THE SKELETAL SYSTEM CH 6 PART 2 – THE AXIAL SKELETON

AXIAL SKELETON SKULL SKULL HYOID BONE HYOID BONE VERTEBRAE VERTEBRAE RIBS RIBS STERNUM STERNUM

SKULL 2 major segments: 2 major segments: –Cranium & Facial bones PURPOSE: protects the brain and the sensory organs PURPOSE: protects the brain and the sensory organs The ONLY mobile bone is the MANDIBLE (lower jaw) The ONLY mobile bone is the MANDIBLE (lower jaw) The location that the skull bones unite is at the SUTURES or seams The location that the skull bones unite is at the SUTURES or seams sutures

* SINUSES are located within the dense portion of the skull and are air- filled cavities * They lessen bone weight, provide resonating chambers for vocalization, moisten/warm air, and are a site of mucous secretion * Sinuses are usually named for the skull bone that contains the sinus

SKULL The nostrils open into 2 major air passages that end in the throat. The nasal passages are filled with very fine scrolls of bone called TURBINATES. The turbinates are covered in pink tissue (mucosa) similar to the lining of the mouth. Air is warmed, moistened, and filtered as it passes through the turbinates in the nose on the way to the lungs. The nostrils open into 2 major air passages that end in the throat. The nasal passages are filled with very fine scrolls of bone called TURBINATES. The turbinates are covered in pink tissue (mucosa) similar to the lining of the mouth. Air is warmed, moistened, and filtered as it passes through the turbinates in the nose on the way to the lungs. turbinates

SKULL CRANIAL BONES CRANIAL BONES –FRONTAL BONES (#6) – form the forehead, the orbits, and the front portion of the cranial floor. Horns are an extension of the frontal bone Horns are an extension of the frontal bone –PARIETAL BONES (#7) – form the roof and upper part of each side of the skull –OCCIPITAL BONE (#8) – forms the back of the skull

SKULL –FORAMEN MAGNUM– opening at the base of the occipital bone that allows the spinal cord to pass from the skull to the spine –TEMPORAL BONES (#9) – form part of the cranial floor and the lower part of the sides. Contains middle and inner ear structures

SKULL FACIAL BONES FACIAL BONES –MAXILLA (#3) – bones that form the upper jaw, nose, orbits, and roof of the mouth –MANDIBLE – forms the lower jaw. Only movable bone in the skull maxilla mandible

SKULL –HYOID APPARATUS – U shaped structure made up of both bone and cartilage. Located above the larynx, below the mandible, and is suspended from the temporal bones via ligaments. Suspends the tongue, larynx, and floor of the mouth

VERTEBRAL COLUMN BACKBONE BACKBONE PURPOSE: protects the spinal cord, supports the skull and thorax, stiffens the trunk, anchors the pelvis, provides muscle attachment PURPOSE: protects the spinal cord, supports the skull and thorax, stiffens the trunk, anchors the pelvis, provides muscle attachment There are 5 types of vertebrae: cervical (C), thoracic (T), lumbar (L), sacral (S), coccygeal (Cy) There are 5 types of vertebrae: cervical (C), thoracic (T), lumbar (L), sacral (S), coccygeal (Cy)

Each vertebrae has a body and an arch. Each vertebrae has a body and an arch. –Body – bears the weight –Arch – forms the canal that houses the spinal cord Intervertebral discs are between the bodiesIntervertebral discs are between the bodies -Made of cartilage and serve as shock absorbers Processes extend out from dorsal and lateral vertebral surfacesProcesses extend out from dorsal and lateral vertebral surfaces

FORMULAS FORMULAS –DOG/CAT: C(7), T(13), L(7), S(3), Cy(6-23) –HORSE: C(7), T(18), L(7), S(5), Cy(15-21) –COW: C(7), T(13), L(6), S(5), Cy(18-21) –PIG: C(7), T(14-15), L(6- 7), S(4), Cy(20-23) –SHEEP: C(7), T(13), L(6- 7), S(4), Cy(16-18)

CERVICAL VERTEBRAE –1 st vertebrae: ATLAS: supports the skull –2 nd vertebrae: AXIS: what the atlas rotates on

THORACIC VERTEBRAE Attach to ribs Attach to ribs

THORACIC CAGE Composed of the thoracic vertebrae, ribs, costal cartilages, and sternum Composed of the thoracic vertebrae, ribs, costal cartilages, and sternum Thoracic cage protects the vital organs of the chest and allows the lungs to expand and contract during respiration Thoracic cage protects the vital organs of the chest and allows the lungs to expand and contract during respiration

RIBS RIBS RIBS –PURPOSE: form the thoracic wall and protect the heart and lungs –Flat, curved –Each rib has bony and cartilagenous components The cartilagenous component is located ventrally The cartilagenous component is located ventrally They unite at the costochondral junction They unite at the costochondral junction

RIBS –All attach to the thoracic vertebrae dorsally (the number of thoracic vertebrae = the number of ribs) –Differ in the attachment to the sternum 1 st 7-9 join directly with the sternum “TRUE RIBS” 1 st 7-9 join directly with the sternum “TRUE RIBS” The caudal ribs unite with the cartilagenous portion of the true ribs. They are called “FALSE RIBS” The caudal ribs unite with the cartilagenous portion of the true ribs. They are called “FALSE RIBS” The most caudal ribs due not unite with anything ventrally and appear to be “floating”, so they are called “FLOATING RIBS” The most caudal ribs due not unite with anything ventrally and appear to be “floating”, so they are called “FLOATING RIBS”

RIBS

STERNUM BREASTBONE BREASTBONE Located on ventral midline of chest Located on ventral midline of chest Flat bones called STERNEBRAE that connect to each other via cartilage Flat bones called STERNEBRAE that connect to each other via cartilage Most cranial aspect is the manubrium Most cranial aspect is the manubrium Most caudal aspect is the xiphoid process Most caudal aspect is the xiphoid process

LUMBAR VERTEBRAE Support the abdomen Support the abdomen

SACRAL VERTEBRAE One bone that results from the fusion of 3-5 vertebrae One bone that results from the fusion of 3-5 vertebrae Attaches to pelvis Attaches to pelvis

COCCYGEAL VERTEBRAE –Also called caudal or tail vertebrae –Can be docked- spinal cord ends near the lumbosacral junction