Skeletal system - All the bones

Axial Skeleton

• The thorax is formed by the thoracic vertebrae and the ribs
• The heads of the ribs form joints with the thoracic vertebrae, which are freely movable to help with ventilation
• The ventral ends of the ribs have two parts: a dorsal part made of bone and a ventral part made of cartilage (costal cartilage)
• The costal cartilages join the sternum directly or join the costal cartilage ahead of them

Sternum

• Also known as the breastbone
• Forms the floor of the thorax
• Made up of bones called sternebrae
• Only the first and last sternebrae are named and used as landmarks, the rest are numbered
• The most cranial sternebra is the manubrium, and the most caudal is the xiphoid or xiphoid process

Appendicular Skeleton

• Made up of the bones of the limbs (thoracic and pelvic limbs)
• Thoracic limb:
  • Scapula: most proximal bone of the thoracic limb, flat, triangular with a prominent longitudinal ridge on its lateral surface
  • Humerus: long bone of the upper arm, proximal end forms the ball-and-socket shoulder joint, distal end forms the elbow joint with the radius and ulna
  • Radius and ulna: form the antebrachium (forearm), part of the elbow joint with the distal end of the humerus
  • Carpal bones: form the wrist joint
  • Metacarpal bones: form the metacarpus
  • Phalanges: form the digits of the thoracic limb
• Pelvic limb:
  • Femur: long bone of the thigh, proximal end forms the ball-and-socket hip joint, distal end forms the stifle joint with the patella and tibia
  • Patella: largest sesamoid bone in the body, forms in the distal tendon of the quadriceps femoris muscle, helps protect the tendon as it passes over the trochlea of the femur
  • Tibia: main weight-bearing bone of the lower leg, proximal end forms the stifle joint with the femur, distal end forms the hock joint with the tarsus
  • Fibula: thin bone that parallels the tibia, serves as a muscle attachment site
  • Tarsus (hock): forms the ankle joint, consists of two rows of short bones (tarsal bones)
  • Metatarsus: forms the metatarsus, similar to the metacarpal bones
  • Phalanges: form the digits of the pelvic limb

Visceral Skeleton

• Consists of bones that form in soft organs or viscera
• The os penis is a bone in the penis of dogs that partially surrounds the penile portion of the urethra

Tarsus (Hock)

• Consists of two rows of short bones (tarsal bones)
• Proximal row of bones is named, and the distal row is numbered (from medial to lateral)
• Tibial tarsal bone and fibular tarsal bone are the largest proximal bones
• Tibial tarsal bone has a large trochlea that articulates with the distal end of the tibia to form the most movable part of the hock joint
• Calcaneal tuberosity of the fibular tarsal bone projects upward and backward to form the point of the hock
• Acts as the point of muscle attachment and corresponds to our heel

Metatarsus

• Almost the same as the metacarpal bones
• Main difference is that there are usually only four digits making up the paw on the hindleg, so only four metatarsal bones (II to V, no "dew claw" or metatarsal I)
• In humans, these are the bones of our feet

Phalanges

• The phalanges of the pelvic limb are almost exactly like the phalanges of the thoracic limb
• The only major difference is that usually only four digits make up the paw on each hind leg: digits II through V

Visceral Skeleton - Os Penis

• The visceral skeleton consists of bones that form in soft organs or viscera
• It is the strangest division of the skeleton and the most variable
• Not all animals have visceral bones - they are pretty unusual
• Os penis is a bone in the penis of dogs that partially surrounds the penile portion of the urethra
• Urethral groove on the ventral surface of the bone encloses the dorsal portion of the urethra

Recap

• The division of the skeleton that contains the bones mentioned is the appendicular skeleton
• Joints between the bones are movable joints

Pelvis

• Develops as 3 separate bones on each side that eventually fuse into a solid structure
• Two halves are joined ventrally by a cartilaginous joint called the pelvic symphysis
• Pelvis joins the axial skeleton dorsally at the sacroiliac joints (one on each side)
• Though fused, the names of the bones are still used to designate the main regions of the pelvis - ilium, ischium, pubis

Pelvis - Functions

• Weight-bearing from hindlimbs
• Protects and supports the intestines, bladder, and internal sex organs

Pelvis - Ilium

• Most cranial bone of the pelvis
• Projects up in a dorsocranial direction and is the bone that forms the sacroiliac joints with the sacrum
• In dogs and cats, the smooth “wing” of the ilium projects forward and is easily felt as a landmark in living animals

Pelvis - Ischium

• The ischium is the caudal-most pelvic bone
• The main, rear-projecting process of the ischium is the ischial tuberosity

Pelvis - Pubis

• The smallest of the three pelvic bones
• Located medially and forms the cranial portion of the pelvic floor, while the ischium forms the caudal part

Pelvis - Other Notable Structures

• Pelvic/Pubic Symphysis: cartilaginous joint that ossifies with age and joins the two sides of the pelvis together ventrally, facilitating the passage of the foetus through parturition (birth)

Femur

• Long bone of the thigh
• Proximal end:
  • Ball portion of ball-and-socket hip joint called the head of the femur
  • Very deep, secure joint
  • Large processes (e.g. Greater Trochanter) where hip and thigh muscles attach
• Distal end:
  • Forms the stifle joint with the patella and tibia
  • Medial & Lateral condyles (caudal) which articulate with proximal end of fibia
  • Trochlea (cranial) where patella lies
  • Medial and lateral epicondyles are “knobs” that are easily palpated and can be used as landmarks on living animals

Patella

• The patella or kneecap is the largest sesamoid bone in the body
• Forms in the distal tendon of the large quadriceps femoris muscle on the cranial aspect of the stifle joint
• Helps protect the tendon as it passes down over the trochlea of the femur to insert on the tibial crest

Tibia

• Main weight-bearing bone of the lower leg
• Proximally: Forms stifle joint with femur above
• Proximal end appears triangular
• Forward-facing point of the triangle is the tibial tuberosity where the patellar ligament attaches
• Distally: Forms the hock with the tarsus below

Fibula

• A thin bone in dogs and cats that parallels the tibia
• Does not support any significant weight but mainly serves as a muscle attachment site
• At its distal end, the fibula forms a palpable process called the lateral malleolus

Axial Skeleton

• The axial skeleton consists of the skull, hyoid bone, spinal column, ribs, and sternum
• Hyoid bone:
  • Located high in the neck, just above the larynx
  • Supports the base of the tongue, pharynx, and larynx
  • Helps in swallowing
  • Composed of several individual portions united by cartilage
• Spinal Column (Vertebral Column):
  • Divided into five regions: Cervical, Thoracic, Lumbar, Sacral, and Caudal (Coccygeal)
  • Each region has numbered individual vertebrae
  • Vertebrae are separated by intervertebral discs (fibrocartilage)
  • The arch houses the spinal cord
  • Processes are sites for muscle attachment and provide leverage for movement
  • Each vertebra joint allows limited movement, but the whole spine has considerable flexibility

Cervical Vertebrae

• Located in the neck region
• 7 vertebrae in dogs and cats
• C1 = Atlas, C2 = Axis, rest of cervical vertebrae are similar and numbered like the rest of the vertebrae
• Atlas has “Wings of the Atlas” (transverse processes) and holds up the head
• Axis - spinous processes project dorsally, and peg-like “dens” fit into the atlas to form the atlantoaxial joint (allows pivot-like side to side movement)

Thoracic Vertebrae

• Located dorsal to the thorax (chest)
• Animals usually have the same number of pairs of ribs as the number of thoracic vertebrae
• Have very tall, spinous processes
• Lateral facets form joints with the ribs

Lumbar Vertebrae

• Dorsal to abdominal region
• Have large, bulky bodies to support the abdominal contents (compared with thoracic vertebrae, which have the support of the ribs)

Sacral Vertebrae

• Located dorsal to the pelvic region
• Forms a joint with the pelvis on each side called the sacroiliac joint
• Sacral vertebrae are unique in that they fuse to form a single solid structure called the sacrum

Caudal (Coccygeal) Vertebrae

• Form the bones of the tail
• Number and appearance vary greatly between and within a species and even within an individual
• In humans, these are fused to form the coccyx or “tailbone”

Ribs

• Flat bones, form lateral part of thorax
• The number of pairs of ribs usually equals the number of thoracic vertebrae

Sesamoid Bones

• Rarely of clinical significance except in performance dogs and heavy large-breed dogs, such as St. Bernards
• These heavy breeds can fracture sesamoid bones by jumping

Appendicular Skeleton

• Pelvis:
  • Develops as 3 separate bones on each side that eventually fuse into a solid structure
  • Two halves are joined ventrally by a cartilaginous joint called the pelvic symphysis
• Femur:
  • Proximal end: Ball portion of ball-and-socket hip joint called the head of the femur
  • Straight shaft
  • Distal end: Forms the stifle joint with the patella and tibia
• Patella:
  • Largest sesamoid bone in the body
  • Forms in the distal tendon of the large quadriceps femoris muscle on the cranial aspect of the stifle joint
  • Helps protect the tendon as it passes down over the trochlea of the femur to insert on the tibial crest
• Tibia:
  • Main weight-bearing bone of the lower leg
  • Proximally: Forms stifle joint with femur above
  • Distally: Forms the hock with the tarsus below
• Fibula:
  • Thin bone in dogs and cats that parallels the tibia
  • Does not support any significant weight but mainly serves as a muscle attachment site
• Tarsus (hock):
  • Known as the hock in four-legged animals (humans = ankle)
  • Two rows of short bones (tarsal bones)
• Metatarsus:
  • Almost the same as the metacarpal bones
  • The main difference is that there are usually only four digits making up the paw on the hindleg so only four metatarsal bones: II to V
• Phalanges:
  • The phalanges of the pelvic limb are almost exactly like the phalanges of the thoracic limb
  • The only major difference is usually only four digits make up the paw on each hind leg: digits II through V

Visceral Skeleton

• Consists of bones that form in soft organs or viscera
• The os penis is a bone in the penis of dogs that partially surrounds the penile portion of the urethra

Axial Skeleton

• Hyoid bone:
  • Located high in the neck, between the caudal ends of the mandible
  • Supports the base of the tongue, pharynx, and larynx, and helps the animal swallow
  • Composed of several individual portions united by cartilage
• Spinal Column (Vertebral Column):
  • Made up of individual irregular bones (vertebrae)
  • Divided into five regions
  • Individual vertebrae are numbered within each region
• Vertebrae:
  • Made up of the body, arch, and several processes
  • Vertebrae are separated by intervertebral discs (fibrocartilage) - shock absorbers
  • The arch houses the spinal cord
  • Processes are sites for muscle attachment and provide leverage for movement
  • Each vertebrae joint allows limited movement, but the whole spine has considerable flexibility
• Sternum (Breastbone):
  • Forms the floor of the thorax
  • Made up of bones called sternebrae
  • First and last sternebrae are named and used as landmarks, the rest are numbered
  • Manubrium is the most cranial, and xiphoid or xiphoid process is the most caudal

Appendicular Skeleton

• Thoracic Limb:
  • Scapula:
    • Most proximal bone of the thoracic limb
    • Flat, triangular bone with a prominent longitudinal ridge on its lateral surface - the "spine of the scapula"
    • Forms the socket portion of the ball-and-socket shoulder joint
  • Humerus:
    • Long bone of the upper arm (brachium)
    • Proximal end: ball and socket shoulder joint
    • Distal end: elbow joint with radius and ulna
  • Radius and Ulna:
    • Form the antebrachium (forearm)
    • Proximal end: elbow joint with the distal end of the humerus
    • Distal end: articulates with the carpus
• Pelvic Limb:
  • Femur (Thigh Bone):
    • Long bone of the thigh
    • Proximal end: ball portion of ball-and-socket hip joint
    • Distal end: forms the stifle joint with the patella and tibia
  • Patella (Kneecap):
    • Largest sesamoid bone in the body
    • Formed in the distal tendon of the quadriceps femoris muscle on the cranial aspect of the stifle joint
    • Helps protect the tendon as it passes down over the trochlea of the femur to insert on the tibial crest
  • Tibia (Shin Bone):
    • Main weight-bearing bone of the lower leg
    • Proximally: forms stifle joint with femur above
    • Distally: forms the hock with the tarsus below
  • Fibula:
    • Thin bone that parallels the tibia
    • Does not support any significant weight, mainly serves as a muscle attachment site
  • Tarsus (Hock):
    • Known as the hock in four-legged animals (humans = ankle)
    • Two rows of short bones (tarsal bones)

Visceral Skeleton

• Os Penis:
  • Bone in the penis of dogs that partially surrounds the penile portion of the urethra
  • The urethral groove on the ventral surface of the bone encloses the dorsal portion of the urethra

The Skeletal System

• The skeleton can be divided into two main groups: Axial Skeleton and Appendicular Skeleton
• Axial Skeleton consists of bones in the head and trunk
• Appendicular Skeleton consists of bones in the limbs

Axial Skeleton

• Bones of the head and trunk
• Located along the central axis of the body
• Includes:
  • Skull
  • Hyoid bone
  • Spinal column (vertebrae)
  • Ribs
  • Sternum

Skull

• Made up of 37-38 bones in domestic animals
• Bones are held together by fibrous, immovable joints called sutures
• Only the mandible (lower jaw) is connected to the rest of the skull by a freely movable synovial joint
• Can be divided into three regions:
  • Bones of the cranium
  • Bones of the ear
  • Bones of the face

Skull - Bones of the Cranium

• External bones of the cranium surround the brain
• Includes:
  • Occipital bones
  • Interparietal bones
  • Parietal bones
  • Temporal bones
  • Frontal bones

Skull - Bones of the Face

• External bones of the face
• Includes:
  • Incisive bones (house the upper incisor teeth)
  • Nasal bones (form the bridge of the nose)
  • Maxillary bones (make up most of the upper jaw)
  • Lacrimal bones (form part of the eye orbit)
  • Zygomatic bones (form part of the eye orbit and zygomatic arches)
  • Mandible (forms the lower jaw and joins the temporal bone at the temporomandibular joint)

Hyoid Bone

• Looks like the letter H with its two legs bent back to form a U-shaped structure
• Located high in the neck, just above the larynx
• Supports the base of the tongue, pharynx, and larynx and helps the animal swallow

The Spinal Column

• Also known as the vertebral column
• Made up of individual irregular bones (vertebrae)
• Divided into five regions:
  • Cervical (neck)
  • Thoracic (chest)
  • Lumbar (lower back)
  • Sacral (pelvis)
  • Caudal (tail)
• Individual vertebrae are numbered within each region
• Vertebrae are separated by intervertebral discs (fibrocartilage) which act as shock absorbers

The Spinal Column - Cervical Vertebrae

• 7 vertebrae in dogs and cats
• C1 = Atlas, C2 = Axis, rest of cervical vertebrae are numbered
• Atlas has "Wings of the Atlas" (transverse processes) and holds up the head
• Axis has spinous processes that project dorsally and a peg-like "dens" that fits into the atlas to form the atlantoaxial joint

The Spinal Column - Thoracic Vertebrae

• Located dorsal to the thorax (chest)
• Animals usually have the same number of thoracic vertebrae as pairs of ribs
• Have very tall, spinous processes
• Lateral facets form joints with the ribs

The Spinal Column - Lumbar Vertebrae

• Located dorsal to the abdominal region
• Have large, bulky bodies to support the abdominal contents
• Compared to the thoracic vertebrae, which have the support of the ribs

The Spinal Column - Sacral Vertebrae

• Located dorsal to the pelvic region
• Forms a joint with the pelvis on each side called the sacroiliac joint
• Sacral vertebrae are unique in that they fuse to form a single solid structure called the sacrum

The Spinal Column - Caudal (Coccygeal) Vertebrae

• Form the bones of the tail
• Number and appearance vary greatly between and within a species and even within an individual
• In humans, these are fused to form the coccyx or "tailbone"

Ribs

• Flat bones, form lateral part of thorax
• The number of pairs of ribs usually equals the number of thoracic vertebrae
• Dorsal ends: the heads of the ribs form joints with the thoracic vertebrae
• Ventral ends: the costal cartilages either join the sternum directly or join the costal cartilage ahead of them

Sternum

• Also known as the "breastbone"
• Forms the floor of the thorax
• Made up of bones called sternebrae
• Only the first and last sternebrae are named and used as landmarks, the rest are numbered

Appendicular Skeleton

• Made up of the bones of the main appendages of the animal (i.e. the limbs)
• Divided into two parts:
  • Thoracic limb (forelimb)
  • Pelvic limb (hindlimb)

Thoracic Limb

• Includes:
  • Scapula
  • Humerus
  • Radius
  • Ulna
  • Carpal bones
  • Metacarpal bones
  • Phalanges

Scapula

• Most proximal bone of the thoracic limb
• Flat, somewhat triangular bone with a prominent, longitudinal ridge on its lateral surface
• At its distal end, it forms the socket portion of the ball-and-socket shoulder joint

Humerus

• The long bone of the upper arm (brachium)
• Proximal end: ball and socket shoulder joint
• Distal end: elbow joint with radius and ulna

Ulna

• Forms the antebrachium (forearm) with the radius
• Proximal end: forms part of the elbow joint with the distal end of the humerus
• Distal end articulates with the carpus

Radius

• The main weight-bearing bone of the antebrachium (forearm)
• Proximal end articulates with the proximal end of the ulna and also joins with the distal end of the humerus
• Shaft varies from fairly straight in cats and cattle to somewhat bowed in dogs, horses, and swine

Carpus

• Carpus = two rows of carpal bones
• Proximal row: radial carpal bone, ulnar carpal bone, accessory carpal bone
• Distal row: numbered from medial to lateral

Metacarpus

• The metacarpal bones extend distally from the distal row of carpal bones to the proximal phalanges of the digits
• Dogs and cats typically have five digits or toes making up their front paws
• Dogs have five metacarpal bones that are numbered from medial to lateral

Phalanges

• Each digit is made up of 2-3 bones called phalanges
• "Phalanges" = the individual bones that make up the digits
• Dog and cat forepaws contain bones similar to human fingers

Pelvic Limb

• Includes:
  • Pelvis
  • Femur
  • Patella
  • Fabellae
  • Tibia
  • Fibula
  • Tarsus (hock)
  • Metatarsus
  • Phalanges

Pelvis

• Develops as three separate bones on each side that eventually fuse into a solid structure
• Two halves are joined ventrally by a cartilaginous joint called the pelvic symphysis
• Pelvis joins the axial skeleton dorsally at the sacroiliac joints

Femur

• Long bone of the thigh
• Proximal end: ball portion of ball-and-socket hip joint
• Distal end: forms the stifle joint with the patella and tibia

Patella

• The patella or kneecap is the largest sesamoid bone in the body
• Forms in the distal tendon of the large quadriceps femoris muscle on the cranial aspect of the stifle joint

Tibia

• Main weight-bearing bone of the lower leg
• Proximal end: forms stifle joint with femur above
• Distal end: forms the hock with the tarsus below

Fibula

• Thin bone in dogs and cats that parallels the tibia
• Does not support any significant weight but mainly serves as a muscle attachment site

Tarsus (Hock)

• Known as the hock in four-legged animals (humans = ankle)
• Two rows of short bones (tarsal bones)
• Proximal row: named, and the distal row is numbered (from medial to lateral)

Metatarsus

• Almost the same as the metacarpal bones
• The main difference is that there are usually only four digits making up the paw on the hindleg

Phalanges

• The phalanges of the pelvic limb are almost exactly like the phalanges of the thoracic limb
• The only major difference is that there are usually only four digits making up the paw on each hind leg

The Skeletal System

• The skeleton can be divided into two main groups: the axial skeleton and the appendicular skeleton.

Axial Skeleton

• The axial skeleton consists of the bones of the head and trunk, located along the central axis of the body.
• It includes the skull, hyoid bone, spinal column, ribs, and sternum.

Skull

• The skull is made up of 37-38 bones in domestic animals.
• These bones are held together by fibrous, immovable joints called sutures.
• Only the mandible (lower jaw) is connected to the rest of the skull by a freely movable synovial joint.
• The skull can be divided into regions: bones of the cranium, bones of the ear, and bones of the face.
• The bones of the cranium include the occipital, interparietal, parietal, temporal, and frontal bones.
• The bones of the face include the incisive, nasal, maxillary, lacrimal, zygomatic, and mandible bones.

Hyoid Bone

• The hyoid bone is a U-shaped structure located high in the neck, just above the larynx.
• It supports the base of the tongue, pharynx, and larynx, and helps the animal swallow.

Spinal Column

• The spinal column, also known as the vertebral column, is made up of individual irregular bones called vertebrae.
• It is divided into five regions: cervical, thoracic, lumbar, sacral, and caudal (coccygeal).
• Each vertebra is numbered within its region.
• The spinal column is flexible due to the intervertebral discs (fibrocartilage) that separate the vertebrae.

Ribs

• The ribs are flat bones that form the lateral part of the thorax.
• The number of pairs of ribs usually equals the number of thoracic vertebrae.
• The dorsal ends of the ribs form joints with the thoracic vertebrae.
• The ventral ends of the ribs have two parts: a dorsal part made of bone, and a ventral part made of cartilage.

Sternum

• The sternum, also known as the breastbone, forms the floor of the thorax.
• It is made up of bones called sternebrae.
• The first and last sternebrae are named and used as landmarks, while the rest are numbered.

Appendicular Skeleton

• The appendicular skeleton consists of the bones of the limbs.
• It is divided into the thoracic limb and the pelvic limb.

Thoracic Limb

• The thoracic limb consists of the scapula, humerus, radius, ulna, carpal bones, metacarpal bones, and phalanges.
• The scapula is the most proximal bone of the thoracic limb.
• The humerus is the long bone of the upper arm.
• The radius and ulna are the bones of the forearm.
• The carpal bones are the bones of the wrist.
• The metacarpal bones are the bones of the hand.
• The phalanges are the bones of the digits.

Pelvic Limb

• The pelvic limb consists of the pelvis, femur, patella, fabellae, tibia, fibula, tarsus, metatarsus, and phalanges.
• The pelvis develops as three separate bones on each side that eventually fuse into a solid structure.
• The pelvis joins the axial skeleton dorsally at the sacroiliac joints.
• The femur is the long bone of the thigh.
• The patella is the largest sesamoid bone in the body.
• The tibia is the main weight-bearing bone of the lower leg.
• The fibula is a thin bone that parallels the tibia.
• The tarsus is the ankle or hock.
• The metatarsus is the foot.
• The phalanges are the bones of the toes.

Visceral Skeleton

• The visceral skeleton consists of bones that form in soft organs or viscera.
• The os penis is a bone in the penis of dogs that partially surrounds the penile portion of the urethra.

Axial Skeleton

• The axial skeleton includes the skull, hyoid bone, spinal column, ribs, and sternum.
• The hyoid bone is a U-shaped structure located high in the neck, supporting the base of the tongue, pharynx, and larynx, and helping with swallowing.
• It is composed of several individual portions united by cartilage.

Skull

• The skull is made up of 37-38 bones in domestic animals, which are held together by fibrous immovable joints called sutures.
• Only the mandible (lower jaw) is connected to the rest of the skull by a freely movable synovial joint.
• The skull can be divided into regions: bones of the cranium, bones of the ear, and bones of the face.

Bones of the Cranium

• The cranium is the part of the skull that surrounds the brain.
• External bones of the cranium include the occipital bones, interparietal bones, parietal bones, temporal bones, and frontal bones.

Bones of the Face

• External bones of the face include:
  • Incisive bones, which house the upper incisor teeth.
  • Nasal bones, which form the bridge of the nose.
  • Maxillary bones, which make up most of the upper jaw and part of the hard palate.
  • Lacrimal bones, which form part of the eye orbit and house the lacrimal duct for tear drainage.
  • Zygomatic bones, which form part of the eye orbit and join with the temporal bones to form zygomatic arches.
  • Mandible, which forms the lower jaw and is the only movable skull bone.

Spinal Column

• The spinal column, also known as the vertebral column, is made up of individual irregular bones called vertebrae.
• The spinal column is divided into five regions: cervical, thoracic, lumbar, sacral, and caudal (coccygeal).
• Each vertebra has a body, arch, and several processes, including sites for muscle attachment and leverage for movement.

Vertebrae Regions

• Cervical vertebrae are located in the neck region and have 7 vertebrae in dogs and cats.
• Thoracic vertebrae are located dorsal to the thorax (chest) and have very tall, spinous processes.
• Lumbar vertebrae are located dorsal to the abdominal region and have large, bulky bodies to support the abdominal contents.
• Sacral vertebrae are located dorsal to the pelvic region and fuse to form a single solid structure called the sacrum.
• Caudal (coccygeal) vertebrae form the bones of the tail and vary greatly in number and appearance between species and individuals.

Ribs

• Ribs are flat bones that form the lateral part of the thorax.
• The number of pairs of ribs usually equals the number of thoracic vertebrae.

Appendicular Skeleton

• The appendicular skeleton includes the bones of the limbs.
• It is divided into the pelvic limb and the thoracic limb.

Pelvic Limb

• The pelvic limb includes:
  • Pelvis
  • Femur
  • Patella
  • Fabellae
  • Tibia
  • Fibula
  • Tarsus (hock)
  • Metatarsus
  • Phalanges

Pelvis

• The pelvis develops from three separate bones on each side that eventually fuse into a solid structure.
• The pelvis joins the axial skeleton dorsally at the sacroiliac joints.
• The pelvis has three main regions: ilium, ischium, and pubis.

Pelvis Functions

• The pelvis is responsible for weight-bearing from the hindlimbs.
• It protects and supports the intestines, bladder, and internal sex organs.

Visceral Skeleton

• The visceral skeleton consists of bones that form in soft organs or viscera.
• It is a variable and unusual division of the skeleton.
• Examples include the os penis in dogs, which partially surrounds the penile portion of the urethra.