The Skeletal System Flashcards
Osteblasts
Cells that form bone, secrete the matrix
The matrix
Intercellular substance
Ossification
The matrix is infiltrated with calcium and phosphate in the form of hydroxyapatite crystals
Hydroxyapatite crystals
Give bone its characteristic hardness
Lacunae
The ossified matrix
Canaliculi
Cellular processes in tiny channels through the bone, osteocytes obtain food and communicate w each other
Functions of bones
Support, protection, leverage, and storage
Two hormones that act as “cashiers” at the calcium bank
Calcitonin (prevents hypercalcemia) and parathyroid hormone (prevents hypocalcemia)
Calciotropic
The hormones are involved in the regulation of calcium levels in the body
Hematopoisesis
Blood cell formation
Two main types of bone
Cancellous bone and compact bone
Cancellous bone
Light and spongy, consists of tiny spicules of bone that appear randomly arranged w lots of spaces btwn them
Compact bone
Heavy and dense, makes up shafts of long bones and the outside layer of all bones. Composed of tiny, tightly compacted cylinders of bone called Haversian systems
Haversian canal
Contains blood vessels, lymph vessels, and nerves that supply the osteocytes
Periosteum
A membrane that covers the outer surfaces of bones
Endosteum
A membrane that lines the hollow interior surfaces of bones
3 type of cells that make up bone:
Osteoblasts, osteocytes, and osteoclasts
Osteocytes
Created once the osteoblast becomes trapped in the ossified matrix
Osteoclasts
Instead of forming bone, they eat it away, also allow the body to withdraw calcium from the bones when necessary
Volkmann’s canals
Tiny channels in the bone matrix, blood vessels here join w the blood vessels in the Haversian canals to bring nutrition to the osteocytes in the Haversian systems
Nutrient foramina
Large blood vessels, along with lymph vessels and nerves,
also enter many large bones, especially long bones, through large channels called nutrient foramina
2 ways bone is formed:
Grows into and replaces a cartilage model (endochondral or cartilage bone formation), or it develops from fibrous tissue membranes (intramembranous or membrane bone formation)
Endochondral bone formation
The body creates a cartilage “template” that is subsequently replaced by bone
Femur
Thigh bone
Diaphysis
Shaft of the bone, main part of long bone, consists of compact bone
Secondary growth centers
Additional growth centers, develop in the ends of the bone
Epiphyses
Ends of the bone
Areas of a long bone that remains as cartilage when an animal is born:
Epiphyseal plates / growth plates
Intramembranous bone formation
Bone forms in the fibrous tissue membranes that cover the brain in the developing fetus. Occurs only in certain skull bones and creates flat bones of the cranium
Callus
Healing tissue formed by osteoblasts when a bone is broken, gradually bridges the fracture gap
Long bones
Longer than they are wide, most bones of the limbs, has proximal & distal epiphysis
Epiphyseal fractures
Fractures through epiphyseal plates, common in young animals
Short bones
Shaped like small cubes or marshmallows, consists of a core of spongy bone covered by a thin layer of compact bone
Distal & proximal epiphysis
Consist primarily of light, cancellous bone covered by a thin layer of compact bone, located on long bone
Flat bones
Relatively thin and flat, structure is like a cancellous bone sandwich that consists of two thin plates of compact bone separated by a layer of cancellous bone
Irregular bone
Miscellaneous category, do not fit into the long, short, or flat categories. Either have characteristics of more than one of the other categories, or they have a truly irregular shape
Vertebrae
Bones of the spine, irregular bones
Sesamoid bones
Present in some tendons, where they change direction markedly over the surfaces of joints, irregular bones, resemble sesame seeds
Patella
Kneecap, largest sesamoid bone in the animal body
Bone marrow
Fills the spaces within bones
2 types of bone marrow:
Red and yellow bone marrow
Red bone marrow
Hematopoietic tissue, forms blood cells, makes up the majority of the bone marrow if young animals but represents only a small portion in older animals, older animals located at ends of some long bones and the interiors of the pelvic bones and sternum
Yellow bone marrow
Consists primarily of adipose connective tissue, most common type of marrow in adult animals, does not produce blood cells but it can revert to red bone marrow if the body needs to produce larger than normal number of blood cells
Articular surfaces
Joint surfaces: smooth areas of compact bone where bone come in contact w each other to form joints
Articular cartilage
Smooth thin layer of hyaline cartilage, covers articular surfaces
Condyle
Usually a large, round articular surface, somewhat cylindrical shape, major condyles are located at the distal end of the humerus and femur and on the occipital bone of the skull
Head
Somewhat spherical articular surface on the proximal end of a long bone, found on the proximal end of the humerus, femur, and ribs
Neck
The head of a bone is united with the main shaft portion of the bone by an often narrowed region called the neck
Facet
Flat articular surface, found on many bones, such as carpal and tarsal bones, vertebrae, and long bones like radius and ulna
Process
Term that includes all the lumps, bumps, and other projections on a bone
Foramen
A hole in a bone, usually something important, such as nerve or blood vessel, passes through, but there are exceptions
Fossa
A depressed or sunken area on the surface of a bone, usually occupied by muscles or tendons
Axial skeleton
Referred as this because the bones of the head and the trunk are located along the central axis of the body
Appendicular skeleton
Consist of bones of the limbs, which are appendages of the trunk
Visceral skeleton
These bones are formed in the viscera, or soft organs
Skull
Most complex part of the skeleton, in most domestic animals it consists of 37 or 38 separate bones
Sutures
Jagged, immovable, fibrous joints, which unite majority of skull bones
Synovial joint
Connects the mandible to the rest of the skull
Cranium
Portion of the skull that surrounds the brain, has 11 bones
Occipital bone
A single bone that forms that caudoventral portion or base of the skull, where the spinal cord exists the skull and it is the skull bone that articulates w the first cervical vertebra
Foramen magnum
A large hole in the center of the occipital bone: this is where the spinal cord exits the skull
Occipital condyles
Located on either side of the foramen magnum, articular surfaces that join with the first cervical vertebra to form the atlantooccipital joint
Atlas
First cervical vertebra
Atlantooccipital joint
Joint that connects the head w the neck
Interpartietal bones
2 small bones located on the dorsal midline btwn the occipital bone & the parietal bones, usually clearly visible in young animals, in older animals, they may fuse together into one bone, or they may fuse to the parietal bones and become indistinguishable
Parietal bones
The two form the dorsolateral walls of the cranium
Temporal bones
Located below or ventral to the parietal bones, they from lateral walls of the cranium, they contain the middle and inner ear structures, and they are the skull bones that form the temporomandibular joints with the mandible
External acoustic meatus
The bony canal that leads into the middle and inner ear cavities, the only ear structure that is visible from the outside
Frontal bones
Form the forehead region of the skull
The frontal sinus
A large paranasal sinus, contained within the frontal bone
The two hidden bones of the cranium:
The sphenoid bone and the more rostral ethmoid bone
Sphenoid bone
Forms the ventral part of the cranium and contains a depression
Pituitary fossa
The depression in the sphenoid bone, houses the pituitary gland
Sphenoidal sinus
A paranasal sinus present in the sphenoid bone in most animals
Ethmoid bone
A single bone located rostral to the sphenoid bone
Cribriform plate
Present in the ethmoid bone, through which the many branches of the olfactory nerve pass from the upper portion of the nasal cavity to the olfactory bulbs of the brain
Ethmoidal sinus
Small paranasal sinus present in the ethmoid bone of horses and humans
Ossicles; The 3 tiny bones in the middle ear
Malleus (hammer), incus (anvil), and stapes (stirrup)
Tympanic membrane
Eardrum
Function of the ossicles
To transmit vibrations from the tympanic membrane across the muddle ear cavity to the cochlea
Cochlea
Inner ear structure, receptor cells for hearing convert the vibrations to nerve impulses that are interpreted by the brain as sound
Incisive bones
2 bones, sometimes called the premaxillary bones, are the most rostral skull bones
Nasal bones
2 bones forming the bridge of the nose, which is the dorsal part of the nasal cavity
Dolichocephalic
Long-faced dog breeds
Maxillary bones
Two bones, make up most of the upper jaw, house all the upper teeth and the maxillary sinuses
Hard palate
Formed by the maxillary bones, the bony separation btwn the mouth and the nasal cavity or the roof of the mouth
Lacrimal bones
2 small bones that form part of the medial portion of the orbit of the eye
Lacrimal sac
Part of the tear drainage system of the eye, located in the lacrimal bones
Zygomatic bones
Also known as the malar bones, two bones forming a portion of the orbit of the eye and join w a process from the temporal bones to form the zygomatic arches on either side of the skull
Zygomatic arches
Easily palpable, bony landmarks below and behind the eyes that form the widest part of the skull in dogs and cats
Mandible
Lower jaw, houses all the lower teeth and is the only movable skull bone
Mandibular symphysis
Cartilaginous joint, unites the separate bones on either side of the mandible at their rostral ends
Shaft of the mandible
The horizontal portion that houses all the teeth
Ramus of the mandilbe
Vertical portion of the mandible, at the caudal end of the shaft of the mandible
The internal bones of the face:
Palatine bones, the pterygoid bones, the vomer bone, and the turbinates
Palatine bones
Make up the caudal portion of the hard palate, which separates the mouth from the nasal cavity
Pterygoid bones
Two small bones that support part of the lateral walls of the pharynx
Vomer bone
Located on the midline of the skull and forms part of the nasal septum
Nasal septum
The central “wall” btwn the left and right nasal passages
Turbinates
Also called the nasal conchae, are 4 thin, scroll-like bones that fill most of the space in the nasal cavity
Hyoid bone
Also called the hyoid apparatus, looks somewhat like the letter H w its 2 legs bent back to form a U-shaped structure, located high in the neck, just above the larynx, btwn the caudal ends of the mandible
Spinal column
Also called the vertebral column, is made up of a series of individual irregular bones called vertebrae that extend from the skull to the tip of the tail
The spinal column is divided into 5 regions:
Cervical, thoracic, lumbar, sacral, and coccygeal
Intervertebral discs
Made of fibrocartilage, acts as shock absorbers, separates adjacent vertebrae
Spinal canal
Long, flexible tunnel, houses and protects spinal cord
Spinous process
Single, dorsal projection process, act as sites for muscle attachment and provide leverage to move the spine and trunk
Transverse processes
Two laterally projected processes, act as sites for muscle attachment and provide leverage to move the spine and trunk
Articular processes
Located on the cranial and caudal ends of the vertebral arches and help form the joints btwn adjacent vertebrae
Cervical vertebrae
Located in neck region, nearly all mammals have
Atlas
First cervical vertebrae, C1, has 2 wing like transverse processes called wings of the atlas
Axis
Second cervical vertebrae, C2, has large bladelike spinous process that projects up dorsally and the peg like dens that fits into the caudal end of atlas to help form the atlantoaxial joint
Thoracic vertebrae
Located dorsal to the thorax, the # of thoracic vertebrae is the same as the number of pairs of ribs the animal has
Lumbar vertebrae
Dorsal to the abdominal region, most massive looking bones of the spinal column
Sacral vertebrae
Fuse to form a single, sold structure called the sacrum
Sacrum
Located dorsal to the pelvic region and forms a joint w the pelvis on each side in what is called the sacroiliac joint
Coccygeal vertebrae
The bones of the tail
Coccyx
Tailbone
Costal cartilage
Cartilaginous part of the rib
Costochondral junction
Bony part of rib
Sternal ribs
The ribs whose cartilages join the sternum and make up the cranial part of the thorax
Asternal ribs
Ribs that join the adjacent costal cartilage and make up the caudal part of the thorax
Floating ribs
Unattached ribs, may end in the muscles of the thoracic walls
Sternum
Breastbone, forms the floor of the thorax
Sternebrae
Series of rodlike bones that make up the sternum
Manubrium
The first, most cranial sternebra
Xiphoid
The last, most caudal sternebra
Appendicular skeleton
Made up of the bones of the main appendages of the animal body
Thoracic limb
Front leg
Pelvic limb
Hind leg
Glenoid cavity
The socket portion of the ball-and-socket shoulder joint, connected w the main body of the scapula by a narrowed area known as the neck
Humerus
Long bone of upper arm
Brachium
Upper arm
Antebrachium
Forearm
2 bones that form the forearm:
Ulna and radius
Ulna
Forms a major portion of the elbow joint w the distal end of the humerus
Olecranon process
Forms the point of the elbow, where the tendon of the triceps brachii muscle attaches
Trochlear notch
A half-moon shaped, concave articular surface that wraps around art of the humeral condyle to help make the elbow joint a tight, secure joint
Anconeal process
A beak-shaped process, located at the proximal end of the trochlear notch
Radius
The main weight-bearing bone of the antebrachium
Styloid process
Pointed process located at the distal end of radius
Carpus
Consists of two rows of carpal bones, in humans it’s wrist, in horses knee
Metacarpal bones
Extend distally from the distal row of carpal bones to the proximal phalanges of the digits, in hums bones of wrist to first knuckle, horses have only one large, dogs/cats have 5
Phalanges
Individual bones that make up the digits
Ungual process
Each distal phalanx contains one, surrounds the claw
Pelvic sumphysis
Cartilaginous joint joining the two halves of the pelvis ventrally
Ilium
The cranial-most bone of the pelvis, hips
Ischium
The caudal-most pelvic bone, you sit on it
Pubis
The smallest of the 3 pelvic bones, located medially and forms the cranial portion of the pelvic floor, and the ischium forms the caudal part
Acetabulum
A deep socket that tightly encloses the head of the femur to form the relatively stable hip joint
Obturator foramina
2 large holes located on either side of the pelvic symphysis, lightens the pelvis
Femur
The long bone of the thigh
Stifle joint
Equivalent to our knee, the shaft of the femur is fairly straight and extends down to the distal end to form this
Patella
Kneecap, largest sesamoid bone, helps protect tendon
Fabellae
2 small sesamoid bones located in the proximal gastrocnemius or calf muscle tendons just above and behind the femoral condyles of dogs and cats
Tibia
The main weight-bearing bone of the lower leg
Tibial crest
Ridge on tibia distal from tibial tuberosity
Fibula
A thin but complete bone in dogs and cats that parallels the tibia and consists of a proximal extremity, a shaft, and a distal extremity
Tarsus
Our ankle, in 4-legged animals commonly called hock, consists of 2 rows of short bones known as tarsal bones
Calcaneal tuberosity of the fibular tarsal bone
Projects upward and backwards to form the point of the hock
Metatarsal bones
Almost exactly the same as metacarpal bones, bones of our feet
Visceral skeleton
Consists of bones that fomr in soft organs or viscera
Os cordis
A bone in the heart of cattle and sheep that helps support valves of the heart
Os penis
A bone in the penis of dogs, beavers, racoons, and walruses that partially surrounds the penile portion of the urethra
Os rostri
A bone in the nose of swine that strengthens the snout for rooting behavior of pigs
Arthro-
Refers to joints
3 general classifications of joint in the animal body:
Immovable fibrous joints, the slightly movable cartilaginous joints, and the freely movable synovial joints
Anatomic term for fibrous joints:
Synarthroses
Fibrous joints
Are immovable in that the nones are firmly united by fibrous tissue
Cartilaginous joints
Termed amphiarthroses, capable of only a slight rocking movement
Synovial joints
Termed diarthroses, freely movable joints, contain a joint cavity, a joint capsule, and ligaments
Diarthroses
Anatomic term for synovial joints
Another term for joint cavity
Joint space
Synovial membrane
Thin barrier than lines the inside of some joints
Synovial fluid
Lubricates the joint surfaces, produced by the synovial membrane, typically transparent and a thicker viscosity
Ligaments
Bands of fibrous connective tissue that are present in and around many synovial joints
Meniscus
Shallow, concave, half-moon shaped fibrocartilage structures
Stifle joint
Equivalent to our knee
Patellar ligament
Provides support on the front of the stifle joint
Quadriceps femoris tendon
Patella and kneecap are embedded into this
Collateral
Means “on both sides”
Flexion
Decreases the angle between two bones, opposite of extension
Extension
Opposite of flexion, increases the angle between two bones
Adduction
The movement of an extremity toward the median plane, opposite of abduction
Abduction
Opposite of adduction, movement away from the median plane
Rotation
Twisting movement of a part on its own axis
Circumduction
The movement of an extremity so that the distal end moves in a circle
Types of Synovial Joints
Hinge joints, gliding joints, pivot joints, and ball-and-socket joints
Hinge joints
Also called ginglymus joints, one joint surface swivels around another, example is elbow joint
Gliding joints
Also known as arthrodial joints, the joint surfaces of a gliding joint are relatively flat and the movement btwn them is a rocking motion of one bone on the other, example is carpus or wrist
Pivot joints
Also known as trochoid joints, one bone pivots or rotates on another, the only movement possible is rotation. Only one true pivot joint found in animals is the joint btwn the first and second cervical vertebrae-the atlantoaxial joint
Ball-and-socket joints
Also called spheroidal joints, allow the most extensive movements of all the joint types and allow the synovial joint movements. Permits flexion, extension, abduction, adduction, rotation, and circumduction. Hip and shoulder joints are examples
