Skeletal System PDF

G en er al Ve te rin ar y Macr os copi c A na tomy : Os te olog y |4  OSTEOLOGY (G. Osteon, bone + logos, study) - is the study of bones.  BONE (osseous tissue) - the hard, semi-rigid, calcified connective tissue forming the skeleton.  SKELETON- the framework of hard structures which...

G en er al Ve te rin ar y Macr os copi c A na tomy : Os te olog y |4  OSTEOLOGY (G. Osteon, bone + logos, study) - is the study of bones.  BONE (osseous tissue) - the hard, semi-rigid, calcified connective tissue forming the skeleton.  SKELETON- the framework of hard structures which supports and protects the soft tissues of animals. Functions of the Skeleton: 1. Support- it acts as an internal ‘scaffold’ upon which the body is built; for tissue and attachment for skeletal muscles. 2. Locomotion- bones used as lever for skeletal muscles, e.g. the bones, to bring about movement. Joints allow movement. 3. Protection- it protects the underlying soft parts of the body, e.g. the brain is encased in the protective bony cranium of the skull, the spinal cord protected by the spinal cord, and the respiratory organs by the rib cage. 4. Storage- it acts as a store for the essential minerals calcium and phosphorus. 5. Hematopoiesis (blood cell formation)- hematopoietic tissue forming the bone marrow manufactures the blood cells. DIVISION Total Average Number 6. Storage of fats – energy reserve in the yellow marrow. AXIAL Skull & hyoid bone 50 The skeleton maybe divided primarily into three parts: Vertebral column 50 1. AXIAL SKELETON skull, hyoid bone, vertebral column, ribs Ribs & sternum 34 and sternum. APPENDICULAR 2. APPENDICULAR SKELETON pectoral and pelvic limbs. Pectoral 90 3. HETEROTOPIC (Splanchnic/visceral) bone that develops in Pelvic 96 the substance of some of the viscera or soft organs (os penis). HETEROTOPIC Os penis 1  STRUCTURE AND FUNCTIONS OF A BONE TOTAL 321  Classification of Bones o Bones are classified by anatomists according to shape: Characteristics Functions LONG BONE Elongated cylindrical form with enlarged Act as columns and levers (possessing great extremities; have a shaft containing a tensile strength) for support and locomotion medullary cavity filled with bone marrow. e.g. bones of forelimb & hindlimb including bones of the metacarpus/metatarsus and phalanges SHORT BONE Similar dimensions in length, breadth and Diffuse concussions; absorb cushions thickness; ranging from typical cube-shaped (6 surfaces) to compressed rods; have an outer layer of compact bone with a core of spongy bone and NO medullary cavity. e.g. carpals & tarsals FLAT BONE Large, expanded but thin area; have an outer For muscular attachments and for protection layer of compact bone with a layer of spongy of organs bone inside with NO medullary cavity inside. e.g. skull (DIPLOE), scapula, rib, pelvic bones IRREGULAR BONE Unpaired bones; ‘Jutting processes’ With varied functions; for support, for e.g. vertebral column, some bones of the skull articulation, protection and ligamentous attachment SPECIALIZED BONES Sesamoid bones Sesame-seed shaped bones that develop within To afford increased leverage; serve to a tendon (occasionally in a ligament) that runs change the angle at which the tendon passes over an underlying bony prominence. over the bone and thus reduce ‘wear and e.g. patella associated with the stifle joint; tear’ (reducing friction) fabellae Pneumatic bones Contain air-filled spaces known as paranasal The effect of reducing the weight of the sinuses bone e.g. maxillary and frontal bones Ribs Aberrant long bones Splanchnic bone e.g. os penis  Development of Bone o Ossification- the process by which bone is formed and that there are two types: INTRAMEMBRANOUS and ENDOCHONDRAL ossification. o The cells responsible for laying down new bone are called osteoblasts; the cells that destroy or remodel bone are called osteoclasts. The osteoblasts later become the osteocytes of mature bone.  Intramembranous ossification this is the process by the flat bones of the skull are formed. The osteoblasts lay down bone between two layers of fibrous connective tissue. There is no cartilage template. KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G en er al Ve te rin ar y Macr os copi c A na tomy : Os te olog y |5  Endochondral ossification involves the replacement of a hyaline cartilage model within the embryo by bone. The process starts in the developing embryo but is not completed fully until the animal has reached maturity and growth has ceased. Long bones of limb develop by this method.  External and Internal Structure of bone o DIAPHYSIS- the long shaft (body) of a long bone. Compact bone around the cavity. o EPIPHYSIS- the two enlarged ends (proximal and distal extremities) of a long bone; compact bone on the outside, spongy bone on the inside. o EPIPHYSEAL PLATE (Growth plate, physis) – a line of hyaline cartilage serving as the joining point of diaphysis and the epiphysis in a growing bone. o METAPHYSIS (Epiphyseal line)- the part of the epiphyseal cartilage being replaced by a bone. o PERIOSTEUM- the fibrous connective tissue covering around the bone (fresh state) that is not covered by articular cartilage. It is necessary for bone growth, repair, nutrition and attachment for ligaments and tendon.  Perichondrium- the connective tissue covering of cartilage. o ARTICULAR SURFACE- the smooth layer of hyaline cartilage covering the epiphysis where one bone forms a joint with another bone. o MEDULLARY CAVITY- The space in diaphysis containing the marrow. o MARROW- In the interstices of medullary cavity of long bones.  Red marrow several types of cells and is a blood- forming substance.  Yellow marrow replaces the red marrow and becomes an ordinary adipose tissue. o ENDOSTEUM- The fibrous and cel lular tissue lining the medullary cavity of the bone; similar in structure to periosteum but is thinner. It aids in repair of injury by providing cells (osteoblasts).  Over-repaired with bone of poor quality results in osseous bulges at the site of injury (exostoses). o MUCOPERIOSTEUM- covering of bones which participate in forming boundaries of the respiratory or digestive system; it lines all the paranasal sinuses and contain mucous cells. o COMPACT BONE- gross term for the part of the bone that looks solid. o CORTEX- compact bone surrounding the medullary cavity. o CANCELLOUS BONE (SPONGY) - consists of delicate bony plates and spicules running in different direction and intercross.  Physical Properties of Bone o One-third organic; two-thirds inorganic o Calcium phosphate- principal constituent of the inorganic matrix of bone. o Hydroxyapatite with adsorbed carbonate o Tricalcium phosphate hydrate  Vessels and Nerves of Bone o Nutrient (medullary) artery and vein compact substance (via nutrient foramen and canal of bone)marrow cavity subdivide supply the bone marrow & adjacent cortical bone. o Periosteal arteries and veins extremities of long bones and compact bone. o Lymph vessels in the periosteum as perivascular sheaths. o Nerves principally sensory.  Surface Contours of Bone (Bone Markings) o The bumps/eminences/projections, holes and depressions on a bone’s surface. o These markings can be either ARTICULAR or NONARTICULAR:  PROJECTIONS Articular Characteristic Examples Head A rounded articular process Head of the humerus or femur Condyle (G. knuckle) A large articular prominence Occipital condyles of the skull; condyles of humerus, femur and tibia KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G en er al Ve te rin ar y Macr os copi c A na tomy : Os te olog y |6 Nonarticular Characteristic Examples Process Any prominent, roughened projection Crest, spine, trochanter, tubercle, from a bone tuberosity Tuberosity/tuber A large, usually roughened process Ischiatic tuberosity, deltoid tuberosity Tubercle A small, rounded process Greater and lesser tubercles of the humerus Trochanter A large, blunt process Greater and lesser trochanter of the femur Spine (L. spina thorn) A sharp, slender process Spine of a vertebra, spine of scapula Crest A prominent border or ridge Crest of the hipbone, nuchal crest of the skull Neck Cylindrical part where head is attached Neck of the humerus and ribs Line A ridge less prominent than a crest Tricipital line of humerus Epicondyle (G. upon) A prominence just proximal to a condyle Lateral epicondyle of the humerus or femur  DEPRESSIONS Articular Characteristic Examples Glenoid cavity Shallow articular depression or Glenoid cavity of the scapula concavity Caudal articular surface of atlas Cotyloid cavity A deep articular depression Acetabulum of the hip joint Cranial articular surface of atlas Notch A depression at the edge of a bone Semilunar notch and radial notch of ulna, popliteal notch* of the tibia Trochlea A pulley-shaped structure Trochlea of the femur Facet (F. little faces) A smooth, flat surface covered with Articular facet of a thoracic vertebra for hyaline cartilage the attachment to a rib Fossa (L. pit) A small hollow Mandibular fossa of the temporal bone, olecranon* and radial* fossae of the humerus, masseteric fossa* of the mandible Nonarticular Characteristic Examples Fovea (L. pit) A shallow, non-articular depression Fovea capitis of the head of the femur; costal fovea and transverse fovea of the thoracic vertebra** Foramen (L. aperture) An opening (hole) through a bone Infraorbital foramen, obturator foramen, foramen magnum Canal A tunnel through one or more bones Vertebral canal Groove (L. sulcus, A long, narrow furrow accommodating a Brachial groove, grooves on the distal end furrow) vessel, nerve or tendon of the radius Meatus (L. a passage) A tube-like canal through a bone External auditory meatus Fissure A narrow, cleft-like opening between Tympano-occipital fissure, palatine fissure adjacent bones. *Non-articular; articular  THE AXIAL SKELETON o The bones and cartilages protecting the soft structures of the head, neck and trunk; consisting of:  SKULL- the bones of the face and the cranium.  HYOID APPARATUS- the bones holding the larynx in place and serving as a major attachment for the tongue. KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G en er al Ve te rin ar y Macr os copi c A na tomy : Os te olog y |7  VERTEBRAL COLUMN- or the backbone; composed of variable number of irregular bones that help in maintaining posture and participate in body movements; they also house and protect the spinal cord.  RIBS & STERNUM- thoracic bones protecting the thoracic organs. o THE SKULL  The most complex and specialized part of the skeleton.  It lodges the brain and houses the sense organs for hearing, equilibrium, sight, smell and taste while providing attachment for the teeth, tongue, larynx, and a host of muscles.  Divided into: Facial (plus palatal region) and Braincase (neural region) portions.  The facial and palatal region (36 bones) is the part enclosing the nasal and oral cavities.  Three terms used to designate head shapes: 1. Dolicocephalic meaning long, narrow-headed. 2. Mesaticephalic meaning a head of medium proportions. 3. Brachycephalic meaning short, wide-headed. o Individual Bones of the Skull Bones of the Braincase Paired Exoccipital, parietal, frontal, temporal Unpaired Supraoccipital, basioccipital, interparietal, basisphenoid, presphenoid, ethmoid Bones of the Face and Palate Paired Premaxilla, nasal, maxilla, dorsal concha, ventral concha, zygomatic, palatine, lacrimal, pterygoid, mandible Unpaired Vomer o Braincase (cranium, neural region) - the bones surrounding the brain forming the cranial cavity.  Separated from the nasal cavity by a perforated plate of bone, the cribriform plate.  Orbital cavities, at the junction of the facial and cranial parts, contain the globes of the eyes and accessory structures.  Regions of the braincase: 1. Roof of the cranium the dorsum (or calvaria) formed by the paired frontal and parietal bones; formed in membrane. 2. Occipital region the caudal aspect of the skull formed by the occipital bone; contains the foramen magnum allowing for the passage of the spinal cord and its associated vessels. 3. Temporal region the lateral walls of the cranium formed by the temporal bone. 4. Floor of the cranium the ventral aspect (basocranial axis) of the cranium formed primarily by the unpaired sphenoid bone; has a number of foramina for the passage of nerves and blood vessels; preformed in cartilage. 5. Rostral wall of the cranium the rostral aspect of the cranium formed by the unpaired ethmoid bone.  Bones of the braincase: KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G en er al Ve te rin ar y Macr os copi c A na tomy : Os te olog y |8 1. Occipital bone- the caudal aspect of both the cranial cavity and the skull as a whole; it forms a ring, the foramen magnum that develops from four centers—a squamos part (dorsal), two condylar parts (lateral) and a basilar part (ventral). Occipital bone Landmarks Supraoccipital (Squamos part)  Interparietal process Represents the unpaired interparietal  The largest division bone which fuses prenatally with the supraoccipital; rostral end is narrower and thinner than the caudal part  External sagittal crest Arises from the interparietal process, mid-dorsally.  Nuchal crest Unpaired transverse sharp-edged crest that marks the division between the dorsal and caudal surfaces of the skull.  External occipital protuberance The median, triangular projection forming the most dorsocaudal portion of the skull; the caudal process of the occipital bone.  External occipital crest A smooth median ridge extending from the external occipital protuberance to the foramen magnum.  Transverse canal  Internal occipital protuberance  Internal sagittal crest  Vermiform impression Forms the thinniest part of the caudal wall of the skull; an irregular excavation that houses a part of the vermis of the cerebellum.  Internal occipital crest Exoccipital condyles (2 Lateral  Occipital condyles Paired convex structures lateral to the parts) foramen magnum that articulate with  Bear the occipital condyles the atlas to form the atlanto-occipital joint.  Jugular (paracondylar) process Lateral to the condyle and projects ventrally.  Ventral condyloid fossa Between the jugular process and the occipital condyle.  Hypoglossal foramen Located rostral to ventral condyloid fossa; the external opening of the hypoglossal canal.  Dorsal condyloid fossa Dorsal to the occipital condyle.  Condyloid canal Runs through the medial part of the lateral occipital condyle. Basioccipital (Basilar part)  Intercondyloid notch  Unpaired and forms the  Pontine impression In the central area of the basioccipital. posterior third of the cranial  Foramen magnum Is a large, transversely oval opening in base the posteroventral portion of the skull, through which pass the spinal cord and its associated structures (meninges, vertebral venous sinuses, spinal portion of the accessory nerve, and arteries).  Nuchal tubercles Paired projections that are caudal extensions of the ventral part of supraoccipital bone.  Muscular tubercles Rough sagittally elongated areas, located medial to the smooth, rounded tympanic bullae.  Pharyngeal tubercle Single triangular rough area rostral to  the Intercondyloid incisure.  Petro-occipital canal 2. Parietal Bone (L. paries, wall) - is paired and together with the frontal bone forms the roof of the cranial cavity (dorsolateral). It articulates dorsally with its fellow and with the interparietal process of the occipital bone; forms the medial boundary of the temporal fossa. KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G en er al Ve te rin ar y Macr os copi c A na tomy : Os te olog y |9 3. Frontal bone (L. frons, forehead) - the rostral part of the roof of the cranial cavity; it is irregular in shape, being broad caudally and somewhat narrower rostrally; flares laterally to form the part of the temporal fossa. o Frontal sinus- an air cavity located between the inner and the outer tables of the rostral end of the frontal bone (divided into two or three compartments). o The frontal bone is divided into 4 parts: Orbital part Segment of a cone with the apex  Ethmoidal foramina located at the optic canal and the base  Supraorbital or zygomatic process forming the medial border of the  Fossa for the small lacrimal gland infraorbital margin. Temporal part Forms the part of the frontal bone caudal to the orbital part. Frontal part Roughly triangular, with its base facing medially, and articulating with that of the opposite bone. Nasal part The rostral extension of the frontal  Nasal process bone.  Septum of the frontal sinus 4. Sphenoid bones (G. sphen, wedge) - the unpaired bone forming the floor of the cranial cavity (rostral two- thirds of the base of the neurocranium, between the occipital caudally and ethmoid rostrally). o Consists of a pair of wings and a median body.  Presphenoid the more rostral bone with orbital wings.  Basisphenoid the caudal bone with the larger wings. 5. Temporal bone- Forms the caudolateral wall of the cranial cavity  Petrosal (pyramid/petrosum)- hardest bone; houses the inner ear (cochlea, vestibule, semicircular canal); mastoid process*  Tympanic (tympanicum)- tympanic bulla-> houses the middle ear (tympanic cavity)  Squamos- expanded plate, zygomatic process, mandibular fossa, retroarticular process 6. Ethmoid bone- the unpaired bone forming the rostral wall of the cranial cavity; located between the cranial and facial parts of the skull; situated between the walls of the orbits, it is bounded by the frontal bone (dorsally), maxillary (laterally) and vomer and palatine bones (ventrally). o It consists of four parts: a median perpendicular plate or lamina, two lateral masses covered by the external lamina and a cribriform plate.  FACIAL PART OF THE SKULL o The part enclosing the nasal and oral cavities. o Regions:  Oral region the incisive, maxillary and palatine bones and the mandible surrounding the oral cavity.  Nasal region the nasal, maxillary, palatine and incisive bones surrounding the nasal cavity.  Orbital region the bony socket holding the eye formed by portions of the frontal, lacrimal, palatine, sphenoid and zygomatic bones. o Bones of the face and palate  Incisive  Nasal bone  Maxillary bone  Dorsal nasal concha  Ventral nasal concha  Zygomatic bone  Palatine bone  Lacrimal bone  Pterygoid bone  Vomer  Mandible o Incisive (Premaxilla) Bone  The rostral bone holding the upper incisors (front teeth); has body and sockets o Nasal Bone  Forms the osseous roof of the nasal cavity along with the cranial part of the frontal bone.  It is long, slender, and narrow caudally. o Maxillary Bone (Maxilla)  The lateral part of the face and the part of the hard palate holding the upper cheek teeth.  The largest facial bone; divided into a body and 4 processes: 1. Frontal 2. Zygomatic 3. Palatine 4. Pterygoid  Infraorbital foramen for the passageway of infraorbital nerve and artery.  Alveolar process, Interalveolar septa, Interradicular septa o Dorsal Nasal Concha KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 10  Formerly the Nasal turbinate o Ventral Nasal Concha  Formerly the Maxilloturbinate; a scroll of bone located on the nasal cavity. Dorsal nasal Middle nasal Ventral Nasal Ventral nasal Concha meatus Concha meatus oZygomatic Bone (Malar or Jugal bone; L. mala, cheek)  Forms the cranial part of the zygomatic arch  Divided into 2 surfaces, 4 borders and 2 processes.  Surfaces: 1. Lateral convex 2. Medial/Orbital concave  Borders: 1. Maxillary 2. Temporal 3. Infraorbital 4. Masseteric  Processes 1. Temporal 2. Frontal  Orbital ligament it completes the orbit of the dog, caudally. It begins from the zygomatic process of the frontal bone (supraorbital process) and ends at the frontal process of the zygomatic bone. o Palatine Bone  Forms the caudal part of the hard palate; caudomedial to the maxilla.  Divided into: 1. Horizontal lamina forms the posterior third of hard palate; palatine and nasal surfaces; major and minor palatine foramina 2. Perpendicular lamina sphenopalatine foramen o Lacrimal Bone  In the rostral margin of the orbit; triangular in outline and pyramidal in shape. o Pterygoid Bone  Small, thin, slightly curved, nearly four-sided plate of bone in the caudal part of the nasopharynx. o Vomer Bone (Plowshare)  Unpaired bone forming the caudoventral part of the nasal septum.  It contributes to the roof of the choanae having sagittal and horizontal parts. o Mandible (L. Mandere, to masticate; Lower jaw bone)  The large bone articulating with the skull that supports all the lower teeth.  Largest bone of the skull; the only mobile.  The two halves united by symphysis.  Each half is divided into: 1. Body the horizontal part bearing all the lower teeth; alveolar border; mental foramina—rostral, middle (the largest) and caudal—on the rostro-lateral aspect. 2. Ramus the vertical caudal part bearing no tooth; it has the mandibular foramen on its medial aspect.  Three processes a. Coronoid b. Condyloid (articular) smooth and articulates with the mandibular fossa of the temporal bone to form the temporomandibular joint. c. Angular  IMPORTANT FORAMINA IN THE SKULL OF DOGS OPENINGS STRUCTURES PASSING THROUGH Infraorbital foramen Infraorbital nerve Maxillary foramen Infraorbital nerve Cribriform foramina Olfactory nerve Optic canal Optic nerve Orbital fissure Cranial nerve III, IV and ophthalmic division of Cranial nerve V and VI Round foramen Maxillary division of Cranial nerve V Foramen lacerum Internal carotid artery Internal acoustic meatus Cranial nerve VIII Jugular foramen Cranial nerves IX, X & XI Tympano-occipital fissure Cranial nerves IX, X & XI Stylomastoid foramen Cranial nerve VII Mandibular foramen Mandibular alveolar nerve KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 11 Mental foramen Mandibular alveolar nerve  Paranasal sinuses o Maxillary sinus (recess) - in the maxillary bone which forms a large diverticulum of the nasal cavity.  Boundaries: 1. Medial limit lateral lamina of the ethmoid bone 2. Lateral limit maxillary, palatine and lacrimal bones o Frontal sinus- between the outer and inner tables of the frontal bone.  Parts: 1. Lateral forms the whole enlargement of the frontal bone. 2. Rostral unites the two tables of the frontal bone. 3. Medial more irregular. o Sphenoidal sinus- lies within the presphenoid bone occupied by endoturbinate.  Bones of the Hyoid Apparatus o Hyoid Apparatus (G. hyoedes, u-shaped) – a number of connected (through synchondroses) bones acting as a suspensory mechanism for the tongue and larynx; attaches to the mastoid process of the skull dorsally (via the tympanohyoid cartilage) and to the larynx and base of the tongue ventrally, suspending these structures in the caudal part of the mandibular space.  Consists of: thyrohyoid, basihyoid, ceratohyoid, epihyoid, stylohyoid and tympanohyoid  Thyrohyoid (the cornus maju of man), is laterally bowed, sagitally compressed, slender element which extends dorsocaudally from the basihyoid to articulate with the cranial cornu of the thyroid cartilage of the larynx.  Basihyoid transverse unpaired element lying in the musculature of the base of the tongue as ventrally bowed, dorsoventrally compressed rod.  Ceratohyoid is a small, short, tapered rod having a distal extremity which is about as large as its proximal extremity; articulates with the basihyoid and the thyrohyoid; the proximal extremity articulates with the epihyoid.  Epihyoid parallel to the thyrohyoid bone; articulates with the ceratohyoid distally and with stylohyoid proximally.  Stylohyoid slightly longer than the epihyoid, with which it articulates.  Tympanohyoid cartilage is a small cartilaginous bar which continues the proximal end of the stylohyoid to the mastoid process of the skull.  The Vertebral Column (Spine/Backbone) o Consists of approx. 50 irregular bones (vertebrae) which protects the spinal cords, supports the head and serves as attachment for the muscles effecting body movements. o It extends from the skull through the tail; the joints formed by the vertebrae allow a great amount of movement. o Vertebrae- the irregularly-shaped bones making up the spinal column. They are arranged in five groups:  Cervical (neck), Thoracic (cranial back), Lumbar (loin) and Caudal/Coccygeal (tail) vertebrae.  Each group is represented by its first letter followed by the number representing how many are in each section.  C7 T13 L7 S3 Cd2023 vertebral formula of the dog  All the vertebrae except the sacral vertebrae remain separated and articulate with contiguous vertebrae forming movable joints.  Sacrum a single bone formed by the fused three sacral vertebrae. o Structure of a typical vertebra: body, arch, vertebral foramen and processes.  Body- thick, constricted centrally; has slightly convex cranial articular surface and a centrally, depressed concave caudal articular surface. o Intervertebral fibrocartilage (disc) connects the bodies of adjacent vertebrae. o Pulpy nucleus (nucleus pulposus) at the center of the disc. o Fibrous ring (annulus fibrosus) at the outer portion of the disc; attaches firmly to adjacent vertebrae.  Vertebral arch (neural arch) - the dorsal part of a vertebra arising from the body; consists of two upright pedicles forming the walls of the vertebral foramen and two laminae projecting to the midline and forming the roof of the vertebral foramen; together with the body, forms the vertebral foramen. o Vertebral foramina forms the vertebral canal; the space formed by the vertebral arch and the body. o Vertebral canal formed in the live animal by all the vertebral foramina housing the spinal cord. o Cranial vertebral notch o Caudal vertebral notch o Intervertebral foramina the opening between vertebrae formed by the caudal and cranial notches of adjacent vertebra; allow passage of the spinal nerves.  Processes (7) - provide sites for muscle attachment; the others form synovial joints with adjacent vertebrae. 1. Spine (Spinous process) - the dorsal projection of the vertebral arch; formed at the midline by the right and left lamina of the dorsal part of vertebral arch. 2. Transverse process- lateral extension of the vertebral arch; irregularly shaped lateral projection from the region where the pedicle joins the vertebral body; divides the muscles of the back into dorsal (epaxial) and ventral (hypaxial) groups.  Transverse foramen- at the root of the transverse processes in the cervical region, dividing the process into dorsal and ventral parts. KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 12 3. Articular processes (4) - paired; present at both the articular cranial and the caudal surface of a vertebra, at the junction of the root and lamina.  Cranial process (prezygaphosis) - faces craniodorsally or medially.  Caudal process (postzygaphosis) - faces caudoventrally or laterally. o CERVICAL VERTEBRAE (Cervix, neck) - seven in number in most mammals, characterized by a transverse foramen (except for C7); the first two (Atypical), differing greatly from each other and also from all other vertebrae, can be readily recognized.  Atlas o The first cervical vertebra, named for its support of the head; atypical in both structure and function (reduction of a body and absence of spinous process). o It articulates with the skull cranially and with the axis caudally. o Chief peculiarities: 1. Modified articular processes which cup the exoccipital condyles 2. Winglike lateral expansions 3. Lack of spinous process 4. Reduction of its body (formed by the ventral arch). o Massae laterales the thick lateral portions of the atlas. o Ventral arch the portion of the atlas replacing the body of other vertebrae. o Wings (alae) the large, shelflike modified transverse processes projecting from the lateral masses. o Dorsal and ventral tubercles bifid and conical structures, respectively, found on the vertebral arch and body. o Cranial articular surface two condyloid cavities articulating with the occipital condyles of the skull forming the atlanto-occipital joint (yes joint). o Caudal articular surface two shallow glenoid cavities articulating with the axis forming the atlanto-axial joint (no joint). o Fovea of the dens at the dorsal surface of the body of atlas articulating with the dens of the axis. o Transverse foramen a short canal passing obliquely through the transverse process or wing. o Lateral vertebral foramen perforates the craniodorsal part of the vertebral arch. o Cranial and caudal notches o Atlantal fossae depressions ventral to the wings; traversed by the vertebral vein and artery.  Axis o Second cervical vertebra/Epistropheus o Presents an elongated, dorsal spinous process—bladelike cranially and expanded caudally; overhangs the cranial and caudal articular surfaces of the vertebral body. o Characterized by the DENS (odontoid process) a cranioventral peglike eminence. o Cranial and caudal articular surfaces o Cranial and caudal vertebral notches  Third, Fourth and Fifth Cervical Vertebrae o Spinous process increase in length from C3C5. o Strong laminae on the C3, but gradually become shorter and narrower on the remaining ones. o Tubercles on the caudal articular processes—decreasing in prominence from C3C7 segment. o The transverse processes of C5 are the shortest.  Sixth Cervical Vertebra o Possesses a higher spine than the C3, C4 and C5. o Main peculiarity: expanded platelike transverse processes. **In contrast to all other vertebrae, the first six cervical vertebrae are characterized by TRANSVERSE FORAMEN.  Seventh or Last Cervical Vertebrae o Lacks transverse foramina. o Cervical ribs articulate with the ends its single-pronged transverse processes. o The spine is the highest of all those on the cervical vertebrae. o Rib foveae appear caudoventral to the caudal vertebral notches. o **Pleurapophyses fused ribs represented by the transverse processes of cervical vertebrae. o THORACIC VERTEBRAE  The vertebrae of the thorax, characterized by articular facets (foveae) for the pair of ribs they bear.  Thirteen in number; the first nine are similar, the last four present minor differences from the other.  Bodies are shorter than those of the cervical or lumbar region; slightly less than a third longer than lumbar region; the pedicles of the vertebral arches are short.  The two costal foveae: o Costal Fovea or DEMIFACET two facets for articulation with a rib’s head. **The heads of the first ribs articulate with the cranial part of the body of T1 and with the fibrocartilage between C7 and T1. o Transverse costal fovea the facet on the transverse process that articulates with the tubercle of the same numbered rib.  Spinous process o The laminae give rise to a spinous process—the most conspicuous feature of the first nine thoracic vertebrae. o The spine of T11 is nearly perpendicular to the long axis of the bone—the ANTICLINAL vertebra the transitional segment of the thoracolumbar region. o All the spines caudal to those of T12 and T13 are directed cranially, whereas the spines of all vertebrae cranial to T11 are directed caudally. KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 13  Transverse processes Are short, blunt and irregular; all contain foveae for articulation with the tubercles of the ribs. o These foveae decrease in size and convexity from T1T13. o  Mamillary processes (Metapophyses) o Small knoblike eminences projecting dorsally from the transverse processes. o Start at T2 or T3 and continues as paired projections through the remaining part of the thoracic, lumbar, sacral and coccygeal regions. o At T11 they become associated with the cranial articular processes.  Accessory processes (Anapophyses) o Appear first in the midthoracic region and are located on succeeding segments as far caudally as the L5 or L6 vertebrae.  Articular processes o Located at the junctions of the pedicles and the laminae. o LUMBAR VERTEBRAE (Fr. Lumbus, loin)  The vertebrae (seven in number) of the lumbar (lower back, loin) region, characterized by their large size and long plate-like transverse process.  Can be distinguished from the last thoracic vertebrae by their lack of costal facets.  Spinous processes- are highest and most massive in the midlumbar region.  Transverse processes- are directed cranially and slightly ventrally; longest in the midlumbar region.  Accessory processes- are well-developed on the first three or four lumbar vertebrae and absent on the fifth or sixth.  Articular processes- lie mainly in sagittal planes; all cranial articular processes bear mamillary processes. o SACRAL VERTEBRAE  The bodies and processes fused in the adult to form the SACRUM; the bulk lies between the ilia and articulates with them.  The body of the first segment is larger than the bodies of the other two segments combined.  Dorsal surface: o Median sacral crest in the dorsal surface representing the fusion of the three spinous processes. o Dorsal sacral foramina transmit dorsal division of sacral nerves and vessels. o Intermediate sacral crest o Lateral sacral crest o Caudal and cranial articular processes.  Pelvic surface: o Variable in its degree of concavity  Wing of the sacrum o The enlarged lateral part which has a large, rough semilunar facet, the auricular surface which articulates with the ilium.  Base of the sacrum o Sacral canal o Promontory a transverse ridge at the cranioventral part of the base; along with the ilia, forms the dorsal boundary of the smallest part of the bony ring, or pelvic inlet, through which the fetus passes during birth. o Sacrovertebral angle o CAUDAL VERTEBRAE (also coccygeal vertebrae)  Is usually 20—may vary from 6 to 23.  Body  Vertebral arch first develop in the first caudal segment; cranial articular processes have lost their articular function; mamillary process; caudal articular processes.  Hemal arches are present as separate bones which articulate with the ventral surface of the caudal ends of the bodies of the Cd4-Cd6; slope caudally and are shaped like a V or Y, they protect the median coccygeal artery; caudally are the paired hemal processes which are the last processes to disappear.  THE THORAX o The bony cavity formed by the sternum, the ribs, the costal cartilages, and the bodies of the thoracic vertebrae.  The Ribs (Costae) o The long, curved bones forming the lateral wall of the thorax; 13 pairs in dog. o Divided into:  Bony part at the dorsal part, laterally and caudally convex.  Cartilaginous part at the ventral part. o True ribs (STERNAL) articulate directly by their costal cartilage with the sternum. o False ribs (ASTERNAL) all ribs that are not true ribs; their costal cartilages unite to form the costal arch.  Floating ribs last false ribs (dog & man); end in costal cartilage not joining to sternum or other costal cartilage. o Structure of a typical rib: vertebral and sternal extremities plus an intermediate body or shaft.  Vertebral extremity 1. Head has a wedge-shaped articular surface articulating with adjacent costal foveae of thoracic vertebrae and intervening fibrocartilage. 2. Neck KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 14 3.Tubercle bears an articular facet for articulation with the transverse process of the vertebra of the same number; Costotransverse foramen the space between the neck and tubercle of the rib and the body of the vertebra.  Body- is cylindrical and slightly enlarged at the costochondral junction. 1. Anglean indistinct lateral eminence distal to the tubercle. 2. Costal groove on the inner surface, for the intercostal vessels and nerve.  Costal cartilage- the cartilaginous cylindrical distad continuation of the bony rib; the costal cartilages of the tenth, eleventh and twelfth are long, slender rods each joined to the one above by connective tissue to form the costal arch. **The costal cartilages of the tenth, eleventh and twelfth ribs unite with the cartilage of the rib above to form the costal arch. **The ninth ribs are the longest, with the longest costal cartilages. o Intercostal space the space between adjacent ribs; are two or three times as wide as the adjacent ribs.  The Sternum o An unpaired segmental series of eight bones (sternebrae; sternal segments) forming the floor of the thorax. o Slightly turned up in front and turned down behind. o Intersternebral cartilages short blocks of cartilage joining the consecutive sternebrae. o Manubrium sterni (Presternum; L. handle) the first sternebra; is longer than the others. o Xiphoid process (G. xiphos, sword) the last sternebra; is wide horizontally and thin vertically. o Xiphoid cartilage a thin cartilaginous plate prolonging the xiphoid process caudally.  THE APPENDICULAR SKELETON o Bones of the Thoracic/Pectoral Limb  Pectoral girdle- clavicle and scapula  Arm or brachium- humerus  Forearm or antebrachium- radius and ulna  Forepaw or manus- wrist/carpus, metacarpals, phalanges and palmar sesamoid bones. THORACIC GIRDLE (Shoulder Girdle) 1. Two scapulae **The girdle connects the bones of the arm to the axial skeleton by 2. Clavicle muscular attachments (SYNSARCOSIS), and not by an articulation. 3. Coracoid o CLAVICLE  Is not articulated with the skeleton.  Located at the tendinous intersection of the brachiocephalicus muscle; over 1 cm long, thin and slightly concave both longitudinally and transversely. o SCAPULA (Shoulder Blade)  The large triangular, flat bone of the shoulder; the highest part lies just below the level of the free end of the spine of T1 or T2. Surfaces Borders Angles LATERAL CRANIAL CRANIAL Spine of the scapula Scapular notch Acromion Supraspinous fossa Infraspinous fossa MEDIAL DORSAL CAUDAL Facies serrata Scapular cartilage Subscapular fossa CAUDAL VENTRAL Infraglenoid tubercle Glenoid Cavity Supraglenoid tuberosity Coracoid process  Lateral Surface: o Spine of the scapula the long projection of a bone dividing the lateral surface into two nearly equal fossae; it’s the most prominent feature of the lateral surface of the bone. o Acromion (hamate process) the expanded distal end of the spine of the scapula. o Supraspinous fossa the area cranial to the spine; bounded by the cranial surface of the scapular spine and the adjacent lateral surface of the scapula. o Infraspinous fossa the area caudal to the spine; triangular.  Medial/Costal Surface: o Lies opposite the first five ribs and the adjacent four or five thoracic vertebrae. o Facies serrata a small dorsocranial rectangular area. o Subscapular fossa the large remaining part of the surface, nearly flat and presents three relatively straight muscular lines which converge toward the distal end of the bone.  Cranial Border: KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 15 o Thin except at extremities; distally, smoother and thicker; proximally, rougher ang thicker. o Scapular notch a concavity at the distal part marking the position of the constricted part of the bone.  Dorsal/Vertebral Border: o The Base; extends between the cranial and caudal angles. o Scapular cartilage a narrow band capping this border and represents the unossified part of the bone.  Caudal Border: o The thickest of the three borders and bears the infraglenoid tubercle. o Infraglenoid tubercle a projection just dorsal to the ventral angle; located largely on the costal surface of the bone and is thicker than the border.  Caudal Angle: o Is obtuse as it unites the adjacent thick and caudal border with the thinner, rougher, gently convex vertebral border (origin of the teres major muscle).  Cranial Angle: o Unites the cranial border to the dorsal (vertebral) border; no muscles attach directly to the cranial angle.  Ventral Angle: o Formerly called the articular, glenoid, or lateral angle o Forms the expanded distal end of the scapula. o It’s the most important part of the bone, since it contains the glenoid cavity. o Glenoid cavity receives the head of the humerus in forming the shoulder joint; it’s very shallow. o Supraglenoid tuberositythe largest tuberosity of the scapula (origin of the tendon of biceps brachii muscle) near the cranial aspect of the concavity. o Coracoid process (G. crowlike) a remnant of the coracoid bone, it’s a beaklike process on the medial side of the supraglenoid tubercle. o HUMERUS (Arm or Brachial Bone)  The largest bone of the thoracic limb.  The bone of the arm or brachium; proximally it articulates with scapula (shoulder joint) and distally with the radius and ulna (elbow joint).  Divided into a shaft and two extremities. Proximal Extremity Shaft/Body Distal Extremity Head LATERAL SURFACE Humeral condyles (Articular Greater tubercle Deltoid tuberosity areas) Lesser tubercle Tricipital line Lateral epicondyle Neck Brachial (Musculospiral) Medial epicondyle Intertubercular (Bicipital) groove Lateral epicondylar crest groove Radial fossa Crest of greater tubercle MEDIAL SURFACE Olecranon fossa Tuberosity for teres minor Tuberosity for teres major Supratrochlear foramen  Proximal Extremity o Head oval, being elongated in a sagittal plane, it is the rounded process articulating with the glenoid cavity of the scapula. o Lesser (Medial, Minor) tubercle the flattened process on the medial side of the head. o Greater (Lateral, Major) tubercle the large process craniolateral to the head; a smooth convex summit higher than the head. o Intertubercular groove (Bicipital groove) distal to the head; a sulcus between tubercles. o Neck of the humerus distinct only caudally and laterally, it indicates the line of fusion of the head and the tubercles with shaft.  Body of the humerus or the shaft, is the long, slightly sigmoid-shaped part of the humerus which unites the two extremities; posseses lateral and medial surfaces. o Lateral surface: 1. Tricipital line formerly the anconeal line; begins at the head caudal to the greater tubercle and extends caudally to the deltoid tuberosity. 2. Deltoid tuberosity the most prominent feature of the lateral surface of the humerus, it is the large tuberosity on the cranio-LATERAL side. 3. Brachial (musculospiral) groove forms the smooth, flat to convex, lateral surface of humerus. o Medial surface: 1. Crest of lesser tubercle (insertion for coracobrachialis muscle). 2. Tuberosity for the teres major (insertion for teres major and latissimus dorsi muscles). o Cranial surface: 1. Crest of greater tubercle (insertion for superficial pectoral muscle).  Cranial surface begins proximally at the crest of the greater tubercle  medial to deltoid tuberosity cranial end of brachial groove. o Caudal surface: 1. Neck of the humerus  Caudal surface begins at the neck of the humerus lateral epicondyloid crest.  Distal Extremity KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 16 o Humeral condyle- the distal end of the humerus including its articular areas, the adjacent fossae and the two epicondyles. 1. Capitulum humeri a small, lateral articular area for articulation with the head of the radius. 2. Trochlea humeri a much larger, medially located pulley-shaped part extending proximally into the adjacent fossae; articulates with the trochlear notch of the ulna. o Lateral epicondyle (extensor epicondyle) the enlarged part in the lateral side of the humeral condyle.  Lateral epicondylar crest extends proximally from the lateral epicondyle. o Medial epicondyle (flexor epicondyle) larger than the lateral epicondyle, it is the medial-most point of the humerus. o Olecranon fossa a deep excavation of the caudal part of the distal extremity of the humerus; it receives the anconeal process of the ulna; it is covered by the anconeus muscle. o Radial fossa (coronoid fossa) opposite the olecranon fossa. o Supratrochlear foramen the means by which the olecranon and radial fossae communicate with each other; nothing passes through it. o RADIUS ((L. spoke of a wheel)  The main weight-supporting bone of the forearm; shorter than the ulna and serves primarily for muscle attachment.  It articulates with the humerus and ulna (elbow joint) proximally and the carpal bones and ulna (antebrachiocarpal joint) distally.  It is divided into: proximal and distal extremities with a shaft or body. Proximal Extremity Shaft/Body Distal Extremity Head (articular fovea, articular Two surfaces (cranial & caudal) Carpal articular surface circumference) Two borders (lateral & medial) Ulnar notch Neck Radial tuberosity Styloid process Three grooves (cranial aspect; dorsal surface)  Proximal Extremity o Head irregularly oval in outline as it extends transversely across the proximal end of the bone. 1. Articular fovea concave and articulates with the capitulum of the humerus; bears practically all the weight transmitted from the arm to the forearm. 2. Articular circumference is a caudal, smooth, osseous band on the head for articulation with the radial notch of the ulna. o Neck the constricted segment of the radius which joins the head to the body.  Body or shaft presents two surfaces (cranial/caudal) and two borders (lateral/medial). o Radial tuberosity a small projection distal to the neck on the medial border and adjacent caudal surface.  Distal Extremity is the most massive part of the bone. o Carpal articular surface the trochlea at the distal surface articulates with the carpal bones. o Ulnar notch at the lateral surface articulates with articular circumference of the ulna. o Styloid process medially, it extends distal to the main carpal articular surface in the form of a sharp, wedge- shaped projection. o Cranial Aspect presents three grooves: 1. Medial groove the most medial, short and distinct (for the tendon of abductor pollicis longus) 2. Middle groove the largest (for the tendon of the extensor carpi radialis) 3. Lateral groove the most lateral groove (for the tendon extensor digitorum communis) o ULNA (L. elbow)  The long, thin bone; the longest bone in the body.  For muscle attachment and articulation.  Proximally it articulates with humerus and radius; distally with the radius and carpal bones.  Two extremities plus a body. Proximal Extremity Shaft/Body Distal Extremity Olecranon Cranial surface Articular circumference Anconeal process Interosseous border Styloid process Trochlear (Semilunar) notch Caudal border Coronoid (Medial/Lateral) Caudal surface process Ulnar tuberosity Radial notch Medial Border Lateral Border  Proximal Extremity o Olecranon provides lever arm (tension process) for the extensor muscles of the elbow; it forms the POINT OF THE ELBOW. o Anconeal process  the proximal end of the trochlear notch which fits in the olecranon fossa of the humerus during elbow extension. o Trochlear (Semilunar) notch  smooth, vertical, half-moon shaped concavity facing cranially and ends in the anconeal process; articulates with humerus. KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 17 o Coronoid process  the large distal end of the trochlear notch, divided into medial and lateral projections (articular). o Radial notch  articulates with the articular circumference of the radius.  Body/Shaft is compressed laterally in its proximal third, three-sided throughout its middle third, and cylindrical in its distal end. o Cranial surface rough and convex for the attachment of the interosseous ligament. 1. Interosseous border o Caudal border smooth and concave. o Caudal surface 1. Ulnar tuberosity roughened part located near the proximal end of the caudal surface just distal to the trochlear notch. o Medial and lateral borders  Distal Extremity is separated from the body of the bone by a notch in its cranial border. o Articular circumference  distal to the notch and articulates with the ulnar notch of the radius. o Styloid process  the pointed, distal end of the ulna; has two facets for articulation– with ulnar carpal bone and accessory carpal bone. o Interosseous space  the space between the ulna and the radius. Always remember these important landmarks in the radius and ulna that connect them together! Radius and Ulna Connection Radius Ulna Proximal radioulnar joint Articular circumference Radial notch Distal radioulnar joint Ulnar notch Articular circumference o THE FOREPAW (Manus)  Carpus (wrist)  carpal bones  Metacarpus  metacarpal bones  Phalanges Sesamoid bones o Carpus  Includes the carpal bones and the associated sesamoid bones.  The compound joint formed by these bones.  The region between the forearm and metacarpus. o CARPAL BONES (7) Proximal Row Distal Row Radial carpal (Scaphoid) First carpal (Trapezium) Ulnar carpal (Triquetrum) Second carpal (Trapezoideum) Accessory carpal (Pisiforme) Third carpal (Capitatum) Fourth carpal (Hamatum) **In dogs, the intermediate carpal bone is fused with the radial carpal bone, thus the other name for the bone is intermedioradial carpal bone.  Radial Carpal (SCAPHOID) o The largest carpal bone located on the medial side of the proximal row. o The proximal surface articulates with the distal end of the radius. o The distal surface articulates with all four carpal bones. o Laterally articulates with the ulnar carpal.  Ulnar Carpal (TRIQUETRUM) o Lateral bone of the proximal row; smaller than radial carpal. o Proximally articulates with ulna and radius. o Distally articulates with fourth carpal and fifth metacarpal. o Medially articulates with radial carpal. o On the palmar side, with accessory carpal.  Accessory Carpal (PISIFORME) o A truncated bone located behind (palmar) the carpus. o Articulates with the ulnar carpal.  First carpal bone (TRAPEZIUM) o The smallest carpal bone. o It articulates with the palmaromedial surfaces of the second carpal and the base of metacarpal II. o Proximally articulates with radial carpal and distally with metacarpal I.  Second carpal bone (TRAPEZOIDEUM) o A small, wedge-shaped, proximodistally compressed bone. o Proximally articulates with the radial carpal. o Distally with metacarpal II. o Laterally with third carpal. o Medially with first carpal. KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 18  Third carpal bone (CAPITATUM) o Larger than the second carpal. o Its large palmar projection articulates with three middle metacarpal bones. o Medially articulates with second carpal. o Laterally articulates with fourth carpal. o Proximally articulates with radial carpal. o Distally articulates with metacarpal III.  Fourth carpal bone (HAMATUM) o The largest bone of the distal row. o Distally articulates with metacarpals IV and V. o Medially with the third carpal. o Proximomedially with radial carpal. o Metacarpus  The region of the manus located between the carpus and digits.  Has five metacarpal bones numbered I-V from medial to lateral.  Each bone is composed of a base (articulates with carpus), a head (articulates with proximal phalanx of a digit) and a shaft.  Two sesamoid bones with each bone.  First Metacarpal Bone o The shortest and most slender of the metacarpal bones. o It bears the first digit. o Proximally articulates with first carpal. o Laterally articulates with second metacarpal. o Distally, its trochlea articulates with the proximal phalanx of the first digit and a single palmar sesamoid bone.  Metacarpal bones II-V o The main metacarpal bones; irregular rods with a uniform diameter. o Digits  The digital skeleton of the forepaw; five units (I-V) numbered from medial to lateral; four are fully developed and one is rudimentary.  Generally consist of three phalanges and sesamoid bones. 1. Proximal phalanx 2. Middle phalanx 3. Distal phalanx  Proximal Phalanx o The first phalanx divided into the base, body and head. o From II to V is a medium-length rod with enlarged extremities.  Middle Phalanx o The second phalanx with the same structure as the proximal phalanx, but shorter. o It is not present in the first digit.  Distal Phalanx o The third phalanx that is approx. of the same size in all four main digits. o Carries the horny claw. o Flexor process  on the palmar side o Extensor process  dorsal proximal part.  The DEWCLAW o The 1st digit (proximal and distal) and the first metacarpal bone. o SESAMOID BONES  Palmar sesamoid bones  on the palmar surface of each metacarpophalangeal joint of the main digits.  Distal sesamoid bones  represented by cartilages and rarely ossify.  BONES OF THE PELVIC LIMB o Pelvic girdle (Os coxae) o Thigh (Femur) o Stifle (Patella, Fabellae) o Leg or crus (Tibia and Fibula) o Pes (Tarsal, Metatarsals, Digits, Sesamoid bones) o The PELVIC GIRDLE (Bony Pelvis)  Encloses the pelvic cavity—pelvic inlet (cranial opening) & pelvic outlet (caudal opening). 1. Two hip bones (ossa coxarum) 2. Sacrum 3. First few caudal vertebrae o OS COXAE (Hip Bone)  The fused (12th postnatal week) ilium, ischium, pubis and acetabulum.  The two hip bones (ossa coxarum) are joined at the pelvic symphysis. o Ilium  The largest and most cranial of the bones of the os coxae.  Consists of: Body and Wing  Body (Cranial Border) o Iliac crest  forms a cranially protruding arc; ventral half is thin, the dorsal half is increasing in thickness.  Body (Dorsal border) KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 19 o Greater ischiatic notch  a concave in the caudal half of the dorsal border. o Ischiatic spine  a convex that is continues with the dorsal border of the ilium with dorsal border of the ischium; it separates the greater and lesser ischiatic notches.  Tuber Sacrale  the medial process of the wing next to the sacrum. 1. Caudal dorsal iliac spine 2. Cranial dorsal iliac spine  Tuber Coxae  the palpable prominence on the lateral wing. 1. Cranial ventral iliac spine 2. Caudal ventral iliac spine  Wing o Gluteal surface  faces laterally and slightly upward. o Sacropelvic surface  the auricular surface articulating with the sacrum (sacroiliac joint). o Iliac tuberosity  rough, slightly protruding eminence of the sacropelvic surface located dorsal to auricular surface. o Iliac surface  nearly square, flat area cranial to the auricular surface. o Arcuate line  from the auricular surface to the iliopubic eminence. o Ischium  The caudal most part of the os coxae.  It enters into the formation of the acetabulum, obturator foramen and symphysis pelvis.  Consists of: 1. BODY 2. RAMUS 3. TUBEROSITY  Body is lateral to the obturator foramen. o Ischiatic spine o Lesser ischiatic notch caudal to the ischiatic spine.  Ramus joins the body at a right angle to form the following: o Ischiatic table  facing dorsally. o Ischiatic arch  joined by the joining of the caudomedial parts of the two ischii.  Tuberosity o Ischiatic TUBEROSITY  the thick, caudal part (ventral surface in particular) of the ischium giving rise to the hamstring muscles of the thigh. o Pubis  The cranioventral part of the os coxae, extending from the ilium and ischium laterally to the symphysis pubis medially.  Consists of a central body and two branches (rami).  Body o The central part of the bone forming the cranial border of the obturator foramen; fuses side by side to form the symphysis pubis.  Ramus o Cranial ramus  forms a part of the acetabulum. o Iliopubic eminence  at the cranial end of the ramus as it joins the ilium. o Caudal ramus  medial to the obturator foramen; it extends to the ischium, where it fuses without demarcation. o Iliopectineal eminence  on the cranial border of the bone as it joins the ilium. o Pubic tubercle  on the ventral surface of the pubic symphysis. o Pecten  the medial part of the arcuate line on the cranial border of the pubis. o Acetabulum (L. vinegar cup)  The deep concavity articulating with the femoral head.  Formed by the fusion of the ilium, ischium, pubis and acetabular bones. o Lunate surface  the smooth articular circumference which is deficient over the medial portion of the acetabulum. o Acetabular notch  indentation at the medial part of the acetabulum. o Acetabular fossa  the quadrangular, non-articular, thin, depressed area extending laterally from the acetabular notch. o Acetabular bones  located on the floor of the acetabulum; it becomes incorporated with the larger bones during the 7th postnatal week. o PELVIC CAVITY  Must be large enough to allow for the passage of the young during parturition.  Cranial pelvic aperture (Pelvic Inlet): 1. Promontory of the sacrum (dorsal) 2. Cranial border of the pubis or pecten (ventral) 3. Arcuate line (bilateral)  Caudal pelvic aperture (Pelvic Outlet): 1. First caudal vertebra (dorsal) 2. Sacrotuberous ligament (bilateral) 3. Tuber ischiadicum (ventral) and the ischiatic arch in between them. o Obturator Foramen  The large oval to triangular opening in the floor of the os coxae. o Symphysis pelvis KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 20  Median synostosis formed by the right and left pubic and ischial bones. 1. Symphysis pubis (cranially) 2. Symphysis ischii (caudally) o FEMUR (Thigh bone)  The heaviest bone in the skeleton.  It articulates proximally with the hipbone (hip joint) and distally with the tibia (stifle joint).  Extremities and a Shaft Proximal Extremity Shaft/Body Distal Extremity Head Lateral and medial surfaces Medial and Lateral Condyles Fovea capitis femoris CRANIAL (G. Knuckles) Neck Line of vastus lateralis Intercondylar fossa Greater trochanter Line of vastus medius Femoral trochlea (Patellar Lesser trochanter CAUDAL surface) Intertrochanteric crest Femoral lips (Medial & Medial and Lateral Third trochanter Lateral) Epicondyles Transverse line Popliteal surface Extensor fossa Trochanteric surface Medial and Lateral supracondylar tuberosities  Proximal Extremity oHead a smooth, nearly hemispherical process articulating with the acetabulum of the os coxae. oFovea capitis femoris a small, indistinct, circular pit on the medial part of the head for the round ligament of the femur. o Neck  joins the head to the body of the femur. o Greater (Major, Lateral) Trochanter  the largest tuber of the proximal extremity lateral to the head and neck. o Trochanteric fossa  depression on the caudal aspect of the femur between the trochanters. o Lesser (Minor, Medial) Trochanter distinct, pyramid-shaped eminence distal to the head. o Intertrochanteric crest a low but wide arciform crest connecting the lesser trochanter with the greater trochanter. o Third Trochanter the prominence on the lateral side, distal to the greater trochanter. o Transverse Line dorsally arched and runs from the femoral head across the cranial surface of the intertrochanteric crest to the greater trochanter.  Shaft/Body o Cranial, lateral and medial surfaces are not distinct from each other but the caudal surface is flatter than the others. o Caudal surface  Facies aspera finely roughened surface bounded by the medial and lateral lips (femoral lips) diverging proximally and laterally.  Popliteal surface sagittally concave, transversely flat area enclosed distally by the femoral lips.  Trochanteric surface flat surface proximally enclosed by the femoral lips.  Distal Extremity is quadrangular and protrudes caudally. o Lateral Condyle convex in both the sagittal and the transverse plane. o Medial Condyle smaller and less convex in both the transverse and the sagittal plane. ** Each condyle articulates with the tibia and the menisci. **On the caudal proximal surfaces are facets for articulation of the medial and lateral fabellae. o Femoral trochlea (Patellar surface)  smooth, wide groove on the cranial surface of the distal extremity articulating with the patella or knee cap; bounded by medial and lateral ridges. o Medial and Lateral Epicondyles  proximal and cranial to the condyles serving for the proximal attachment of the medial and lateral collateral ligaments of the stifle joint. o Extensor Fossa  a small depression (pit) between the junction of the lateral ridge of the patellar surface and the lateral epicondyle. o Medial and Lateral supracondylar tuberosities  tubercles at the proximal edge of the popliteal surface. o Sesamoid bones in the Stifle Joint of Dog 1. Patella (L. The largest sesamoid 1. Base  is blunt and Little plate; Knee bone of the body; ovate in faces proximally. cap) shape and curved so as to 2. Apex  distally articulate with the patellar located and is slightly surface of the femur. 3. Articular surface 2. Fabellae Two sesamoid bones located in the heads of the gastrocnemius muscle 3. Third Associated with the Sesamoid bone tendon of the popliteus muscle. o TIBIA (Shin bone)  A long, strong bone lying on the medial part of the crus or true leg.  Proximally articulates with the femur, distally with the tarsus, and laterally with the fibula. KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 21 Proximal Extremity Shaft/Body Distal Extremity Lateral and medial condyles Caudal, medial and lateral Cochlea (Articular areas) surfaces Medial malleolus Intercondyloid eminences Medial, interosseous and cranial Cranial and caudal intercondyloid borders areas Medial and lateral intercondylar tubercles Tibial tuberosity Cranial border (Tibial crest) Popliteal notch  Proximal Extremity o Proximal Articular Surface (Lateral and Medial Condyles)  extending from the margin of the base on each side of a central elevation; the articular areas are separated by a sagittal, non-articular strip, and two intercondyloid eminences; articulates with the femoral condyles and fibrocartilage discs (medial/lateral menisci). o Intercondyloid eminences low but stout divided eminence between the medial and lateral tibial condyles. o Medial and lateral intercondylar tubercles o Cranial intercondyloid areas  the oval, depressed area cranial to the intercondyloid eminences. o Caudal intercondyloid areas  the smaller, depressed area caudal to the eminences o Popliteal notch  caudally between the condyles. o Tibial tuberosity the large quadrangular proximal cranial process where quadriceps muscles and the patellar ligaments are being attached. o Cranial border formerly the tibial crest; extending distally from the tibial tuberosity; also for muscle attachment. o Extensor groove is a smaller notch which cuts into the lateral condyle as far as the articular area. o Facies articularis fibularis on the caudolateral surface of the lateral condyle for articulation with the head of the fibula.  Body o Caudal, medial, and lateral surfaces/ medial, interosseous and cranial borders  Distal extremity o Distal articular surface or COCHLEA  two nearly, sagittal grooves receiving the ridges of the proximal trochlea of the tibial tarsal bone. o Medial malleolus  the whole medial part of the tibia with a cranial part formed by a stout pyramid-shaped process. o FIBULA (L. Pin or skewer, calf bone)  A long, thin bone bearing little weight and is situated along the lateral border of the tibia, from which it is separated by the interosseous space of the leg; much more slender and does not articulate with the femur.  Mainly for muscle attachment.  Divided into: body/shaft, lateral malleolus, or distal extremity o Facies articularis capitis fibulae small facet at the proximal head; articulates with a similar one on the caudolateral part of the lateral condyle of the tibia. o Lateral malleolus the distal end of the fibula o The HINDPAW  Tarsal bones  Metatarsal bones  Digits  Sesamoid bones o TARSUS (Hock)  Consists of seven tarsal bones. Proximal Row Central Part Distal Row Tibial tarsal (Talus, Ankle Central tarsal First tarsal bone) Second tarsal Fibular tarsal (Calcaneus, Heel Third tarsal bone) Fourth tarsal  Proximal Row Talus (L. Ankle bone, tibial tarsal)  the largest bone of the tarsus situated at the tibial (medial) side and has a o trochlea for articulation with the distal end of the tibia. o Calcaneus (L. Heel, fibular tarsal)  situated at the fibular (lateral) side, has a process, the calcaneal tuber, which projects proximally and plantarly and constitutes a lever for the muscles which extend the hock joint.  Central tarsal bone  lies on the medial part of the tarsus between the proximal and distal rows.  Proximal row o First tarsal bone  articulates with central tarsal, second tarsal, and the first metatarsal. o Second tarsal bone  the smallest of the tarsal bones. KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM  G e n e r a l V e t e r i n a r y M a c r o s c o p i c A n a t o m y : O s t e o l o g y | 22 o Third tarsal bone  nearly three times larger and two times longer than the second tarsal bone. o Fourth tarsal bone  articulates with the central (slopes upward and outward) and third (downward and inward) tarsals medially. o Metatarsus (Metatarsal bones)  First metatarsal  Metatarsal bones II, III, IV and V 1. Proximal base 2. Shaft/body 3. Head o Digits and sesamoid bones are described similarly in the thoracic limbs. BRIEF COMPARATIVE REVIEW OF THE LIMB BONES THORACIC LIMB PELVIC LIMB Scapula (girdle) Hip bone (girdle) Humerus Femur Head and neck of the humerus Head (with fovea) and neck of the femur Greater & Lesser tubercles Greater, Lesser & Third trochanters Intertubercular groove Intertrochanteric crest/Trochanteric fossa Lateral epicondylar crest Lateral (medial) supracondylar tuberosities Humeral condyles (Trochlea and Capitulum) Femoral Condyles (the trochlea is the surface for the patellar bone and not a part of the condyle) Radius Tibia Articular fovea and articular circumferences Irregular shaped proximal head with condyles Radial tuberosity Tibial tuberosity Styloid process of the radius Medial malleolus Ulna Fibula Proximal head is presented with a number of Proximal head is smoother and has one articular processes (olecranonradial notch) surface for attachment with the tibia Styloid process of the ulna Lateral malleolus Carpals Tarsals Seven carpal bones (proximal and distal rows) Seven tarsal bones (proximal and distal rows with one central part) Metacarpals Metatarsals Five metacarpal bones Five metatarsal bones, the first usually atypical Always remember the position of the base and Always remember the position of the base and the head the head Digits Digits Five digits Five digits (with the true dewclaw)  SPLANCHNIC/HETEROTOPIC SKELETON o OS Penis or BACULUM  Always present in the male dog; passes through the bulbus glandis. 1. Caudal part (BASE)  truncated and attached to the tunic of each cavernous body. 2. Cranial part (APEX)  tapers gradually and ends in cartilaginous tip attaching to corona of the glands. 3. Body  URETHRAL GROOVE, running ventrally along the base and body of the bone. o OS Clitoridis  The counterpart of the os penis in the bitches. KHAN LAMANERO JUNATAS, DVM Department of Basic Veterinary Sciences, CVM-USM