Bones of the Appendicular skeleton

what are the two types of bone formation?

1. endochondral ossification

2. intramembranous

What is endochondral ossification?

mesoderm --> hyaline cartilage model --> bone

Mesenchyme is replaced with cartilage (chondroplast cells). The cartilage framework is then replaced with bone.

How many ossification centers are there during ossification?

there is one primary ossification center and the rest are secondary.

What is the nutrient foramen?

a small opening in the shaft of a bone that allows blood vessels to supply nutrients and aid in the growth of the bone. It is the main source of nutrients for long bones.

What is intramembranous ossification?

The mesoderm bypasses the cartilaginous stage and directly forms the bone (this is present in the flat bones of the skull)

What are the parts of a long bone?

Proximal/distal epiphysis, proximal/distal metaphysis, diaphysis, and physis

What is the metaphysis?

the wide, rapidly growing ends of the diaphysis. It is between the diaphysis and the physis

what is the physis?

a plate of growing cartilage that separates the shaft (metaphysis) from the epiphysis. At maturity, the physeal cartilage ceases to grow.

What is epiphyseal cartilage?

the cartilage on the articular surface of the epiphysis. This cartilage remains even into adulthood.

What is an ununited anconeal process (UAP)?

the failure of fusion of the anconeal process with the ulna after 5 months of age.

what is the function of the thoracic limb?

support

What bones make up the thoracic limb?

scapula, humerus, radius and ulna, manus

True/false- the thoracic limb has a bony connection to the axial skeleton

FALSE- there is no bony articulation with the axial skeleton (AKA synsarcosis = attached by muscles)

what bones make up the pectoral/thoracic girdle?

Scapula and clavicle

What is the function of the pelvic limb?

Propulsion

What bones make up the pelvic limb?

os coxae, femur, tibia and fibula, pes

true/false- the pelvic limb has bony attachment to the axial skeleton

TRUE- it connects to the axial skeleton through the sacroiliac joint

What bones make up the pelvic girdle?

ossa coxarum + sacrum + first coccygeal vertebra

What are the four regions of the thoracic limb?

1. scapular region

2. brachium

3. antebrachium

4. manus

What makes up the scapular region of the thoracic limb?

the scapula

what makes up the brachium in the thoracic limb?

the humerus

What makes up the antebrachium in the thoracic limb?

radius and ulna

what makes up the manus of the thoracic limb?

carpal, metacarpal, and phalangeal regions

What is sweeny?

The muscles covering the scapula will atrophy and the spine of the scapula will be visible.

• in horses?

True/false- cats have clavicles

True- they can often be mistaken for a bone in the esophagus on lateral radiographs

what is the clavicle like in the dog?

it is represented by fibrous clavicular intersection in the brachiocephalicus muscle

The head of the humerus is involved in what joint?

it articulates with the glenoid cavity to form the shoulder j.

What is the function of the deltoid tuberosity?

attachment site for the deltoideus M.

the humeral condyle is involved in what joint?

it articulates with the radius and ulna to form the elbow j.

What structure is present on the humerus of the dog only?

the supratrochlear foramen

What passes through the supratrochlear foramen?

NOTHING

What structure is present on the humerus of the cat only?

supracondylar foramen

What passes through the supracondylar foramen?

brachial A. and median N.

The head of the radius in involved in what joint?

it articulates with the humerus to form the elbow j.

The distal extremity of the radius is involved in what joint?

it articulates with the carpal bones and ulna (in carnivores) to form the antebrachiocarpal j.

What is the purpose of the three cranial grooves on the radius?

they are for extensor tendons

true/false- the ulna is weight-bearing

FALSE- it just serves for muscle attachment and formation of the elbow and carpal joints

true/false- animals with a fused radius and ulna are unable to supinate/pronate

TRUE- the radius and ulna must be unfused for them to be able to supinate/pronate

How many interosseous spaces are present in the fused horse radius/ulna?

ONE- proximal interosseous space

how may interosseous spaces are present in the fused ox radius and ulna?

TWO- proximal and distal interosseous spaces

How many carpal bones are there and how are they arranged?

seven arranged into two rows (proximal and distal)

What is the only carpal bone that has muscle attachment?

the accessory carpal bone

how is the distal row of carpals counted?

from medial to lateral

How are the metacarpals counted?

medial to lateral

How many phalanges does each digit have?

3 (except for the first digit which only has the first and third)

How many sesamoid bones are there in the dog manus?

at the metacarpophalangeal j. there are three: 1 dorsal and 2 palmar (except the first digit only has 2: one palmar and one dorsal)

What digits are weight-bearing in the dog?

4: Mc 2, 3, 4, and 5

What digits are weight-bearing in the pig?

2: Mc 3 and 4

How many digits are weight-bearing in the ox?

2: Mc 3 and 4 (fused to form the cannon bone)

• 5 are reduced

• sesamoid bones dew claws behind fetlock

How many digits in the horse are weight-bearing?

1: Mc 3 (cannon bone)

• 2,4 reduced as splint bones

What bones make up the os coxae?

ilium, ischium, pubis, and acetabulum

• unite around the acetabulum

The head of the femur is involved in what joint?

it articulates with the acetabulum to form the hip j.

The ilium is involved in what joint?

The auricular surface of the ilium articulates with the sacrum to form the sacroiliac j.

The condyles of the femur are involved in what joint?

The femoral condyles articulate with the tibial condyles to form the stifle j.

true/false- the fibula is weight-bearing

FALSE- the tibia is weight-bearing

How many tarsal bones are present in the dog and how are they arranged?

7 bones in three rows- two proximal, one in the middle row, and four in the distal row

Species differences in the Greater tubercle of the humerus

lateral, next to head & point of shoulder

• OX - BIG overhang groove, very (most) prominent

• Horse - smaller than ox

Deltoid tuberosity in Horses/Ox

More prominent than in the cat/dog

Equine ulna

Rudimentary

medial styloid process

In Radius

medial styloid process is the most distal part (tip)

(lateral) styloid process

In ulna

Obturator foramen

• large opening bounded by pubis and ischium. has muscles in real life.

Pelvic symphysis

• joint between right and left os coxae halves.

• Comrpised of pubic symphysis + ischial symphysis

ilium

• most cranial, comprised of wing and body/shaft

• Has a auricular surface

  • ear shaped, articulates with sacrum/sacroiliac joint

Ischium - caudal part of hip bone

• ischial tuber = caudal most part of pelvic symphysis

• Has 2 depressions

greater trochanter

• VERY LARGE, proximolateral extremity

Third trochanter

In Horses and Dogs

• Very prominent in Horses, tiny in dogs

What is the censored structure?

Femoral / gluteal tuberosity

tibial tuberosity

• cranial projection for patellar ligament

cochlea

• distal articular surface

medial malleolus

• non articular, sharp prominence

flat head

• articulates with lateral tibial condyle

Fibula body - complete in carnivores

lateral malleolus

• distal projection

Tibia + Fibula comparative: Horses

fused fibula, rudiment seen proximally

Tibia + Fibula comparative : Ox

1. absent fibula, head and distal remnant seen

   1. distal remnant named MALEOLAR BONE

Tarsus

Arranged in 2.5 or 3 rows

1. 7 bones. 2 proximal, 1, 4 distal

2. calcaneus is lateral

Metatarsus

4 bones

1. RUMINANTS

   1. cannon bone = 3+4 fused. MT 5 absent unlike MC 5

   2. instead MT 2 is present and called METATARSAL SESAMOID BONE (medial)

Distal interphalangeal joint name in horses

Coffin bone