1.0: Introduction
Anatomy is a branch of biological science, which studies the physical structure, form and organisation of the body and its parts. It is closely related to Physiology, which studies the functions of the body and its parts.
Macroscopic or Gross Anatomy studies the structure and form of an organism based on observations made with the unaided eye and simple dissecting instruments (scalpel, forceps, scissors etc).
Histology or Microscopic Anatomy studies the structure and form of tissues
Embryology is a branch of Histology which studies the changes which occurs in an organism during the earlier phases of development of the embryo, when organs and tissues are formed.
Ontogeny studies the changes which occur during the entire development of the organism.
Comparative Anatomy describes and compares the structure of animals and forms the basis for their classification.
Veterinary Anatomy deals with the form and structure of the main domesticated /Farm Animals. In Anatomy three Approaches or methods of study are used: Systemic, Topographical & Applied.
Systematic approach considers the body to consist of organ systems or apparatus similar in origin and structure which are associated in the performance of certain functions.
The divisions of systemic Anatomy are:
1 Osteology
2 Syndesmology
3 Myology
4 Splanchnology
5 Angiology
6 Neurology
7 Sense organs
8 Common integument (skin)
Topographical Anatomy describes the relative positioning (location) of the various organs of the body.
Applied Anatomy refers to the use of the knowledge of systemic Anatomy in Clinical disciplines such as clinical diagnosis, Surgery, obstetrics and others.
Terminologies Used In the Study of Anatomy
Ventral surface: Surface directed towards the plane of support or ground.
Dorsal surface: Surface directed opposite the ground.
Sagittal Plane: An imaginary line which divide the body into left and right halves.
Median plane or mid sagittal plane: An imaginary line which divides the body into two equal left and right halves.
A structure or surface which is nearer to the median plane relative to another surface or structure is termed Medial or Internal.
An object or surface farther away that another from the median is termed lateral or external.
Transverse or horizontal plane: an imaginary line perpendicular to the median plane and divides body into upper/dorsal and lower /ventral parts.
Frontal plane or coronal plane: An imaginary line perpendicular to the median and transverse planes and divides body into cranial/anterior and caudal/posterior parts.
The head end of the body or organ is called cranial or anterior. In the region of the head, instead of cranial, the term rostral is used.
The tail end of the body is referred to as caudal or posterior.
Proximal: Upper part of body (part nearer to the long Axis).
Distal: Lower part of the body (part farther away from the long Axis).
Below the carpus, the caudal surface of the forelimb is referred to as being palmar. Below the tarsus, the caudal surface of the hind limb is referred to as being plantar.
Superficial: Located on the surface of an organ or structure.
Profundus (Deep): Located inside the surface of the organ or structure.
Prone: Position in which the dorsal part of the body or extremity is uppermost.
Supine: position in which the ventral aspect of the body or the plantar or palmar part of an extremity is uppermost.
There are usually projections and depressions from bones. If these projection and depressions form part of a joint, they are termed articular.
Projections and depressions outside the joint are termed non-articular. They normal serve for the attachment of muscle, tendons and ligaments.
Articular Projections
Head: Spherical articular projection e.g. head of femur.
Condyle: more or less spherical articular mass, e.g. trochlea on distal part of femur, on which the patella slides.
Facet: Relatively flat articular surface as found between adjacent carpal bones.
Non-Articular Projections.
Process: general term for a bony projection such as the spinous process.
Tuber: Relatively large non-articular projection, such as the lateral tuberosity on the humerus.
Tubercle: Smaller projection
Spine: pointed projection such as the spine at the proximal end of the Tibia or a ridge such as the spine of the scapula.
Crest: Sharp ridge
Neck: Cylindrical part of bone to which a head is attached.
Line: small ridge or mark on a bone often caused by the pull of a muscle.
Articular Depressions.
Glenoid Cavity: Shallow articular depression such as on the articular surface of the scapula.
Cotyloid Cavity: deep articular depression such the acetxabulum of the pelvis.
Notch: articular indentation such as the semi-lunar notch of the ulna.
Non. Articular Depressions
Fossa: Large non-articular dépression
Fovea: small non-articular depression such as the fovea capitis on the head of the femur.
Foramen: circumscribed hole in a bone.
e.g. Foramen magnum, foramen obturator
Canal: tunnel through one or more bones such as the vertebral canal.
Structure of Animal Tissues and Cells
The cell is the basic unit of all living organisms. A typical cell consists of the cytoplasm, the nucleus and the cell membrane.
In multicellular organisms, certain cells perform specific functions. Such cells are grouped together to form tissues. Tissues are associated in functional groups called organs. A number of organs involved in a common enterprise make up a system. For example, the stomach, liver, pancreas and intestines are all organs making up the digestive system.
There are four main types of tissues in the body: epithelial, connective, muscle and nervous Epithelial tissues cover the surface of the body, line body cavities and form the active parts of glands.
Connective tissues support and bind other tissues together and from which in the case of bone marrow, the formed elements of blood are derived.
Muscle tissues contract and effect movements.
Nervous tissues conduct impulses from one part of the body to another.
Classification of Tissues
Epithelial tissues
Epithelial tissues are classified as simple (single layered), and stratified (many layered).
Simple epithelium includes squamous (plate-like) cells, cuboidal cells, columnar (cylindrical shaped) cells, and pseudo-stratified columnar cells.
Simple squamous epithelium consists of thin plate-like cells. They are found where a smooth surface is required to reduce friction. E.g. mucosa of visceral organs and lining of body cavities and blood vessels.
Cuboidal epithelial cells line some glands and some passageways in the kidney.
Columnar epithelial cells are cylindrical in shape and are arranged like the cells in a honey comb. Some columnar cells have whip-like projections called cilia, extending form the free extremity. The cells lining the trachea are ciliated and help trap any foreign material towards the mouth where it can be coughed out or swallowed.
Pseudo-columnar epithelium is made of columnar cells of varying length, giving it the appearance of more than one layer. E.g. cells in the upper respiratory tract.
Stratified epithelium consists of more than one layer of epithelial cells. They include stratified squamous, stratified columnar and transitional.
Squamous epithelium lines the epidermis, and the lining of the first part of the digestive tract as far as the stomach. In ruminants it lines the fore stomach.
Stratified columnar epithelium consists of more than a layer of columnar cells. It lines part of the pharynx and salivary glands.
Transitional epithelium lines the ureters and urinary bladder. It is able to pile up many cells thick when the bladder is empty, and stretches out to a single layer, when the bladder is full.
Glandular epithelium is either cuboidal or columnar. The cells may be arranged as single goblet cell, or consist of aggregations of many cells.
Connective tissues include: yellow elastic tissue, collagenous (white fibrous) tissue, reticular tissue (net-like), adipose (fat) tissue, cartilage (gristle) and bone.
In loose connective tissues the cells are widely dispersed in semi-fluid matrix with scattered fibres.e.g areolar tissue.
In fibrous connective tissues there are more fibres than cells. White fibrous tissue contains more collagen fibres. These accounts for its strength.
Yellow fibrous tissue contains more elastin fibres.
Reticular connective tissue made up the framework of lymphatic tissue such as spleen, and bone marrow.
Adipose tissue (sometimes called fat) form when connective tissue cells store fat as inclusions within their cytoplasm.
Dentine (ivory) is similar to bone but harder (contain higher mineral content).
Cartilage and bone are known as skeletal tissue.
Cartilage is a special type of connective tissue commonly called gristle. It is firmer than fibrous tissue but not as hard as bone. It consists of cells embedded in a matrix of organic substance called chondrin.
There are three types of cartilages: hyaline, yellow elastic and fibrous.
Hyaline cartilage is the glass-like covering of bones within joints. It enables one bone to easily glide over the other.
Yellow elastic cartilage consists of a mixture of cartilaginous substance and elastic fibres. It forms the basis of the external ear and epiglottis.
Fibrous cartilage is made up of a mixture of cartilage and collagenous fibres. It is found at the intervertebral discs of adjacent vertebrae.
Bone differs from cartilage in that the bulk of its matrix consists of inorganic salts mainly calcium phosphate (2/3) and 1/3 organic matter as in cartilage.
Bone is a special type of connective tissue formed by osteoblasts. Osteoblasts produce osteoid tissue that latter calcifies to form bone. The bone may be arranged in the form of spicules and flat plates, forming a sponge-like network called cancellous or spongy bone. Cancellous bone is found in the extremities of long bones, or between two layers of compact bone.
Alternatively bone may be hard bone in the form of laminated cylinders (Haversian system) closely packed together to form compact bone. Compact bone is found in the shaft (body) of long bones.
Blood is a connective tissue derived from bone marrow.
There are three types of muscle tissue: Striated voluntary (skeletal) muscle, smooth muscle (involuntary) and cardiac (involuntary striated) muscle.
Nervous tissue consists of neurons (nerve cells) made up of a nerve cell body and two or more nerve processes (fibres).
2.0: Osteology
Osteology is the study of the skeletal system of the body. The skeleton is a framework of hard structures which support and protect the softer tissues of body.
In lower animals or invertebrates the skeleton is said to be an exoskeleton. E.g. cuticle of insects. In mammals the skeleton is an Endoskeleton, since it is embedded in the softer tissues (skin, fascia, muscles).
The skeleton consists of a framework of bones of the body joined in their natural positions by ligaments and joints.
Bone is made up of fibrous tissue, phosphate and carbonate of lime. The bones of young animal contain more than 60% fibrous tissue, while that of adult animal contains less than 60% fibrous tissue. This explains the brittleness of the bone of young animals and the toughness or hardness of the bones of adult animals.
According to their structure and functions, bones are divided into the following classes:
1 Long bone - ossa longa.
Long bones are usually greater in length than breath. They usually consist of a cylindrical shaft (diaphysis) and two extremities called epiphysis with a metaphysis between each epiphysis and the diaphysis. E.g. humerus, radius, ulna, phalanges, metacarpals, femur, tibia, fibula, metatarsals.
2 Short bones - ossa brevia
Short bones are somewhat cuboids or approximately equal in length, breath and thickness. E.g. carpus , tarsus, sesamoid.
3 Flat bone - ossa plana
Flat bones are expanded in two directions. E. g. Scapula and many bones of the skull.
4 Irregular bones
These are bones with irregular shape. E.g. Vertebrae and some unpaired bones of the skull.
5 Pneumatic bone
This bone contain air spaces or sinuses that communicate with the outside. E.g. Para nasal sinuses in frontal and maxillary bones.
Structure of Bones.
Chemically dried bone consists of organic matter (bone collagen or ossein) & inorganic matter (bone ash, mainly calcium phosphate) in the ratio of approximately 1:2.
Organic matter gives toughness and elasticity while inorganic matter gives hardness.
Externally bone is covered by the periosteum ,which consists of an outer protective fibrous layer and an inner cellular osteogenic layer.
The endosteum lines the medullary cavity and the haversian canals.
Bone consists of an external shell of dense compact substance and an inner loosely arranged spongy substance.
Compact bone is made of bone matrix deposited in layers called lamellae arranged concentrically around a central haversian canal. Within the interstitial substance of bones are cavities called lacunae filled with osteocytes (bone cells) .Slender tubular passages called canaliculi radiate from the lacunae. They are essential to the nutrition of bone cells. A system of vascular channels called the Haversian system exists in compact bone. Compact substance forms the bulk of long bones.
Spongy bone consists of delicate bony plates and spicules, arranged randomly with a lot of spaces between them.. In these spaces are marrow spaces. There are Red and Yellow Bone Marrow in adult animals. Red bone marrow is precursors to Blood cells .In yellow marrow part of the marrow is replaced by adipose tissue.
Spongy substance forms the bulk of short bones and the extremities of long bones.
Development and Growth of Bone
Primitive embryonic skeleton consists of cartilage and fibrous tissue.
The Process of bone formation is termed ossification or osteogenesis. Bone forming cells are known as osteoblasts.
Bones formed from fibrous tissue membranes are said to be of intramembraneous origin.e.g bones of the roof and sides of the cranium and most bones of the face.
Most bones of the skeleton are formed from cartilage (endochrondral origin).
1The skeleton is divided into 3 parts.
6 Axial skeleton - vertebral column, rigs with their cartilages, sternum and skull.
7 Appendicular skeleton- thoracic (fore limb) and pelvic (hind limb) appendage.
8 Splanchnic (visceral) skeleton - Bones embedded in the substance of organs. E.g. Hyoid, bone in the heart of ox, snout or os rostrale in the pig and os penis in the dog.
Axial Skeleton
Vertebral column.
Vertebral column is formed by bones called vertebrae. Vertebrae are unpaired, irregular bones which extend from the skull to the end of the tail.
Some vertebrae have become joined together (fused) to form a single bone. Such a vertebra is termed fixed or false. Eg. Os sacrum.
The other single vertebrae are movable or true vertebrae.
According to their location in the part of the body, the vertebral column is subdivided into the following region:
1 Cervical ( C ) or neck vertebrae
2 Dorsal or thoracic vertebrae (T)
3 Lumbar (L) vertebrae - in the region of the loin
4 Sacral (S) vertebrae - in the crump region
5 Coccygeal (CY) or tail vertebrae
Vertebral formula expresses the total number and type of vertebrae in a given animal. For example, in a horse, it may be expressed as C7 T18 L6 S5 Cy 15 - 21.
Vertebral Formula for Different Animal Species
NO. OF VERTEBRAE SPECIES
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C
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T
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L
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S
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CY
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Horse Cattle Deer Sheep Pig Dog
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7 7 7 7 7 7
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18 13 13 13 14 - 15 13
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6 6 6 - 7 6 - 7 6 - 7 7
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5 5 4 4 4 3
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15 - 21 18 - 20 10 16 - 18 20 - 23 20 - 23
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Structure Of A Typical Vertebra.
A typical vertebra consists of a body, arch and processes.
The body is a cylindrical mass on which the other parts are constructed. It has two ends (cranial and caudal extremities). The dorsal surface is flattened and forms part of the vertebral canal.
The Arch is constructed on the dorsal aspect of the body. It consists of two lateral sides, each of which is made up of a ventral pedicle and a dorsal lamina. The pedicle forms the lateral part of the arch and is cut into cranially and caudally by vertebral notches (incisura vetebralis cranialis, at caudalis). The notches of two adjacent vertebrae form intervertebral foramina for the passage of spinal nerves and vessels. The lamina is plates, which complete the arch dorsally, uniting with each other medially at the root of the spinous process.
The body and arch form a bony ring enclosing the vertebral foramen.
The processes present in a typical vertebra include articular, spinous, transverse, and accessory processes.
Articular processes are prominent in cervical vertebrae.
The spinous process or spine is single and project dorsally from the middle of the arch (lamina)
Transverse processes are paired and usually project laterally from the sides of the arch or from the junction between body and arch.
Accessory processes (e.g. mamillary processes) when present are situated between the transverse and caudal articular processes.
Some vertebrae also have a ventral crest, ventral tubercle and haemal arch. The bodies of vertebrae are joined by fibro-cartilaginous intervertebral discs.
Characteristics of Vertebrae
Cervical vertebrae:
They are 7 in number.
Atlas----- 1st t
It has the form of a strong ring. It consists of two lateral masses (wings) or transverse processes connected by dorsal and lateral arches. On the cranial margin of the dorsal arch are alar foramina. The body and spinous process are absent. It has two oval shaped cranial articular processes for articulation with the two occipital condyles. The caudal processes are saddle shaped and articulate with the Dens of the Axis.
Axis, Epistropheus----- 2nd
It is a pivot around which the atlas rotates. The cranial extremity of the body presents centrally the Dens or Odontoid process. On either side of the dens are modified saddle shaped articular processes. The transverse process is small and single. The spinous process is large and strong.
Typical cervical vertebrae-------3---5th
Their bodies are relatively longer than the other cervical vertebrae. Articular processes project from the borders of the arch. The cranial extremity has an oval articular surface, which is wider dorsally than ventrally. The caudal extremity has a nearly cotylenoid cavity. The transverse processes are large and plate like. The spinous process has the form of a low crest.
6th cervical vertebra.
The spinous process is rudimentary compared to the 7 the cervical vertebra. The transverse processes have 3 branches: dorsal, medial and ventral.
7th cervical vertebra
Caudally it has costal facets (fovea costalis caudalis) on either side for articulation with part of the head of the 1 st rib. The spinous process is long (about 3 cm). The transverse process is undivided and devoid of a transverse foramen, except in man and pig.
Thoracic Vertebrae.
Thoracic vertebrae. in general have long and narrow spinous processes directed dorsad and caudad. The transverse processes are short and thick and presents on its ventral aspect a large concave facet for articulation with the tubercle of the rib.
Thoracic vertebrae have cranial and caudal costal facets on the dorsal side of each side for articulating with the head of adjacent ribs. An exception is the last thoracic vertebra which lacks the caudal pair of facets.
Lumbar Vertebrae
Lumbar vertebrae in general have the following characteristics:
1 Elongated transverse which project laterally
2 Short and broad spinous processes
3 Mamillary processes located either fused with the cranial articular processes or on the transverse processes
The last lumbar vertebra has on its caudal extremity modified articular surfaces with the wings of the sacrum.
Sacral Vertebrae or Sacrum.
The sacrum is formed by the fusion of the sacral vertebrae usually 5 in number.
Caudal Vertebrae.
The first three Caudal Vertebrae have short and broad spinous processes. Their transverse processes have relatively large plates. The rest of the caudal vertebrae consist of bodies only.
Ribs - Costae
Ribs are long curved bones, which form the skeleton of the lateral thorax. They are arranged serially in pairs, corresponding in number to thoracic vertebrae.
A typical rib consists of a body and two extremities (ends).
The vertebral extremity consists of the head, neck and tubercle.
The head is the actual end of the rib. It contains cranial and caudal convex facets (facies articularis capitis costae) for articulation with the bodies of adjacent thoracic vertebrae. These surfaces are separated by a groove.
The neck joins the head to the body. The tubercle projects caudally at the junction of the neck and body. It has a facet for articulation with the transverse process of the corresponding thoracic vertebrae, with which the head articulates.
The ventral extremity is slightly enlarged and roughened at the junction with costal cartilage.
Sternal ribs are joined to the sternum by costal cartilage.
On the other hand, asternal ribs are not connected to the sternum. Their costal cartilages overlap and attach to each other by elastic tissue, forming the costal arch.
Sometimes the last one or two ribs are not connected to the other ribs and are therefore referred to as floating ribs.
Costal cartilages are bars of hyaline cartilage, which join the ribs to the sternum. Or breast bone.
The sternum is a median segmental bone which completes the skeleton of the thorax ventrally. It consists of a variable number of segments or sternebrae, related to the number of Sternal ribs in an animal species. The number of stern brae in animals is as follows:
Pig and Sheep - six (6) sternebrae
Cow and Goat - seven (7) sternebrae
Horse and Dog - eight (8) sternebrae.
The 1st segment or cranial extremity of the sternum is called the manubrium sterni or presternum.
The body of the sternum or mesosternum presents at the junction of the segments, concave facets (incisura costales) for articulation with the cartilages of Sternal ribs.
The caudal extremity or last sternebra (metasternum) presents the xiphoid Process.
Thorax
The skeleton of the thorax consists of thoracic vertebrae dorsally, ribs with their costal cartilages laterally and the sternum ventrally.
The Skull
The skull protects the brain and the organs of special senses (ear, eye). Most of the bones of the skull are flat bones, separated from each other by immovable joints called sutures. These joints can be felt during early life, but are fused in adulthood.
The bones of the skull are divided into bones of the cranium and bones of the face. The cranium encloses the brain and its membranes.
The bones of the cranium consist of the following bones;
1 Single bones - occipital bone
- Sphenoid bone
- Ethmoid bone
1 interparietal bone
2 Paired bones - parietal bone
- Frontal bone
- temporal bone
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-
The bones of the face include the following:
3 Single - vomer
- Mandible or lower jaw bone
- Hyoid
4 Paired bones
Maxilla, incisive (pre-maxilla), palatine, pterygoid, nasal, lachrymal, zygomaticus dorsal and ventral conchea.
The pterygoid bone is visible externally as the hamulus of the pterygoid (a projection just behind the last molar tooth).
The orbit is a bony socket protecting the eye. It is formed by portions of the frontal, zygomaticus, and lachrymal bones.
Mandible - lower jaw bone.
The mandible is the largest bone of the face. At birth it consists of two halves which fuse after 2-3 months of age. In bovine, the two halves don’t fuse completely, even in advanced age, and form a symphysis.
The mandible consists of a body and two vertical rami. The body is the thick horizontal part, which presents teeth. It consists of an incisive and a molar part. At the junction between the molar and incisive part of the body, is the mental foramen. The mental foramen is an external opening of the mandibular canal. The ramus is the vertical part of the mandible and serves for the attachment of powerful jaw mussels.
The occipital bone consists of squamous, lateral and basilar parts.
The squamous part is located dorsally to the lateral part and is shaped like a quadrilateral. Its external surface is crossed by a prominent ridge, the nuchal crest. The middle part of the nuchal crest forms the highest point of the skull.
The lateral parts bear the occipital condyles for articulation with the atlas. Lateral to the condyles are the jugular (Para mastoid) processes for the attachment of muscles.
The basilar part is located ventrally. Rostrally it is attached to the sphenoid bone.
The cranium or cranial cavity encloses the brain with its membranes and vessels. It is ovoid in shape. It dorsal wall or roof is formed by the squamous part of the occipital; inter parietal, parietal and frontal bones.
Its lateral wall is formed chiefly by the temporal, and frontal bones and the wings of the presphenoid.
Its ventral wall or floor is formed by 3 fossae: rostral cranial fossa, middle cranial fossa and caudal cranial foosa. The rostral cranial fossa supports the frontal and olfactory parts of the cerebrum and is formed mainly by the presphenoid bone.
The middle cranial fossa extends caudad to the spheno - occipital (basisphenoid). The hypophysis, piriform lobe of the cerebrum and some nerves are located in this region.
The caudal cranial fossa corresponds to the basilar part of the occipital bone. It contains the medulla oblongata, pons and cerebellum. The rostral or nasal wall is formed by the cribiform plate of the ethmoid, which separates the cranium from the nasal cavity.
Para nasal sinuses are cavities found in the interior of some bones of the skull. They all drain directly or indirectly into the nasal cavity. One group of sinuses drain into the middle nasal meatus and the other group into the caudal dorsal part of the nasal cavity.
Sinuses are found in the following bones. Frontal, maxillary, palatine, lachrymal, sphenoid and conchae.
The nasal cavity extends through the dorsal part of the face. It is divided into right and left halves by a median nasal septum. Its lateral walls are formed by the maxilla,Incisive, perpendicular part of the palatine and nasal conchae, and ethmoid bones in part.
The dorsal wall or roof is formed y the frontal and nasal bones. The ventral wall or floor is formed by the palatine processes of the incisive and maxilla, and the horizontal parts of the palatine bones.
The osseous nasal septum is formed by the perpendicular plate of the ethmoid caudally and the vomer ventrally.
The nasal conchae divide each half of the nasal cavities into three meatuses - Dorsal nasal meatus, middle nasal meatus and ventral nasal meatus. In addition a common nasal meatus lies in the space between the nasal septum and the medial surface of the dorsal and ventral nasal conchae.
The caudal extremity or fundus is separated from the cranial cavity by the cribiform plate of the ethmoid, and is largely occupied by the ethmoidal labyrinth.
Appendicular Skeleton
The appendicular skeleton includes the bones of the thoracic appendage or fore limb and the pelvic appendage or hind limb. A comparison of the composition of the bones of both limbs is shown in this presentation.
Man has a clavicle (collar bone), while poultry have coracoid as a separate bone. In domestic animals and man, the coracoid has been reduced to the coracoid process, which protrudes medially from the scapula.
The thoracic appendage is joined to the axial skeleton through a false joint (group of muscles). On the other hand, the pelvic appendage is joined to the axial skeleton through the sacro - iliac joint.
Comparison of Bones of the Appendicular Skeleton
THORACIC (PECTORAL) LIMB
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PELVIC OR HIND LIMB
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Pectoral girdle Scapula, clavicle, coracoid Humerus - arm Radius ulna - fore arm Carpus - Knee Meta carpus - Cannon phalanges- digits sesamoids
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Pelvic girdle - pelvis Ilium, pubis, ischium Femur - thigh Tibia and fibula - leg Tarsus - Hock Metatarsus - cannon Phalanges - digit sesamoids
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Thoracic Appendage
In the text, the general structure of bones will be described. This will be followed by a brief comparative anatomy in respect of the different species of animals whenever possible.
Scapula - Shoulder Blade
The scapula is approximately triangular in outline and is attached to the vertebral column through muscle fibres (false joint). Its distal portion however forms a joint with the humerus. The scapula has a lateral surface and a medial (deep or costal) surface. The lateral surface has a ridge called spine which divides the scapula into two depressions.
Supraspinous fossa (cranial) - in front of spine
Infraspinous fossa (caudal) - behind the spine
On the costal or medial surface is a depression called sub scapular fossa for the attachment of the sub scapular muscle.
In bovine the spine is prominent and has a projection towards the distal end called the acromion.
Distally the body of the scapula continues as the neck of the scapula and ends with the glenoid cavity. The glenoid cavity is an articular depression for articulating with the head of the humerus.
The Glenoid cavity bears a distinct prominence, supra glenoid tubercle (located cranially) for the attachment of the biceps brachi. Medial to the supraglenoid tubercle is the coracoid process (remnant of coracoid bone) for the attachment of the coracobrachial muscle.
Scapula of horse;
Acromion is absent
Scapula of a bovine
Prominent acromion is present
Scapula of ovine
Spine is less sinous, glenoid cavity is relatively longer.
Scapula of pig;
Scapula has a large tuberosity close to the caudal angle. Acromion is rudimentary.
Scapula of dog;
Acromion is short and blunt; spine divides the lateral surface into nearly two equal fossa (supraspinous & Infraspinous).
In all other animals the Infraspinous fossa is usually larger than supraspinous fossa.
Humerus
The humerus is a long bone, which proximally articulates with scapula and distally with the radius and ulna. It consists of two extremities and a body or shaft. The proximal end consists of the head, neck, two tuberosities (lateral and medial) or two Tubercles (greater and lesser tubercle), and an inter tuberal groove.
The distal end consists of the medial and lateral epicondyles, the olecranon (located caudally) and the radial (located cranially) fossae. It also has an oblique surface for articulation with the radius and ulna. This is made up of the trochlea (medial condyle) and capitulum (lateral condyle).
Just proximal to the middle of the median surface is the teres major tuberosity. The deltoid tuberosity is located on the cranial surface. Proximal to this tuberosity is a small prominence, the teres minor tuberosity.
Humerus of bovine/ovine
Lateral tuberosity is very large and rises about 3cm above the level of the head.
Humerus of the horse
Lateral tuberosity is divided in two by a bicipital groove.
Humerus of pig
Lateral tuberosity almost converts bicipital groove into a foramen. The teres major tuberosity is absent and the olecranon fossa is deep.
Humerus of dog
Deltoid tuberosity has the form of a ridge and bears a tubercle at its proximal end.
The radial and olecranon fossae communicate through a large supratrochlear foramen. The lateral tuberosity is undivided.
Radius and Ulna
Of the two bones, the radius is the better developed in most domestic animals. It extends from the elbow to the carpus. The radius consists of a body or shaft and two extremities. At the proximal extremity are the humerus articular surface and radial tuberosity (located medially). The distal end presents carpal articular surfaces made up of the medial, intermediate and lateral facets. The medial facet articulates with the radial carpal bone, the intermediate facet articulates with the intermediate carpal bone, and the lateral facet articulates distally with the ulnar carpal and caudally with the accessory carpal bones. The cranial surface has grooves separated by ridges for the attachment of tendons. The caudal surface has a transverse crest for the attachment of ligaments.
The ulna in most animals is a reduced bone, situated caudal to the radius. It is partly fused with the radius in adult animals. The ulna consists of a proximal extremity or olecranon, and body (shaft) which tapers to a point distally. The olecranon is the main part of the ulna. On its cranial border is the anconedal process, over hanging the trochlear notch. An interosseus space exists between the point of fusion of the ulna and radius.
In the horse, the ulna ends distally, fused with the radius at a distance approximately 2/3 the total length of the radius. A small interosseus process is present.
In the bovine, radius and ulna is fused at both ends of the radius (proximal and distal). Two inter osseus spaces are present at both ends of the bones. At the distal end, the ulna together with the radius forms a styloid process.
In the ovine, the arrangement of the ulna and radius is similar to that in the bovine. However the ulna is not necessarily fused to the radius and is more slender.
In the pig, the radius is short and narrow. The ulna is more massive than the radius. The interosseus space is located in the proximal third.
In the dog, the ulna is longer than the radius. The two bones are not fused but articulate with each other at the proximal and distal ends. A large interosseus space exists between their bodies. There is a styloid process at the distal end of the ulna.
Carpal Bones
The carpal bones are a group of short bones, usually eight in numbers arranged in two transverse rows - proximal and distal. The names relative positions of the bones are indicated as follows:
Proximal Row
Radial Intermediate Ulna Accessory
Distal Row
MEDIAL First Second Third Fourth LATERAL
In the horse, the carpal bones consist of 7 or 8 bones arranged in two rows. In bovine, the carpal bones are 6, 4, in the proximal row and 2 in the distal row.
In ovine, the arrangement is the same size as in bovine, but of smaller dimensions.
In the dog, there are 7 bones, 3 in the proximal row and 4 in the distal row.
In the pig there are 8 carpal bones.
Metacarpal Bones or Metacarpus
The metacarpus consists of 5 metacarpal bones (I - v) for each digit. They are long bones and designated numerically from the radial to the ulnar side (that is from medial to lateral). Metacarpus has a body and two extremities. The proximal extremity has undulating articular surfaces for the distal rows of carpal bones. The distal extremity has articular surfaces for the proximal phalanx and proximal sesamoid. This arrangement is typical of dogs. In the dog the 1st Meta carpal is the smallest bone, while the 2nd and 5th are also reduced in size.
Animals are classified as odd -toe or ungulates and even -toe animals depending on the structure of the metacarpal bones.
In ungulates such as the horse the 1st and 5th metacarpals are absent. The 3rd metacarpal bone is fully developed and carries the single digit while the 2nd and 4th are much reduced. They are referred to as small metacarpals or ‘splint’ bones. This type of arrangement of metacarpal bones and digits is referred to as perisodactyl form.
To the artiodactyls or even -toe animals belong the following:
5 Ruminants----cattle, sheep, goats
6 Pigs and their family ---hog ,warthog
7 Camels and their related families
In artiodactyls (bovine, sheep, pig), the 3rd and 4th metacarpal bones are the chief metacarpals and bear the well - developed digits. They are fused in cattle and sheep. The others are either reduced or absent. In the pig, the 1st is absent, while the 2nd and 5th are reduced and carry the accessory digits.
Digits
The digits are usually 5 in number. The dog has the full number. In cattle and pigs, the 3rd and 4th are well developed and support the weight, while the 2nd and 5th are reduced. The horse has one digit. Each digit consists of 3 phalanges and the sesamoid bones (proximal and distal). The phalanges are called 1st or proximal phalanx, 2nd or middle phalanx, and 3rd or distal phalanx respectively. The distal phalanx is enclosed by the hoof.
Sesamoid bones are developed along the course of tendons or in joint capsules at points where there is increased pressure.
In the horse, there is one digit with three phalanges and two sesamoid bones (1 proximal, 1 distal). The two proximal sesamoid bones are situated palmar to the distal end of the large metacarpal bone and is attached to the proximal phalanx by ligaments. The distal sesamoid is situated palmar to the junction between the middle and distal phalanx.
In bovine 2 digits are attached to the 2 large metacarpal bones with 4 proximal sesamoids and 2 distal sesamoids.
In ovine, the arrangement of digits is similar to that of the bovine, except that the accessory digits usually have no phalanges.
In the pig, each chief digit has 3 phalanges and 3 sesamoids (2 proximal, 1 distal). The phalanges of accessory digits are smaller in size and don’t reach the ground ordinarily.
In the dog, the 5 digits have 3 phalanges each, with the exception of the 1st which has 2 phalanges. Nine sesamoids are present. They are all proximal sesamoids. Only the 1st digit has 1 proximal sesamoid. The distal sesamoids are cartilaginous.
Pelvic Appendage - Hind Limb
Pelvic girdle (bony pelvis)
The pelvic girdle includes the pelvis (ossa coxarum), sacrum and the first three or more caudal vertebrae. The pelvis is joined to the axial skeleton by the right and left sacro - iliac articulations.
Pelvis
The pelvis consists of 3 bones (ilium, pubis and ischium) fused together as one bone at the pelvic symphysis.
Ilium
It is the largest and most dorsal of the 3 bones. It is irregularly triangular in shape. It has a median angle called the tuber sacrale (near to the sacro-iliac joint) and a lateral angle called tuber coxae. The tuber sacrale is the highest point of the skeleton. The broad, flat portion of the bone between the tuber sacrale and tuber coxae is called the wing of the ilium. It continues downward as the body of the ilium.
Pubis.
The body of the ilium continues downward into the pubis. It is the smallest of the 3 bones and forms the cranial floor of the pelvis. The pubis consists of a body, and two branches (cranial or ace tabular and caudal or symphyseal).
Together with the ischium the pubis forms the obturator foramen. The three bones together form the acetabulum for articulation with the head of the femur.
Ischium
Ischium forms the caudal part of the floor of the bong pelvis. It consists of a body, ramus, tuber and tabula.
The body lies lateral to the obturator foramen. The tabula is the irregularly quadrilateral portion lying caudal to the body. The caudolateral angle of the ischium bears the ischiatic tuberosity for the attachment of muscles (biceps femoris and semi-tendinous).
Pelvic Cavity
The bony framework of this cavity is formed by bones of the pelvic girdle. The dorsal wall or roof is formed by the sacrum and the first three caudal vertebrae. The ventral wall or floor is formed by the pubic and ischial bones.
The lateral walls are formed by the ilia and the acetabular part of the ischia.
The cranial aperture or inlet of the pelvis is bounded by the terminal line or brim. The caudal aperture or outlet of the pelvis is bounded dorsally by the 3rd caudal vertebra and ventrally by the ischiatic arch.
Femur
The femur has a cylindrical body (shaft) which is larger proximally than distally. The proximal extremity presents the head, neck and greater trochanter. The head is located medially and articulates with the acetabulum. It is cut into medially by a deep notch (fovea capititis femoris) to which both the accessory ligament and ligament to the head of the femur are attached. Below the neck on the medial border of the femur is the lesser trochanter. Just below this lesser trochanter can be found the nutrient foramen. The medial supracondyloid tuberosity is situated further distally after the nutrient foramen.
The greater trochanter is situated laterally. Its cranial part is situated opposite the head and rises a little proximal to the head. Its caudal part is separated from the cranial part by a notch (incisura trochanterica). Its caudal border continues distally as the trochanteric crest. Another prominence, third trochanter is located below the trochanteric crest as in the horse.
In bovine, the lesser trochanter has the shape of a rough tuberosity and is connected with the greater trochanter through the inter- trochanteric crest. The third trochanter is absent.
In the pig, the head of the femur and greater trochanter are almost at the same height. The third trochanter is absent, and the lesser and greater trochanter are connected by the inter trochanteric crest.
In the bog, the third trochanter is small, and the supracondyloid fossa is absent.
The distal extremity consists of the trochlea cranially and two condyle (medial and lateral) caudally. The two condyle are separated by the deep intercondyloid fossa and articulate with corresponding (lateral and medial) condyle of the tibia. The trochlea consists of two ridges separated by a ridge and forms an extensive articular surface for the patella.
On the medial surface of the distal extremity is the medial epicondyle, a non-articular projection for the attachment of muscles and ligament. The lateral epicondyle is found on the lateral surface of the distal extremity.
The patella is a large sesamoid bone, which articulates with trochlea of the femur. It has a base, an apex, medial and lateral borders and two surfaces.
Tibia
Tibia is a long bone which articulates proximally with the femur, distally with the tarsus and laterally with the fibula. At its proximal end, it has two eminences, lateral and medial condyle for articulation with their corresponding condyle of the femur. In between these condyle is the intercondylar eminence.
At the distal end there is an articular surface adapted to the shape of the trochlea of the talus. It consists of two grooves separated by a ridge. The ridge and grooves are bounded on either side by the lateral and medial malleoli respectively; the malleoli serve for the attachment of ligaments and tendons.
Fibula
Fibula is a bone situated on the lateral border of the tibia. It is separated from the tibia by the interosseus space of the leg. The head or proximal end of the fibula articulates with the lateral condyle of the tibia.
In the horse, the fibula is a reduced bone, with its distal end terminating at a point one half to two thirds of the way down the lateral border of the tibia. The distal end is fused with the tibia to form the lateral malleolus.
In bovine and ovine, the distal end of the fibula remains separate and forms the lateral malleolus. In the pig, the fibula and tibia remain as separate bones from the proximal to distal end. Both bones are separated by a large interosseus space.
In the dog, the proximal part of the fibula and tibia are separated by on interosseus space. However at the distal end both bones are closely attached to each other.
Tarsal bones - hock.
The tarsal bones or tarsus consists of a number of short bones, usually 6 - 7 arranged in two rows.
Their mode of arranged is shown as follows:
Proximal Row
Medial Tibial Fibula Central Lateral
Tarsal Tarsal Tarsal
Bone Bone Bone
TALUS CALCANEUS CENTRAL
Distal Row
1st 2nd 3rd 4th
The talus or Tibial tarsal bone articulates with the distal end of the tibia. The calcaneus or fibula tarsal bone is largest of the hock bones. It is enlargened at its proximal end to form the calcaneal tuber or point of the hock. The Achilles tendon takes its origin from this point (calcaneus tuber).
In the horse, the tarsus consists of 6 short bones, sometimes 7.
In the bovine or ovine, the tarsus consists of 5 bones. The central tarsal and 4th tarsal bones as well as the 2nd and 3rd tarsal bones are fused.
In the pig and dog, the tarsus consists of 7 bones.
Meta Tarsal Bones or Metatarsus
The metatarsal bones resemble the metacarpal bones. However the 3rd metatarsal bone is about 1/6 longer than the corresponding metacarpal. The 2nd and 4th (small) metatarsals are a little longer and more massive than the corresponding metacarpals. At the proximal end, the large metatarsals have a large central non-articular depression.
Digits
The digits of the pelvic limb resemble those of the thoracic limb. The axis of the phalanges of the pelvic limb forms with the grounded plane an angle which is 50 degrees greater than that of the thoracic limb.
The proximal phalanx is a little shorter, wider proximally and narrower distally. The middle phalanx is narrower and slightly longer.
The distal phalanx is narrower. The proximal sesamoids are a little smaller, except in thickness.
Functions of Bones
8 Bone provides protection for the more delicate inner structures. For example the cranium protects the brain, while the vertebral column protects the spinal cord.
9 Bones give form and rigidity to the body. The skeleton forms the basis for the external structure and appearance of most animals.
10 Long bones act as levers and help on the support and locomotion of the body. Activities such as locomotion, defense and offense depend on the contraction and relaxation of muscles attached to these levers.
11 Bones are a principal store of minerals, especially calcium and phosphorus in the body.
12 Blood and its formed elements are formed from bone marrow found in the cavity of long bones and within the spongy substance of all bones.
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