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