AB1 Learning Objectives

Explain the function of the skeleton

Support - internal structures and head

Locomotion/movement - spine and limbs

Protection - of organs by bone (e.g. skull, chest wall)

Storage of minerals - esp. calcium and phosphorous

Blood synthesis (haematopoiesis) - in bone marrow

Axial definition

Refers to skull, ribs and sternum, and vertebral column. Contains bone down the central axis.

Appendicular definition

Refers to limbs (fore and hind)

Heterotopic (splanchic) Skeleton definition

Refers os penis/baculum

Features of fibrous joints

Dense connective tissue, very little movement (e.g. skull suture). Tends to be more flexible in younger animals while growing more rigid as animal matures.

Features of cartilaginous joints

Cartilage, some movement (e.g. mandibular symphasis)

Features of synovial joints

Joint cavity with fluid; joint capsule and ligaments; sometimes contain fibro-cartilaginous pads and menisci - help conformation; a great deal of movement (e.g. elbow).

Cranial

towards head

Caudal

towards tail

Proximal

towards attached end

Distal

towards back

Ventral

towards belly

Dorsal

towards back

Palmar

caudal (below carpus)

Plantar

caudal (below tarsus)

Medial

towards median plane

Lateral

away from median plane

Rostral

towards nose

Axial/abaxial

towards or away from a plane or axis

Oral

towards mouth

Aboral

away from mouth

Composite use of terms

order indicates the direction of travel. Ex: mediolateral would have outside of body touching x-ray plate with middle facing up.

Protraction

cranial movement of the limb ex: reaching out with arm

Retraction

caudal movement of the limb (as when drawing an arm back)

Flexion

Reduces angle between two bones across a joint (bends the limb)

Extension

increases angle between two bones across a joint (straightens the limb)

Abduction

Move limb away from median plane or away from the body trunk. Think of when someone is abducted they are taken away.

Adduction

Move limb towards median plane or towards body trunk

Circumduction

Movement of the limb describes a circle at the distal extremity. If you point to the floor and describe a circle with your extending index finger, you are circumducting your arm.

Rotation

Movement of limb or structure around its own long axis (limbs can undertake internal or external rotation). This movement takes place when you turn a door knob.

Supination

Lateral rotation of appendage so that palmar/plantar surface of paw faces medially (like holding bowl of soup). Not as common in vet med.

Pronation

Medial rotation from supine position so that palmar/plantar surface will face the floor

Flexure angles

The side of the joint at which flexion takes place (usually cranial or caudal). Alternates as you go down the limb.

Origin

Proximal, dorsal, cranial or central attachment point.

Insertion

distal, ventral, caudal, or peripheral attachment point

Agonist

brings about action. opposite of antagonist.

Antagonist

brings about opposite action to agonist.

Skeleton of the head

Consists of the skull, mandible, hyoid bones, and the ear ossicles (malleus or hammer, incus or anvil, and stapes or stirrup)

Brachycephalic

short headed

Mesaticephalic

medium headed

Dolichocephalic

long headed

Dental formula of adult dog

I 3/3 C 1/1 PM 4/4 M 2/3 = 42 total

Dental formula of adult cat

I 3/3 C 1/1 PM 3/2 M 1/1 = 30 total

Features of normal anatomical bite/occlusion in dog

1. Upper incisors rostral to lower

2. Lower canines in front of upper, evenly in space between last incisor and upper canine

3. Premolar interdigitation (zigzag)

4. Upper molars rest outside of lower molars in the closed mouth

Structure and function of suture joints in skull

Skull bones formed by intramembranous ossification, resulting in a fibrous joint when the advancing bones meet. As animal ages, suture joint ossifies but irregularly. Allows skull to flex during growth while providing stabilization and protection in later years.

Structure and function of mandibular symphysis joint in skull

Fuses hemi-mandibles in horses, while fibrocartilaginous joint in carnivores and ruminants attaches the two hemi-mandibles. Horses do not need flexibility due to their diet of thick grasses while other species need a flexible joint to absorb heavy chewing stress. Often seen in animals hit with cars where symphysis becomes separated, can be fixed by wiring the hemimandibles together or using dental composites.

Structure and function of temporo-mandibular joint (TMJ) in skull

Classified as a condylar synovial joint with the articular surface of the egg shaped mandible fitting into the concave shaped temporal bone. Allows for opening (extension) and closing (flexion) of the jaw. Often seen dislocated in cats who have fallen, can be difficult to relocate due to high barriers of temporal bone.

Axial skeleton

Includes skull (not mandible), vertebral column, and ribs and sternum.

Appendicular skeleton

Fore and hind limbs

Heterotopic skeleton

os penis in male dogs

Average total number of bones in male and female dogs

134 (axial) + 186 (appendicular) + 1 (splanchnic in males) = 321 in male and 320 in female dogs

Number and type of ribs in dogs

13 total in dogs and cats with 9 sternal (true) and 4 asternal (false) ribs.13th rib floats.

Number of sternebrae in dogs

8 total sternebrae. S1 = manubrium, S2-7 = body, S8= xiphoid process.

Manubrium

S1 and most cranial segment of the sternum. Shaped like a handle.

Xiphoid process

S8 and most caudal segment of the sternum. Small and pointed.

Number and types of vertebrae making up vertebral column in dogs

Around 50 total in dogs and cats.

Vertebral formula: Cranial (C) 7, Thoracic (T) 13, Lumbar (L) 7, Sacral (S) 3, Coccygeal (Cd) 20-23

Key features of cervical vertebra

Key features of thoracic vertebra

Key features of lumbar vertebra

Key features of sacral vertebra

Key features of coccygeal vertebra

Functional anatomy of the vertebral column

Structure and function of intervertebral discs