The Skeletal System

How many digits does each leg in a horse have?

-1 digit

Thoracic Limb Phalanges: Equine

-1 digit with 3 phalanges ----proximal phalanx (long pastern bone) ----middle phalanx (short pastern bone) ----distal phalanx (coffin bone) -Also have sesamoid bones

How many phalanges are in the digit of the horse?

-3 phalanges

Which metatarsal bones are present in dogs and cats?

-4 metatarsal bones (II to V)

Which bones form the tarsal joint?

-7 Individual bones ----talus (tibial tarsal bone) ----calcaneus (fibular tarsal bone) ----central tarsal bone ----fourth tarsal bone ----first, second, and third tarsal bones

What is a Diarthroses?

-A joint that moves freely

Bone Matrix: Inorganic Portion

-Accounts for about half the weight of bone -Significant amounts of bicarbonate, citrate, magnesium, potassium, and sodium ions

What does yellow bone marrow consist of primarily?

-Adipose Connective Tissue

Hinge Joint

-Allow movement in one plane (extends/flexes) -Also called a ginglymus -Elbow joint -Knee joint -Atlantooccipital joint (nodding "yes")

What are Amphiarthroses?

-Allow some degree of movement between the bones

Plane/Gliding Joints

-Allows movement in two planes: mainly flexion/extension with some abduction and adduction -Articular surfaces are nearly flat -Tarsus and Carpus

How do bones grow in diameter?

-Appositional Growth: growth by adding to the free surface of the bone -Can occur at the endosteum or periosteum ----osteoclasts resorb old bone that lines the medullary cavity ----osteoblasts produce new bone tissue -Increases the diameter of the diaphysis and medullary cavity -Remodeling primarily takes place during a bone's growth -In adults, bone undergoes constant remodeling ----injury, exercise, and other activities lead to remodeling

Costochondral Junction

-Area where costal cartilage meets bony ribs

Acetabulum

-Articular socket -Where the head of the femur sits, forming the hip joint

Radius

-Articulates with the humerus and the ulna -Styloid process articulates with the carpus

Talus

-Articulates with the tibia and fibula -Located medially and has 3 body parts --Body ----trochlea ----trochlear ridges articulate with the tibia --Head ----articulates with the central tarsal bone --Connecting Neck

Five Zones of the Epiphyseal Plate

-As cartilage grows, entire structure grows in length and then is turned into bone -Elongation stops once cartilage cannot grow further

Where is costal cartilage found?

-At the ventral ends of the ribs -Join the sternum or the costal cartilage ahead of them

What is another name for C1?

-Atlas -Wing Bone (a)

What is another name for C2?

-Axis -Tooth Bone (b)

What is the Haversian Canal?

-Blood Vessels -Lymph Vessels -Nerves

What are the main functions of endosteum?

-Bone Growth -Bone Repair -Bone Remodeling

What is the splanchnic (visceral) skeleton?

-Bone that develops in soft tissue and is unattached to the rest of the skeleton

Splanchnic (Visceral) Skeleton

-Bone that develops in soft tissue and is unattached to the rest of the skeleton -os cordis: in the heart of cattle and sheep -os penis: in the penis of dogs, cats, ferrets, beavers, raccoons, and walruses -os rosti: in the nose swine

What metacarpal bones are present in cows?

-Bones III and IV that are fused together

Which type of bones develop through endochondral bone formation?

-Bones at the base of the skull -Long bones

What is another name for the sternum?

-Breastbone

What is the primary component of the inorganic portion of the bone matrix?

-Calcium Hydroxyapatite

Types of Bone

-Cancellous -Compact

Ball-and-socket Joint

-Capable of flexion, extension, abduction, adduction, rotation, and circumduction -Hip Joint -Shoulder Joint

Short Bones

-Carpel and Tarsal bones -Small and roughly cube-shaped -Contain mainly cancellous bone, with a thin outer layer of cortical bone

Floating Rib Definition

-Cartilage does not join anything ----often end in the muscles of the thoracic wall

Intervertebral Disks Definition

-Cartilage separating bodies of adjacent vertebrae

What is the pubic/pelvic symphysis?

-Cartilaginous joint between the halves of the pelvis

Ischium

-Caudal most pelvic bone -Forms caudal portion of the pelvic floor -Ischial Tuberosity: caudal projection

What is another name for a Haversian system?

-Central Canal

Which type of bones develop through intramembranous bone formation?

-Certain flat bones of the skull -Some of the irregular bones

Vertebral Regions

-Cervical (Neck) ----C1 (atlas) ----C2 (axis) -Thoracic -Lumbar -Sacral -Coccygeal

Nutrient Foramina Definition

-Channels in may large bones ----contains large blood vessels, lymph vessels, and nerves

Volkmann Canal Definition

-Channels through bone matrix that contains blood vessels ----joins with blood vessels in the Haversian system

What is another name for the distal phalanx of the horse?

-Coffin bone

What are the components of the organic portion of the bone matrix?

-Collagen Fibers (type I) -Proteoglycans -Glycoproteins (ex: osteonectin and osteocalcin)

Which type of bone is composed of Haversian systems?

-Compact Bones

Haversian System (Osteons) Features

-Concentric layers of ossified bone matrix arranged around a central canal

Bony Features of Articular Surfaces

-Condyle: large, round articular surface -Head: spherical articular surface on the proximal end of a long bone ----joins with the shaft of the bone at the neck region -Facet: flat articular surface

Pelvis

-Connects hindlimb to the body -Two hip bones (ossa coxarum) -Joins together at pubic/pelvic symphysis ----cartilaginous joint between the halves of the pelvis -Meet at the Acetabulum ----ilium ----ischium ----pubis

Vertebrae Features

-Consists of a body, an arch, and processes -Contains several processes: ----spinous process ----transverse processes ----articular processes

Condylar Joint

-Consists of a convex surface (condyles) that sits in a corresponding concave surface -Allows flexion/extension and side-to-side movement -Temporomandibular joint (TMJ)

What is another name for compact bones?

-Cortical Bone

VERTEBRAL FORMULA (add more)

-DOGS (C7 T13 L7 S3 Cd20-23)

Endosteum Bone Structure Features

-Delicate membrane that lines the hollow interior surfaces of bones

Compact Bone Features

-Dense and Heavy

Fossa Definition

-Depressed area on the surface of a bone

Where is the primary growth center in long bones that develop during endochondral bone formation?

-Develop in the diaphysis -Cartilage is removed as bone is created

Where is the secondary growth center in long bones that develop during endochondral bone formation?

-Develop in the epiphysis

How does bones develop during endochondral bone formation?

-Develops by replacing hyaline cartilage ----hyaline cartilage serves as a template and is completely replaced by new bone -Takes longer than intramembranous ossification

What is another name for digit I in the dog and cat?

-Dewclaw

Synovial Joints

-Diarthroses -Joint Capsule: surrounds and protects the joint ----outer layer consists of fibrous tissue -Synovial membrane lines the joint cavity and secretes synovial fluid ----lubricates the joint ----provides nutrition for the hyaline articular cartilage

Thoracic Limb Phalanges: Canine and Feline

-Digit I (dewclaw) ----one proximal phalanx ----one distal phalanx -Digit II to V ----proximal phalanx ----middle phalanx ----distal phalanx -------ungual process

What are the two types of bone formation?

-Endochondral -Intramembranous

What are the two main parts of the medullary cavity?

-Endosteum -Periosteum

Metacarpal Bones

-Extended distally from distal carpal bones to proximal phalanges -Dogs and Cats (5 Digits) ----numbered medial to lateral ----metacarpal I: dewclaw

Bones of the Face

-External ----Incisive bones (2) ----Lacrimal bones (2) ----Mandible (1 or 2) ----Maxillary bones (2) ----Nasal bones (2) ----Zygomatic bones (2) -Internal ----vomer bone (1) ----turbinates (4) ----pterygoid bones (2) ----palatine bones (2)

Bones of the Cranium

-External Bones ----frontal bones (2) ----interparietal bones (2) ----occipital bones (1) ----parietal bones (2) ----temporal bones (2) -Internal Bones ----ethmoid bone (1) ----sphenoid bone (1)

Which long bone forms the thigh?

-Femur

Which bones form the hip joint?

-Femur ----proximal end

Classification of Joints

-Fibrous Joints: immovable -Cartilaginous Joints: slightly movable -Synovial Joints: freely movable

What is the function of bone marrow?

-Fills the spaces within bones

Scapula

-Flat, triangular bone -Spine of the scapula: longitudinal ridge on lateral surface -Glenoid Cavity: shallow, concave articular surface

Synovial Joint Movements

-Flexion -Extension -Adduction -Abduction -Rotation -Circumduction

Foramen Definition

-Foramina is pleural -Hole in a bone; may contain blood vessels, nerves

What is the function of red bone marrow?

-Forms all blood cells

Pubis

-Forms cranial portion of the pelvic floor

What do the vertebral arches line up to form?

-Forms the spinal canal

Types of Synovial Joints

-Gliding Joint -Pivot Joint -Condylar Joint -Hinge Joint -Ball-and-socket Joint

Bone Cells: Osteoblast Features

-Helps control Ca and P levels in the body -Secrete an organic matrix rich in collagen protein -Immature cells formed from osteogenic stem cells -Help regulate bone resorption

What is the long bone of the brachium?

-Humerus

What bones form the elbow joint?

-Humerus -Radius -Ulna

What type of cartilage is found on the articular surface of synovial joints?

-Hyaline cartilage

What is the most cranial-most and largest pelvic bone?

-Ilium (the wing part)

Where is the sacroiliac joint?

-Ilium forms this joint with the sacrum

Where are Osteoclast found?

-In areas of: ----active bone growth ----repair or remodeling ----removal of calluses formed during fracture healing

What is another name for the carpus in hoofed animals?

-In hoofed animals, the carpus is the "knee"

Where is cancellous bone typically found?

-In spaces between the spicules contain bone marrow

How do bones elongate?

-Includes a layer of hyaline cartilage where ossification can continue to occur in immature bones -Diaphyseal Side (closer to the diaphysis) ----cartilage calcified and dies, and then is replaced by bone ----zones of hypertrophy and maturation, calcification and ossification -Epiphyseal Side (closer to the epiphysis) ----hyaline cartilage cells actively divide and produce matrix ---reserve and proliferative zones

Bones of the Ear

-Incus (2) -Malleus (2) -Stapes (2)

Where are osteocytes found?

-Inside the mature bones -Inhabit spaces called lacunae

Bone Matrix

-Intercellular substance that forms most of the bone mass -Has an inorganic portion -Has an organic portion

Meniscus (menisci)

-Intraarticular fibrocartilaginous discs -Stifle joint has two crescent-shaped menisci -Temporomandibular joint between the mandible and the skull -Help increase the range of movement of the joint -Act as "shock absorbers"

What is the caudal-most pelvic bone?

-Ischium

Which bone forms the caudal portion of the pelvic floor?

-Ischium

What is the Ungual Process?

-It is apart of the canine and feline thoracic limb phalanges -It surrounds the claw on the distal phalanx

What type of tissue is bone?

-It is the hardest and most rigid connective tissue -The second hardest substance in the body (1st is Enamel)

Obturator Foramen

-Large hole on either side of the pubic symphysis -Reduces the weight of the pelvic girdle -Provides extra surface area for the attachment of muscles and ligaments

Patella

-Large sesamoid bone -Formed in the tendon of insertion of the quadriceps femoris muscle ----main extensor muscle of the stifle -Protects the tendon

Ilium

-Largest of the hip bones -Projects in dorsocarnial direction -Wing: broad cranial expansion -Forms the sacroiliac joint with the sacrum

Calcaneus

-Largest of the tarsal bones -Articulates with the talus and fourth tarsal bone -Small articulation with the central tarsal bone -Tuber Calcanei ----proximal part of the bone ----attachment site for the common calcaneal tendon -Sustentaculum Tali ----bony process on the medial side

Is the fibula the medial or lateral lower hindlimb bone?

-Lateral

Fourth Tarsal Bone

-Lateral and central -Articulates on the medial surface with the central and third tarsal bones -Articulates proximally with the calcaneus -Articulates distally with the fourth and fifth metatarsal bones

Cancellous Bone Features

-Light and spongy -Tiny spicules of bone that appear randomly arranged

Femur

-Long bone that forms the thigh -Proximal end forms part of the hip joint -Femoral head faces medially and articulates with the acetabulum of the pelvis ----head joins the shaft at the neck ----round ligament attaches the acetabular fossa and holds the femoral head in place -Greater Trochanter: projection lateral to the femoral head ----site of muscle attachment -Lesser Trochanter: smaller projection on the medial side ----site of muscle attachment -Medial and lateral condyles ----project causally on the distal femur ----articulates with the tibia at the stifle joint -Trochlea Groove: articular groove between the 2 condyles that contain the patella

What is another name for the proximal phalanx of the horse?

-Long pastern bone

What is the purpose of the synovial joints?

-Lubricates the joint -Provide nutrition for the hyaline articular cartilage

Tibia

-Main weight-bearing bone of the lower hindlimb -Larger, more medial bone -Forms the stifle joint with the femur -Forms tarsus (hock) with the talus -Medial malleolus ----distal protrusion that can be palpated on the medial aspect of the hock -Tibial Tuberosity -Tibial crest ----prominence on the dorsal surface ----attachment site for quadriceps femoris muscle

Bone Cells: Osteocyte Features

-Mature cells formed from osteoblasts -Star-shaped cells with projections

Is the tibia the medial or lateral lower hindlimb bone?

-Medial

Central Tarsal Bone

-Medial -articulates with all of the other tarsal bone -acts as a buttress support for the joint

Which part of the bone contains the epiphyseal plate?

-Metaphysis

Osteocyte Functions

-Molecular Synthesis -Modification -Distant Signal Transmission -Major Regulator of Bone Mass -Endocrine Regulator in Phosphate Metabolism -Destruction can lead to Osteoporosis

Xiphoid Process Definition

-Most caudal sternebra (last)

Manubrium Sterni Definition

-Most cranial sternebra (first)

Circumduction

-Movement of an extremity so that the distal end moves in a circle

Sesamoid Bones

-Navicular bone of horses -Patella (kneecap) -Fabellae -Round or oval bones that develop in tendons -Protect tendons from stress and wear

Is periosteum found on a articular surface?

-No, not present

How are the metatarsal bones numbered?

-Numbered I to V from medial to lateral

How are the pelvic limb phalanges and digits numbered?

-Numbered I to V from medial to lateral -Except dogs and cats usually have only 4 digits (II to V)

Ulna

-Olecranon Process ----point of the elbow ----site for tendon attachment of triceps brachii muscle -Trochlear Notch: concave articular surface (look for the "U", it is where the humerus sits) -Anconeal and Coronoid Processes

Where are osteoblasts found?

-On the surface of new bones

Metacarpal Bones in Horses

-One large metacarpal bone (cannon bone) ----metacarpal III -Two smaller vestigial metacarpal bones ----splint bones ----non weight-bearing ----metacarpal II and IV

Metatarsal Bones: Horses

-One large metatarsal bone (cannon bone) -Two small metatarsal bones (splint bones)

Pivot Joint

-Only movement is rotation -Atlantoaxial joint (shaking your head "no")

Flexion and Extension

-Opposite Movements -Increases or decreases the angle between two bones

Adduction and Abduction

-Opposite movements -Move an extremity toward or away medial plane

Which bone cell type produces bone?

-Osteoblast

What cell type is found in the inner layer of the periosteum?

-Osteoblasts

What cell type produces and secretes the organic portion of the bone matrix?

-Osteoblasts

Types of Bone Cells

-Osteoblasts -Osteocytes -Osteoclasts

Which large, multinucleated bone cell type is primarily responsible for remodeling/removing bone?

-Osteoclasts

Which bone cell type maintains bone matrix?

-Osteocytes

Periosteum Definition

-Outer layer is composed of fibrous tissue -Inner layer contains osteoblasts -Membrane that covers the outer surfaces of bones -Contains blood and lymphatic vessels and nerves -Site of attachment to tendons and ligaments -Anchored and attached to underlying bone by fibrous structures called Sharpey's fiber

Pelvic Limbs

-Pelvis -Ilium -Ischium -Femur -Patella -Tibia (crus) -Fibula (crus) -Tarsal Bones (tarsus) -Metatarsal Bones -Phalanges

Bone Features: Processes

-Projections off of a bone surface -Name depends on location: ----the spinous process of a vertebra ----trochanter on the femur ----tuberosity on the ischium ----spine on the scapula ----wing on the atlas

What is the main function of the periosteum?

-Provide nutrition for compact bone

Carpus

-Proximal Row (3 Bones) --intermedioradial carpel bone ----most medial ----articular proximally with radius --ulnar carpel bone ----articulates proximally with ulna --accessory carpel bone ----most medial lateral and projects caudally -Distal Row (4 Bones) --numbered medial to lateral --C1 to CIV

What type of cartilage covers the epiphysis of long bone?

-Proximal and Distal ----Covered with a layer of articular cartilage (hyaline cartilage) that allows bones to slide past one another more easily

Which bone forms the cranial portion of the pelvic floor?

-Pubis

What is the main weight-bearing bone of the antebrachium?

-Radius

What are the types of bone marrow?

-Red Bone Marrow -Yellow Bone Marrow

How does bone develop during intramembranous bone formation?

-Replacement of sheet-like connective tissue membranes with bony tissue

What flat bones form the lateral walls of the thorax?

-Ribs

Epiphysis Bone Structure Features

-Round end of a long bone ----shape facilitates contact and motion with joints -Interior filled with spongy bone -Some are sites of blood cell production in adults

Thoracic Limbs

-Scapula -Humerus -Radius (antibrachium (forearm)) -Ulna (antibrachium (forearm)) -Carpel bones (carpus) -Metacarpal bones -Phalanges

What bones form the shoulder joint?

-Scapula -Humerus (proximal)

What separates the diaphysis from the epiphysis?

-Separated from epiphysis by the epiphyseal line/plate in the metaphysis

Metaphysis Bone Structure Features

-Separates epiphysis and diaphysis -Contains the epiphyseal plate (growth plate) ----a layer of hyaline cartilage in growing bone -Osseous tissue replaces cartilage as the growth phase is completed ----epiphyseal plate becomes an epiphyseal line

Diaphysis Bone Structure Features

-Shaft of a long bone -Long and cylindrical

Where are compact bones typically found?

-Shafts (outer layer) of long bones -Outside layer of all bones

What is another name for the middle phalanx of the horse?

-Short pastern bone

Bones of the Axial Skeleton

-Skull -Hyoid Bone -Spinal Column -Ribs -Sternum

Flat Bones

-Skull -Ribs -Scapula -Thin and usually slightly curved -Typically contain a thin layer of cancellous bone surrounded by cortical bone -Most are located in the axial skeleton -Protect underlying structures

Hyoid Bone

-Sometimes included with the cranial bones -Also called the hyoid apparatus -Composed of serval portions of bone united by cartilage

What are intracapsular ligaments?

-Stabilizing ligaments attached to the articulating bones within the joint -Cruciate ligaments within the stifle joint

Which bone forms the floor of the thoarx?

-Sternum

What bones form the carpel joint?

-Styloid -Intermedioradial Carpel Bone -Ulnar Carpel Bone

Functions of Bone

-Support and Movement -Protection -Mineral Homeostasis -Triglyceride Storage -Production of Blood Cells

What are most of the skull bone joints called?

-Sutures

Fibrous Joints

-Synarthroses -United by dense fibrous connective tissue -Examples: sutures of the skull

What type of joint connects the mandible to the rest of the skull?

-Synovial Joint

Where are menisci found?

-Temporomandibular joint between the mandible and the skull

What is another name for the Scapulohumeral Joint?

-The Shoulder Joint

What is the antebrachium?

-The forearm

What is the point of the elbow?

-The olecranon process

Which vertebrae do the dorsal heads of the ribs articulate with?

-The thoracic vertebrae

What is the diaphysis composed of?

-Thick layer of compact bone surrounding the medullary cavity

What are collateral ligaments?

-Thickened ligaments in fibers of the joint capsule -Provide additional stabilization -Most commonly found on either side of the joint

Fibula

-Thin long bone lateral to the tibia -Ends in a bony point called the lateral malleolus -Not weight-bearing -Serves as a muscle attachment site

Bones of the Appendicular Skeleton

-Thoracic Limbs -Pelvic Limbs

What is the main weight-bearing bone of the lower hindlimb?

-Tibia

What is the main function of the bone matrix?

-To provide mechanical support for the bones

Humerus

-Tubercles: processes where shoulder muscles attach -Condyles: articular surfaces ----trochlea: articulates with the ulna ----capitulum: articulates with the radius -Olecranon Fossa: indentation above the condyle -Epicondyles: non-articular

Rotation

-Twist movement of a part on its own axis

Thoracic Limb Phalanges: Bovine

-Two digits that support the weight -Each digit has a proximal, middle, and distal phalanx -Proximal and distal sesamoid bones

Fabellae

-Two small sesamoid bones behind stifle in gastrocnemius muscle tendons of dogs and cats -Articulate with femoral condyles -Not present in cattle or horses

What are the splint bones in the horses?

-Two smaller vestigial metacarpal bones

What are Synarthroses?

-Type of joint that permits little or no movement

Long Bones

-Typically longer than they are wide -Humerus -Radius -Tibia -Ulna -Femur -Fibula

Which bone contains the olecranon process?

-Ulna

How are cartilaginous joints united?

-United by cartilage -Ex: mandibular symphysis (synarthroses) -Ex: pubic symphysis (amphiarthroses)

Cartilaginous Joints

-United by cartilage -Synarthroses ----mandibular symphysis ----pubic symphysis -Amphiarthroses ----intervertebral disk (allows flexibility of the spinal column

How are fibrous joints called?

-United by dense fibrous connective tissue -Ex: sutures of the skull

What is the brachium?

-Upper arm

Number of Bones in the Skull

-Usually consists of 37 or 38 separate bones

Irregular Bones

-Vertebrae -Pelvis -Bones that do not fit in other categories because they have a range of different characteristics -Cancellous bone, with an outer layer of cortical bone

What is the most common type of bone marrow in adults

-Yellow Bone Marrow -Can revert to red bone marrow if needed

Medullary Cavity Bone Structure Features

-Yellow marrow cavity in adults -Red marrow cavity in infants

Where is red bone marrow found in young animals and in adults?

-Young Animals: majority of the young -In Adults, ----ribs ----sternum ----vertebrae ----ends of long bones