fluid

What is the meniscus?

Cartilage that acts as a shock absorber

What is the stay apparatus?

Adaptations found in horses which allow the horse to rest and sleep in a standing position

How does the stay apparatus work?

The patella tendon hooks onto the medial epicondyle

What is the equivalent of the suspensory ligament in dogs and cats?

The suspensory muscle

What is the purpose of annular ligaments?

They help to attach the tendons onto bones

What is the origin point?

Where the tendon starts, proximal to the body

What is the insertion point?

Where the tendon attaches to the bone, distal to the body

Define sarcomere.

The functional unit of a muscle cell

How do sarcomeres contract?

The actin hooks onto the myosin and pulls towards the centre, requires calcium and ATP

What are myofibrils?

A bunch of sarcomeres

What is the sarcolemma?

The cell membrane of a muscle cell

What region is covered by the latissimus?

• Starts at the cranial thorax

• Spans along lateral side

• Attaches onto back

What causes the twitch reflex?

The latissimus

What are the flexors and extensors in forelimbs?

Everything cranial is a flexor, everything caudal is an extensor

What are the flexors and extensors in forelimbs?

Cranial muscles extend digits and flex tarsus, Caudal muscles flex digits and extend tarsus