Locomotion 2

All lectures included (except some spinal + abdominal), practicals to add

What is the name of the equine 3rd metacarpal?

Cannon bone

What sesamoid bones are present in the horse manus?

2 proximal sesamoid bones and the navicular

What is the name of the equine P1?

Long pastern

What is the name of the equine P2?

Short pastern

What is the name of the equine P3?

Coffin or pedal bone

Where is the navicular bone?

Between the distal and medial phalanges, in the deep digital flexor

Where are the proximal sesamoid bones?

Caudal to the distal cannon bone, in the interosseus

What is the equine MCPj called?

Fetlock joint

What is the name of the equine PiPj?

Pastern joint

What is the name of the equine DiPj?

Coffin joint

What ligaments are present in the equine manus?

MCPj, PiPj and DiPj collaterals; short collateral of PSBs; interosseus; collateral of navicular and impar, and axial and abaxial palmar.

How does the interosseus divide from the proximal sesamoids?

Extensor slips to extensor tendon, inter-sesamoidean, cruciate and deep, oblique, and straight

Where are the collateral ligaments of navicula?

Connected to the navicular bone, proximally connecting to the long pastern

Where is the navicular bursa?

Superficial to the navicular bone

Where is the impar ligament?

Distal to the navicular bone, connected to the coffin bone

What annular ligaments are present in the horse manus?

Palmar (between proximal sesamoids), proximal palmar digital (on long pastern), distal palmar digital (on short pastern)

What ligament travels from the distal palmar digital annular ligament to the skin?

Ligament of ergot

What ligaments travel down form the equine antebrachium to manus?

SDF, DDF, and CDE/long DE

Where does the SDF insert?

On proximal P2

Where does DDF insert?

On caudal P3, after passing around the navicular bursa

How many navicular and proximal sesamoids does a ruminant have?

2 and 4

What are the mechanical theories behind navicular disease?

Damaged by compression due to weight bearing (weight passed onto heels), or due to redirection of DDF

What is the vascular theory of navicular disease?

the navicular bone is supplied blood by delicate blood vessels that may become damaged

Where do the blood vessels of the navicular bone come from?

Plexi come from the palmar artery of P2 and from palmar digital artery as it approaches the distal palmar arch

What is involved in the forelimb stay apparatus?

Suspensory ligament (interosseus) prevents MCPj overextension

Palmar ligg. prevent PiPj overextension

Carpal and radial check ligg. prevent overextension of interphalangeal joints

Carpal bones ‘lock’ in a straight line 

Elbow snap joint, aided by fibrous old pronators

Biceps tendon of origin ‘sticks’ in bicipital groove

Trunk is ‘slung’ on relatively fibrous serratus ventralis

Lacertus fibrosus to prevent shoulder flexion when carpus + elbow locked?

What is involved in the hindlimb stay apparatus?

Accessory ligament (pelvis→femur) prevents abduction

SDF contains a fibrous band from femur to tuber calcis

Suspensory lig. and tarsal check ligament

Hock snap joint

What makes up the reciprocal apparatus?

SDF until insertion on tuber calcis, peroneus tertius

What regions are present in hoof/claw?

Wall, sole and pad

What parts of the horse foot are insensitive?

the keratin horn of the hoof wall, sole and frog

Where does the the hoof wall form?

at the coronary papillae

Where does pigmented horn form

at the perioplic papillae

Where does the sole horn form?

at the solar papillae

What are hoof papillae?

Projections of the dermis

What strata are present in wall horn?

internum, medium and externum/tectorium

How does wall horn reach the floor?

By sliding of laminae

What types of laminae exist?

Sensitive and insensitive, primary and secondary (no secondary in oxen)

How do lamellae move?

desmosomes between primary and secondary lamellae break and reform, so secondary move down primary

How are lamellae visible on a live horse?

As the white line

Endocrine causes of laminitis

Obesity, steroids/Cushing’s, hyperinsulinaemia

Non-endocrine causes of laminitis

Sepsis, continual excess pressure

How can the frog move?

The central sulcus and crura can widen and narrow to accommodate weight bearing

How should the frog be positioned in a healthy standing hose

Just touching the floor

What are ungual cartilages made of?

Hyaline cartilage, which ossifies with age

What cushions are related to the equine hoof?

digital cushion proximal to frog, coronary cushion

What shape is a donkey hoof?

U-shaped, often “broken forward”, cylindrical

Where is the weight borne in an ox hoof

On sole and heel

Where is the hoof wall thinnest in ox hoof?

Axially

What cushion is present in the oxen hoof?

Coronary cushion

Which claw is largest in oxen?

The lateral claw

How are cat claws bared and retracted?

Bared actively by taut PiPj and MCPj and pull on DDF.

Retracted passively by axial and abaxial dorsal elastic ligaments

What pads are present in carnivores?

5/4 digital, 1 metacarpal/1 metatarsal, 1 carpal/0 tarsal

What pads are present in rabbits?

None

What are the metacarpal and carpal/tarsal pad equivalent in ungulates?

Ergots and chestnuts

Which limb bud forms first?

The forelimb bud

What does the limb bud form from?

The somatic lateral plate mesoderm

What migrates into the limb bud after it forms? What doesn’t?

Muscle, vessel and nerve precursors.

Skeletal and tendon precursors are already present.

What limb bone does not form by endochondral ossification

Blade of the scapula

What mediates proximo-distal diff. in a limb bud?

The apical ectodermal ridge

What can go wrong with proximodistal differentiation in a limb bud?

AER ablation causes loss of elements

What controls caudo-cranial patterning in a limb bud

The zone of polarising activity

What can go wrong to cause polydactyly?

Ectopic expression of ZPA-related genes

How do individual digits form?

By apoptosis of the tissues between them

What is the process of endochondral ossification split into?

Blastemal condensation

Chondrification

Hypertrophy and appositional growth

Early mineralisation

Vascular invasion

Lengthening of diaphysis

Formation of secondary centres in epiphyses

What happens in blastemal condensation?

Mesenchyme cells condense to correct positions

What happens in chondrification?

Cells differentiate into chondrocytes, cartilage model forms

What happens in hypertrophy in bone development?

Chondrocytes at the centre of the model stop developing and swell.

How does appositional bone growth occur?

The connective tissue around the model compresses to form perichondrium. Inner surface of perichondrium deposits cartilage 

Where does early mineralisation occur?

In the centre of the cartilage model due to chondrocytes, at cortical bone collar as perichondral osteoblasts develop

How doe vascular invasion of bone occur

Vessels puncture cortical bone, bringing in osteoblasts. Osteoblasts then form primary spongiosa.

What happens as the diaphysis lengthens?

Chondrocytes undergo proliferation and hypertrophy, marrow cavity enlarges.

What happens to form secondary centres in the epiphyses?

Chondrocyte hypertrophy, vascular invasion, ossification

As epiphyses grow, how is the diaphysis affected?

Traction on periosteum due to epiphysis growth causes more bone to be deposited

What zones exist in a growth plate?

Reserve hyaline cartilage,

Proliferation,

Maturation,

Hypertrophy and calcification,

Cartilage degeneration and osteoblast invasion,

Osteogenic

Which growth plates are present in a foal’s digits?

One per bone, at the end nearest the fetlock

What types of growth plates exist?

Under compression, under tension, flake epiphyses, atavistic

What causes angular limb deformities?

Damage to a growth plate, so one of a pair of bones stops growing

What types of Salter-Harris fractures can happen

Straight across

Above

Lower

Through Everything

cRush

Where do osteosarcomas usually form?

In prior growth plates, especially near the stifle or away from the elbow.

How do joints form?

A mesenchyme joint plate forms, cavitates and differentiates into capsule and synovial membrane. Synovial cells on articular surfaces are worn away in utero.

How does proximal and distal joint formation differ?

Proximal joint plates form in gaps between bones, interphalangeal joint plates split bones

What sections does the myotome divide into?

Epimere and hypomere

What does epimere form?

Dorsal vertebral muscles

What does the hypomere form?

Ventral vertebral muscles, limb muscles, body wall muscles

What structures formed as the notochord evolved into vertebrae?

Gel-like notochord

Centra with associated neural or haemal arches or ribs

Composite vertebrae

What movements doe the spine carry out?

Sagittal plane flexion and extension

Frontal plane flexion

Axial rotation

How do vertebrae form?

From sclerotome, by endochondral ossification. 

Where are the ossification centres of vertebrae?

Primary: inside centrum, cranial and caudal epiphyses of centrum

Appositional: around model of laminae

Secondary: sometimes in processes

How many vertebrae does a ruminant have?

7C, 13T, 6L, ~5S, ?Cd

How many vertebrae does a cat/dog have?

7C, 13T, 7L, ~3S, ~20Cd

How many vertebrae does a pig have?

7C, 5/14T, 6/7L, ~4S, ?Cd

How many vertebrae does a horse have?

7C, 18/19T, 6L, ~5S, ?Cd

What numbers of vertebrae can rabbits have?

7C, 12T, 7L, 3S

7C, 13T, 6L, 3S

7C, 13T, 7L, 3S

Where does nerve C1 exit the spine?

Through lateral foramen

How does the skull-C1 joint move?

In the medial plane

How does the C1-C2 joint move?

In the lateral plane

How are C3-7 shaped?

Short neural spines, two-pronged transverse processes

How does the vertebral artery travel along the neck.

Through the transverse foramina of C1-6

How are thoracic vertebrae shaped?

All have very short transverse processes to articulate with ribs. Long neural spines cranially, shorten to blend in with lumbar vertebrae caudally

How are lumbar vertebrae shaped?

Long transverse processes (directed laterally in large animals, ventro-cranio-laterally in small animals)

How are horse lumbar vertebrae unusual?

Joined by inter-transverse synovial articulations