VAN211-MODULE-3-AXIAL-SKELETON.pdf
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VAN211 MODULE 3 - AXIAL SKELETON MODULE 3. AXIAL SKELETON OUTLINE Composition of the Skeleton Skeleton of the head Skull LEARNING OUTCOMES To know the components of the skeleton; To be familiar with the bones composin...
VAN211 MODULE 3 - AXIAL SKELETON MODULE 3. AXIAL SKELETON OUTLINE Composition of the Skeleton Skeleton of the head Skull LEARNING OUTCOMES To know the components of the skeleton; To be familiar with the bones composing the axial skeleton; and To identify the parts of each bone composing the axial skeleton. A. COMPOSITION OF THE SKELETON SKELETAL COMPOSITION Bones Ligaments Tendons Cartilage BONES Hard, dense connective tissues Structural support, form & rigidity, movements Mineral storage, energy storage and haematopoiesis No. bones: adult humans 206 bones; mouse 225; dogs 291-321 TENDONS Tissues that connect muscle to bone Consist of tightly packed bundles of the protein collagen arranged in parallel Act to focus a muscle's effort on a physically small portion of bone RHD/CTU-CVM BARILI CAMPUS 21 VAN211 MODULE 3 - AXIAL SKELETON LIGAMENTS A short band of tough, flexible fibrous connective tissue Strongest tissue that connect bones or cartilages or holds together a joint Similar in composition to tendons but no muscles are involved CARTILAGE Firm, whitish, flexible connective tissue found in various forms Absorbs shock More widespread in young skeleton but most are replaced by adult bones Located in joints, between ribs, nasal passages TYPES OF CARTILAGE Hyaline cartilage The most common, weakest type Precursor of bone Located in the ribs, nose, larynx, trachea Fibrocartilage Located in intervertebral discs, joints, ligaments Elastic cartilage Located in external ear, epiglottis, and larynx PARTS OF THE AXIAL SKELETON Skull Vertebral column Sternum Hyoid bones Ribs RHD/CTU-CVM BARILI CAMPUS 22 VAN211 MODULE 3 - AXIAL SKELETON B. CLASSIFICATION OF DOG HEAD CLASSES OF DOG HEAD Dolichocephalic means “long, narrow-headed” Mesaticephalic means “a head of medium proportions” Brachycephalic means “short, wide-headed” DOLICHOCEPHALIC DOG BREEDS RHD/CTU-CVM BARILI CAMPUS 23 VAN211 MODULE 3 - AXIAL SKELETON MESATICEPHALIC DOG BREEDS BRACHYCEPHALIC DOG BREEDS RHD/CTU-CVM BARILI CAMPUS 24 VAN211 MODULE 3 - AXIAL SKELETON C. BONES OF THE HEAD SKULL Skeleton of the head Organized into cranium & facial parts Bones of cranium = surround the brain Bones of face = surround the eyes, respiratory, & digestive passageways DOG VARIATIONS IN BREED VARIATIONS IN DOG SKULLS BONES OF THE CRANIUM Paired: occipital, parietal, frontal, temporal Unpaired: supraoccipital, interparietal, basioccipital, basisphenoid, presphenoid, ethmoid RHD/CTU-CVM BARILI CAMPUS 25 VAN211 MODULE 3 - AXIAL SKELETON BONES OF THE FACE Paired: incisive, nasal, maxilla, dorsal nasal concha, ventral nasal concha, zygomatic, palatine, lacrimal, pterygoid, mandible, lacrimal, pterygoid, mandible Unpaired: vomer ILLUSTRATIONS OF THE BONES IN DOG SKULL DESCRIPTION OF THE CRANIUM BONES Frontal forms the forehead Occipital most posterior bone of skull; forms a ring, the foramen magnum that serve as a passage of the spinal cord Parietal dorsolateral walls of skull Temporal composed of squamous, petrosal and tympanic parts and forms the lateral wall of the cranial cavity. It articulates with the frontal, parietal and sphenoid bones. RHD/CTU-CVM BARILI CAMPUS 26 VAN211 MODULE 3 - AXIAL SKELETON Interparietal bone located between occipital bone and parietal bones Sphenoid forms the base of the neurocranium and is composed of a body and wings; presphenoid (cranial); basisphenoid (caudal); helps to connect the neurocranium to the facial skeleton Ethmoid form the walls of the eye socket, or orbital cavity, as well as the roof, sides, and interior of the nasal cavity; has three parts = cribriform plate, ethmoidal labyrinth, and perpendicular plate DESCRIPTION OF THE FACIAL BONES Incissive most rostral bone, houses upper incisors Nasal form the bridge of the nose Maxilla make up most of the upper jaw, houses upper canine teeth Mandible lower jaw, houses lower teeth Palatine make up caudal hard palate Pterygoid part of the palate, behind the palatine bones Lacrimal medial part of orbit, houses part of tear drainage Zygomatic form part of eye orbit, join with temporal process Cribriform plate a bony cup in the posterior nasal cavity perforated by passageways for all olfactory nerve bundles streaming from the periphery to the brain. Vomer small, thin, plow-shaped, midline bone that occupies & divides the nasal cavity ILLUSTRATIONS OF THE BONES IN CAT SKULL THE MANDIBLE Aka the lower jawbone and houses the lower teeth. The largest bone in the skull. Facilitates jaw movement for chewing. Lower jaw is formed by two dentaries which are joined at the symphysis. There is incomplete fusion between two halves of canine mandibles. Bone consists of two parts: body and ramus Each body has alveoli for incisor, canine, premolar and molar teeth. RHD/CTU-CVM BARILI CAMPUS 27 VAN211 MODULE 3 - AXIAL SKELETON Each body has a ramus consisting of the angular, coronoid, and condylar processes. Condylar process = articulates with the temporal bone at the temporo- mandibular joint. Coronoid process = serves as an attachment point for the temporalis muscle. Angular process = projection of the posteroventral part of the dentary. Medial surface - insertion site for lateral pterygoid muscle. Lateral surface - insertion for masseter muscle. Lateral surface of ramus has a deep depression (masseteric fossa). MANDIBULAR FORAMEN Located on the medial surface of the mandibular ramus. This is the caudal opening of the mandibular canal. Serves as the entrance for the inferior alveolar nerve and blood vessels into the mandibular canal. MENTAL FORAMINA Consist of caudal, middle and rostral mental foramina. Located on the lateral surface of the mandible. These are the rostral openings of the mandibular canal. MANDIBLE, LATERAL VIEW MANDIBLE, MEDIAL VIEW MALOCCLUSIONS IN DOGS Brachygnathism Aka overbite, overshot, overjet, short lower jaw, or parrot mouth. Manifest when the mandible is shorter than the maxilla. Prognathism Aka underbite, undershot, longer lower jaw. Mandible is longer than the maxilla. Condition is the standard for brachycephalic breeds, e.g. Boxers RHD/CTU-CVM BARILI CAMPUS 28 VAN211 MODULE 3 - AXIAL SKELETON CANINE DENTAL FORMULA CANINE TEETH ERUPTION TIME GROUP TOOTH ERUPTION TIM E Incisors Central 4 months Lateral 4-5 months Medial 4-5 months Canines 5-6 months Premolars First, Fourth 4-5 months Second. Third 5-6 months Molars First 5-6 months Second 5-7 months Third 6-7 months (bottom only) BONY OSSICLES Found in the middle ear. Consist of malleus, incus, and stapes. Function: connect the tympanic membrane to the inner ear allowing for the transmission of sound waves. MALLEUS The largest and most lateral of the ear bones. Attaches loosely to the tympanic membrane via the handle of malleus. Head of malleus articulates with the incus. INCUS The incus is the second ossicle. Consists of a body and two limbs. The body articulates with the malleus. The short limb attaches to the posterior wall of the middle ear. The long limb articulates with the stapes. STAPES The stapes is the third ossicle and known as the smallest bone in the body. It is stirrup-shaped, with a head, two limbs, and a base. The head articulates with the incus, and the base joins the oval window. RHD/CTU-CVM BARILI CAMPUS 29 VAN211 MODULE 3 - AXIAL SKELETON BONY OSSICLES D. VERTEBRAL COLUMN FEATURES Regions: cervical, thoracic, lumbar, sacral, caudal 7 cervical, 13 thoracic, 7 lumbar, 3 sacral vertebrae 20-23 caudal vertebrae (vary based on tail length) PARTS OF A VERTEBRA Neural spine = projects dorsally, for attachment of muscles Neural canal = passage of the spinal cord Transverse processes = project from each side of vertebra for attachment of muscles & ligaments Centrum = a solid piece of bone below the neural canal Facet = a small, smooth, flat or slight depressed on the bone usually in point of contact with another bone Zygapophysis = articular surfaces for joining successive vertebrae Prezygapophysis: bears a facet that faces dorsally or dorsomedially Postzygapophysis: faces ventrally or ventromedially Prezygapophysis slips under preceeding postzygapophysis E. BONES OF THE NECK CERVICAL VERTEBRAE Support the head Allow head to move up-and-down and from side-to-side Enable dog to extend its neck forward or toward the ground Parts: C1 = atlas, C2 = axis, C3 - C7 = normal cervical vertebrae ATLAS (C1) Has a large neural canal and flat & broad transverse process Has short or absent neural spine but NO centrum / body RHD/CTU-CVM BARILI CAMPUS 30 VAN211 MODULE 3 - AXIAL SKELETON Transverse foramen allows vertebral artery, vein, and sympathetic nerves to penetrate the transverse process of atlas. Has alar notch instead of alar foramen. AXIS (C2) Has a broad & flat centrum Articulates w/ C1 thru odontoid process Has a large flattered neural spine Transverse process = pin-like structure Has a transverse foramen C3 - C7 Found in the neck region Do not have high spinous process Spinous processes gradually increase in length to the last (7th) vertebra Generally wider in body RHD/CTU-CVM BARILI CAMPUS 31 VAN211 MODULE 3 - AXIAL SKELETON C3, C4, C5, C6, C7 VERTEBRAE C3 VERTEBRA (cranial view, caudal view) HYOID APPARATUS Location: lies below the mandible in the front of the neck, within the muscle at the base of the tongue Unpaired: Basihyoid Paired: Thyrohyoid, Epihyoid, Stylohyoid, Tympanohyoid Characteristics Basihyoid has no lingual process. The epihyoid is longer than the stylohyoid. The stylohyoid is bent and twisted. The thyrohyoid is permanently attached to the body by cartilage. Function Holds the tongue and larynx in position Supports the base of tongue, pharynx, and larynx F. BONES OF THE TRUNK AND TAIL RIB CAGE Made up of thirteen thoracic vertebrae and thirteen pairs of ribs. Floor of the chest (sternum or brisket) is formed by a row of eight bones called the sternebrae (sternum or breastbone) connected by cartilage. Manubrium = the most cranial part, located in front of the second intercostal junction. Xiphoid process = the cartilaginous section at the caudal end of sternum, which is not attached to any ribs, gradually ossifies during adult life. The articulating structures of the thorax are costovertebral joints, costo- transverse joints, costochondral joints, sternocostal joints, inter- vertebral facet joints, and the intervertebral discs. RIBS True ribs (sternal ribs, ribs 1-9) = directly connected to the sternum. False ribs (asternal ribs, ribs 10-12) = indirectly connected to the sternum; they attach to the cartilage of the rib cranially, on the ventral aspect forming the costal arch. Floating rib (rib 13) = most caudal rib, whose posterior cartilage does not attach to the adjacent cartilage THORACIC VERTEBRAE (T1-T13) Found in the chest region and comprise the “withers” of the dog First nine ribs are attached to both thoracic vertebrae & sternum Last four thoracic vertebrae form the mid-back of dog Aid the attachment of ribs The vertebral bodies are wider and compressed dorsoventrally. RHD/CTU-CVM BARILI CAMPUS 32 VAN211 MODULE 3 - AXIAL SKELETON The transverse processes in the posterior of the series bear mamillary processes and in the last three accessory processes also. The posterior facets on the bodies for the heads of the ribs are absent on the last two or three, so that the head of each of the last three ribs articulates with only one corresponding centrum. Long spines provides space for attachment of shoulder & back muscles Assists in breathing along side with the ribs RIB CAGE AND STERNUM THORACIC VERTEBRA LUMBAR VERTEBRAE (L1-L7) Found in the upper abdominal region Has large flattened transverse processes Has a broad and flat neural spine Has a large and thick centrum Has well developed pre- and post- zygapophysis Have two extra paired projections called anapophysis & metapophysis for attachment of abdominal muscles Support organs of abdomen & pelvis Vital in the movement of the dog SACRUM (S1-S3) Lies between the lumbar spine & tail Forms the roof of the pelvic cavity RHD/CTU-CVM BARILI CAMPUS 33 VAN211 MODULE 3 - AXIAL SKELETON Part of the croup of the dog Has a narrow neural canal Neural spine reduced to a small notch Has a large centrum First sacral vertebra has a pair of large and wing-like transverse process and a small neural canal which gradually become narrower in the other vertebra COCCYGEAL VERTEBRAE (Co1 - Co23) Found in the tail region Most caudal portion of axial skeleton 0 (no tail) to 20-23 vertebrae Last section of the dog's spine Gradually reduce in size, losing arches and processes THE CROUP Determines the set-on of the tail Formed by sacrum and Co1 Angulation determines the tail set Fat or level croup, tail set is high Angled croup, tail set is low Angulation of the croup depends upon the curve of sacral & tail vertebrae RHD/CTU-CVM BARILI CAMPUS 34 VAN211 MODULE 3 - AXIAL SKELETON REVIEW QUESTIONS 1. List the parts of the bone and the function of each part. 2. What is the skeletal system made up of? 3. Which is the only movable bone of the skull? 4. Which vertebrae interacts with the skull, and which part of the skull does it interact with? 5. Which organs are protected by (a) the skull, (b) the rib cage, and (c) the vertebrae? 6. The bone that protects the brain is called the: (a) sternum, (b) cranium, (c) clavicle, (d) pelvis 7. Which bones compose the coxal bone? 8. The tip of a long bone is called the _________. 9. Where is the thoracic vertebrae located on a dog? REFERENCES BOOKS 1. Budras, K. D., Horowitz, A., & Berg, R. (2007). Anatomy of the dog, 5th revised ed. Hannover, Germany. 2. De Iuliis, G., & Pulerà, D. (2019). The dissection of vertebrates. Academic press. 3. Goody, P. C. (1997). Dog anatomy: a pictorial approach to canine structure. JA Allen & Co. Ltd. 4. Reece, W.O. (2009). Functional Anatomy and Physiology of Domestic Animals, 4th ed. Wiley-Blackwell, Ames, Iowa. INTERNET 1. https://en.wikivet.net 2. https://orthodog.com 3. https://anatomylearner.com 4. https://veteriankey.com/skeletal-system-2/ 5. The Rib Issue. Winter 2019. RHD/CTU-CVM BARILI CAMPUS 35
