AXIAL SKELETON.pptx

SKELETAL SYSTEM: THE AXIAL SKELETON Chapter 7: by Tortora ROEL B. DEL ROSARIO,PTRP Instructor: Anatomy and Physiology T H E A X I A L S K E L E T O N and H O M EO S T A S I S: ►The bones of the axial skeleton contribute to homeostasis by protecting many of the body’s organ...

SKELETAL SYSTEM: THE AXIAL SKELETON Chapter 7: by Tortora ROEL B. DEL ROSARIO,PTRP Instructor: Anatomy and Physiology T H E A X I A L S K E L E T O N and H O M EO S T A S I S: ►The bones of the axial skeleton contribute to homeostasis by protecting many of the body’s organs such as the brain, spinal cord, heart, and, lungs. ► They are also important in support and calcium storage and release. ► Without bones, you could not survive. You would be unable to perform movements such as walking or grasping, and the slightest blow to your head or chest could damage your brain or heart. ►Because the skeletal system forms the framework of the body, a familiarity with the names, shapes, and positions of individual bones will help you locate and name many other anatomical features. Example : radial artery for radial pulse taking, frontal lobe, tibialis anterior muscle ► The branch of medical science concerned with the prevention or correction of disorders of the musculoskeletal system is called orthopedics. DIVISIONS OF THE SKELETAL SYSTEM ► The adult human skeleton consists of 206 named bones. ► Bones of the adult skeleton are grouped into two principal divisions: 1. the axial skeleton and the; 2. appendicular skeleton ► Table 7.1 presents the 80 bones of the axial skeleton and the 126 bones of the appendicular skeleton. ► The axial skeleton consists of the bones that lie around the longitudinal axis of the human body, an imaginary vertical line that runs through the body’s center of gravity from the head to the space between the feet: a. skull bones, b. auditory ossicles (ear bones), c. hyoid bone (see Figure 7.5), d. ribs, e. sternum (breastbone), and f. bones of the vertebral column. ► Functionally, the auditory ossicles in the middle ear, which vibrate in response to sound waves that strike the eardrum, are not part of either the axial or appendicular skeleton, but they are grouped with the axial skeleton for convenience (see Chapter 17). TYPES OF BONES ►types based on shape: 1. long, 2. short, 3. flat, 4. irregular, and 5. sesamoid 1. long bones ►have greater length than width, consist of a shaft and a variable number of extremities (ends), and are slightly curved for strength. ► A curved bone absorbs the stress of the body’s weight at several different points, so that it is evenly distributed. ►If bones were straight, the weight of the body would be unevenly distributed, and the bone would fracture more easily. ►Long bones consist mostly of compact bone tissue in their diaphyses but have considerable amounts of spongy bone tissue in their epiphyses. 1. long bones ►Long bones vary tremendously in size. Examples: 2. femur (thigh bone), 3. tibia and fibula (leg bones), 4. humerus (arm bone), 5. ulna and radius (forearm bones), 6. and phalanges (finger and toe bones). Femoral fracture with internal fixation: ►tibial fracture ►humeral fracture 2. Short bones: ►are somewhat cube-shaped and are nearly equal in length and width. ►Examples of short bones are the; 1. carpal (wrist) bones (except for the pisiform, which is a sesamoid bone) 2. Short bones: 2.2 the tarsal (ankle) bones (except for the calcaneus or heel bone, which is an irregular bone). 3. Flat bones: ►are generally thin and composed of two nearly parallel plates of compact bone tissue enclosing a layer of spongy bone tissue. ►Flat bones afford considerable protection and provide extensive areas for muscle attachment. ►Flat bones include; 1. the cranial bones, which protect the brain; 2. the sternum (breastbone) and ribs, which protect organs in the thorax; and 3. the scapulae (shoulder blades). ►scapula 4. Irregular bones: ► have complex shapes and cannot be grouped into any of the previous categories. ► They vary in the amount of spongy and compact bone present. ► Such bones include the vertebrae (backbones), hip bones, certain facial bones, and the calcaneus. 5. Sesamoid bones: ►shaped like a sesame seed. ► develop in certain tendons where there is considerable friction, tension, and physical stress, such as the palms and soles. ►the two patellae (kneecaps), large sesamoid bones located in the quadriceps femoris tendon (see Figure 11.20a on page 395) that are normally present in everyone. ►Functionally, sesamoid bones protect tendons from excessive wear and tear, and they often change the direction of pull of a tendon, which improves the mechanical advantage at a joint. NOTE: ► Sutural bones are small bones located in sutures (immovable joints in adults) between certain cranial bones.  BONE SURFACE MARKINGS ►There are two major types of surface markings: (1) Depressions and openings: ► which allow the passage of soft tissues (such as blood vessels and nerves) or form joints, and (2) processes: ► projections or outgrowths that either help form joints or serve as attachment points for connective tissue (such as ligaments and tendons). SKULL The skull (cranium): ► with its 22 bones, rests on the superior end of the vertebral column (backbone). ► The bones of the skull are grouped into two categories: 1. cranial bones and 2. facial bones. SKULL The cranial bones (brain case): ►form the cranial cavity, which encloses and protects the brain. 8 cranial bones; ► frontal bone, ► two parietal bones, ► two temporal bones, ► occipital bone, ► the sphenoid bone, and ► the ethmoid bone. SKULL 14 facial bones form the face: ► two nasal bones, ► two maxillae (or maxillas), ► two zygomatic bones, the mandible, ► two lacrimal bones, ► two palatine bones, ► two inferior nasal conchae, ► and the vomer. Figures 7.3 through 7.8 illustrate the bones of the skull from different viewing directions.  General Features and Functions of the SKULL ► Besides forming the large cranial cavity, the skull also forms several smaller cavities, including the nasal cavity and orbits (eye sockets), which open to the exterior. ►Certain skull bones also contain cavities called paranasal sinuses that are lined with mucous membranes and open into the nasal cavity. ►Other small cavities within the skull house the structures involved in hearing and equilibrium. ►the mandible is the only movable bone of the skull. ►Immovable joints called sutures fuse most of the skull bones together and are especially noticeable on the outer surface of the skull. ABLE ► The skull has many surface markings, such as foramina and fissures through which blood vessels and nerves pass. ► the cranial bones stabilize the positions of the brain, blood vessels, lymphatic vessels, and nerves through the attachment of their inner surfaces to meninges (membranes). ►The outer surfaces of cranial bones provide large areas of attachment for muscles that move various parts of the head. ►The Cranial bones also provide attachment for some muscles that produce facial expressions. The facial bones: ►form the framework of the face and provide support for the entrances to the digestive and respiratory systems. ►the cranial and facial bones protect and support the delicate special sense organs for vision, taste, smell, hearing, and equilibrium (balance). 1. Frontal Bone ► The frontal bone forms the forehead (the anterior part of the cranium), the roofs of the orbits (eye sockets), and most of the anterior part of the cranial floor (Figure 7.3). 2. Parietal Bones ► The (2) parietal bones form the greater portion of the sides and roof of the cranial cavity (Figure 7.4). ► The internal surfaces of the parietal bones contain many protrusions and depressions that accommodate the blood vessels supplying the dura mater, the superficial connective tissue covering of the brain. 3. Temporal Bones ► The paired temporal bones form the inferior lateral aspects of the cranium and part of the cranial floor. ►In Figure 7.4, note the temporal squama ( scale), the thin, flat part of the temporal bone that forms the anterior and superior part of the temple. ► zygomatic process, which articulates (forms a joint) with the temporal process of the zygomatic (cheek) bone. ►zygomatic arch. ► A socket called the mandibular fossa ► mandibular fossa (as seen in the above figures) ► temporomandibular joint (TMJ). 3. Temporal Bones ► external auditory meatus (meatus passageway), or ear canal, which directs sound waves into the ear. ► In an adult, this portion of the bone contains several mastoid air cells. ► These tiny airfilled compartments are separated from the brain by thin bony partitions. ►In cases of mastoiditis (inflammation of the mastoid air cells caused, for example, by a middle-ear infection), the infection may spread to the brain. ►mastoid process is a rounded projection of the mastoid portion 3. Temporal Bones ► It is the point of attachment for several neck muscles. The internal auditory meatus (Figure 7.5): ►is the opening through which the facial (VII) nerve and vestibulocochlear (VIII) nerve pass. The styloid process: ► projects inferiorly from the inferior surface of the temporal bone and serves as a point of attachment for muscles and ligaments of the tongue and neck (see Figure 7.4). the stylomastoid foramen: ►through which the facial (VII) nerve and stylomastoid artery pass (see Figure 7.7). 3. Temporal Bones petrous portion ( petrous rock) of the temporal bone (see Figure 7.8a). ► located at the base of the skull ► houses the internal ear and the middle ear, structures involved in hearing and equilibrium (balance). carotid foramen: ►through which the carotid artery passes (see Figure 7.7). the jugular foramen: ►a passageway for the jugular vein. 4. Occipital Bone ►forms the posterior part and most of the base of the cranium (Figure 7.6; also see Figure 7.4). The foramen magnum ( large hole): ► is in the inferior part of the bone. ►The medulla oblongata (inferior part of the brain) connects with the spinal cord within this foramen, and the vertebral and spinal arteries also pass through it. The occipital condyles(Figure 7.7): ►articulate with depressions on the first cervical vertebra (atlas) to form the atlanto-occipital joint, which allows you to nod your head “yes.”/ YES JOINT” 4. Occipital Bone The external occipital protuberance: ►is the most prominent midline projection on the posterior surface of the bone just above the foramen magnum. ► You may be able to feel this structure as a bump on the back of your head, just above your neck. (See Figure 7.4.) the ligamentum nuchae: ► A large fibrous, elastic ligament, extends from the external occipital protuberance to the seventh cervical vertebra to help support the head. 5. Sphenoid Bone ►lies at the middle part of the base of the skull (Figures 7.7 and 7.8). ►is the keystone of the cranial floor because it articulates with all the other cranial bones, holding them together. ► The shape of the sphenoid resembles a butterfly with outstretched wings (Figure 7.8b). ► The space inside the body is the sphenoidal sinus, which drains into the nasal cavity (see Figure 7.13). The sella turcica: ►sella => saddle; turcica Turkish) ► is a bony saddle-shaped structure on the superior surface of the body of the sphenoid (Figure 7.8a) hypophyseal fossa: ► which contains the pituitary gland. greater wings of the sphenoid: ►form the anterolateral floor of the cranium. ►also form part of the lateral wall of the skull lesser wings of the sphenoid bone: ►They form part of the floor of the cranium and the posterior part of the orbit of the eye. the optic foramen or canal (optic eye): ►through which the optic (II) nerve and ophthalmic artery pass into the orbit. superior orbital fissure: ► Figure 7.12. Blood vessels and cranial nerves pass through. ► At the base of the lateral pterygoid process in the greater wing is the foramen ovale ( oval hole). The foramen lacerum ( lacerated): ►It transmits a branch of the ascending pharyngeal artery. foramen rotundum ( round hole): ►The maxillary branch of the trigeminal (V) nerve passes through the foramen rotundum. 6. Ethmoid Bone ►The ethmoid bone forms; (1)part of the anterior portion of the cranial floor; (2) the medial wall of the orbits; (3)the superior portion of the nasal septum, a partition that divides the nasal cavity into right and left sides; and (4)most of the superior sidewalls of the nasal cavity. ► The ethmoid bone is a major superior supporting structure of the nasal cavity. The cribriform plate: ►forms the roof of the nasal cavity. ► The cribriform plate contains the olfactory foramina (olfact- to smell) through which the olfactory nerves pass. the crista galli: ►which serves as a point of attachment for the membranes that separate the two sides of the brain. ETHMOIDAL CELLS: ►They contain 3 to 18 air spaces called ethmoidal cells. ►The ethmoidal cells together form the ethmoidal sinuses (see Figure 7.13). the superior nasal concha or turbinate and the middle nasal concha (turbinate). ►The conchae greatly increase the vascular and mucous membrane surface area in the nasal cavity, which warms and moistens (humidifies) inhaled air before it passes into the lungs. ►The conchae also cause inhaled air to swirl, and the result is that many inhaled particles become trapped in the mucus that lines the nasal cavity. ►This action of the conchae helps cleanse inhaled air before it passes into the rest of the respiratory passageways. ►The superior nasal conchae are near the olfactory foramina of the cribriform plate where the sensory receptors for olfaction (smell) terminate in the mucous membrane of the superior nasal conchae. ►Thus, they increase the surface area for the sense of smell. Facial Bones ►The shape of the face changes dramatically during the first two years after birth. ►The brain and cranial bones expand, the first set of teeth form and erupt (emerge), and the paranasal sinuses increase in size. ►Growth of the face ceases at about 16 years of age. The 14 facial bones include; ► two nasal bones, ► two maxillae (or maxillas), ► two zygomatic bones, ► the mandible, ► two lacrimal bones, ► two palatine bones, ► two inferior nasal conchae, and ► the vomer. 1. Nasal Bones ►form the bridge of the nose. 2. Maxillae ►The paired maxillae unite to form the upper jawbone. ►They articulate with every bone of the face except the mandible (lower jawbone) (see Figures 7.4 and 7.7). The hard palate: ►is the bony roof of the mouth. ►The hard palate separates the nasal cavity from the oral cavity. ► The palatine process is a horizontal projection of the maxilla that forms the anterior three-quarters of the hard palate. ►The union and fusion of the maxillary bones normally is completed before birth. ►If this fusion fails, this condition is referred to as a cleft palate. The infraorbital foramen: ►allows passage of the infraorbital nerve and blood vessels and a branch of the maxillary division of the trigeminal (V) nerve. the incisive foramen ( incisor teeth) just posterior to the incisor teeth (see Figure 7.7). ►It transmits branches of the greater palatine blood vessels and nasopalatine nerve. Zygomatic Bones ►The two zygomatic bones, commonly called cheekbones. Lacrimal Bones ►the smallest bones of the face. ►contain a lacrimal fossa, a vertical groove formed with the maxilla, that houses the lacrimal sac, a structure that gathers tears and passes them into the nasal cavity (see Figure 7.12). Palatine Bones ► The two L-shaped palatine bones form the posterior portion of the hard palate, part of the floor and lateral wall of the nasal cavity. Inferior Nasal Conchae ►All three pairs of nasal conchae (superior, middle, and inferior) increase the surface area of the nasal cavity and help swirl and filter air before it passes into the lungs. ►only the superior nasal conchae of the ethmoid bone are involved in the sense of smell. Vomer ► a roughly triangular bone on the floor of the nasal cavity. ►It forms the inferior portion of the nasal septum. Mandible ►or lower jawbone, is the largest, strongest facial bone (Figure 7.10). ► It is the only movable skull bone (other than the auditory ossicles). ► has a posterior condylar process that articulates with the mandibular fossa and articular tubercle of the temporal bone (see Figure 7.4) to form the temporomandibular joint (TMJ). The alveolar process: ►is an arch containing the alveoli (sockets) for the mandibular (lower) teeth. The mental foramen: ►approximately inferior to the second premolar tooth. ►It is near this foramen that dentists reach the mental nerve when injecting anesthetics. the mandibular foramen: ►another site often used by dentists to inject anesthetics. ►is the beginning of the mandibular canal. ► Through the canal pass the inferior alveolar nerves and blood vessels, which are distributed to the mandibular teeth. Nasal Septum ► separates right and left side of the nasal cavity which consists of bone and cartilage. ► has 3 components; 1. the vomer, 2. septal cartilage, and the 3. perpendicular plate of the ethmoid bone (Figure 7.11). ► The term “broken nose,” in most cases refers to damage to the septal cartilage rather than the nasal bones themselves. Orbits ►contains the eyeball and associated structures (Figure 7.12). ►The three cranial bones of the orbit are the frontal, sphenoid, and ethmoid; the four facial bones are the palatine, zygomatic, lacrimal, and maxilla. Foramina ►foramina (openings for blood vessels, nerves, or ligaments) of the skull in the descriptions of the cranial and facial bones that they penetrate. Sutures ►A suture is an immovable joint in most cases in an adult skull that holds most skull bones together. ►Sutures in the skulls of infants and children often are movable. 1. The coronal suture: unites the frontal bone and both parietal bones (see Figure 7.4). 2. The sagittal suture: unites the two parietal bones on the superior midline of the skull. ► The sagittal suture is so named because in the infant, before the bones of the skull are firmly united, the suture and the fontanels (soft spots) associated with it resemble an arrow. 3. The lambdoid suture: ►unites the two parietal bones to the occipital bone. Figure 7.6. 4. The squamous sutures: ►unite the parietal and temporal bones on the lateral aspects of the skull (see Figure 7.4). Paranasal Sinuses ►are cavities within certain cranial and facial bones near the nasal cavity. ►most evident in a sagittal section of the skull (Figure 7.13). ►lined with mucous membranes that are continuous with the lining of the nasal cavity. ►Secretions produced by the mucous membranes of the paranasal sinuses drain into the nasal cavity. ►Paranasal sinuses are not present at birth, but develop during the prepubescent years as outgrowths of the nasal mucosa (prepubescent means before becoming capable of reproduction, typically the early to mid-teenage years). Paranasal Sinuses ► Skull bones containing the paranasal sinuses are the; 1. frontal, 2. sphenoid, 3. ethmoid, and 4. maxillary. ►The sinuses lighten the mass of the skull and increase the surface area of the nasal mucosa, thus increasing the production of mucus to help moisten and cleanse inhaled air. ►the paranasal sinuses serve as resonating (echo) chambers within the skull that intensify and prolong sounds, thereby enhancing the quality of the voice. Paranasal Sinuses: ►The influence of the sinuses on your voice becomes obvious when you have a cold; the passageways through which sound travels into and out of the sinuses become blocked by excess mucus production, changing the quality of your voice. Fontanels ►The skeleton of a newly formed embryo consists of cartilage or mesenchyme. ► At birth, mesenchyme-filled spaces called fontanels (fon-ta-NELZ little fountains), commonly called “soft spots,” are present between the cranial bones (Figure 7.14). ► Fontanels are areas of unossified mesenchyme. ► the fontanels provide some flexibility to the fetal skull, allowing the skull to change shape as it passes through the birth canal and later permitting rapid growth of the brain during infancy. 1. unpaired anterior fontanel: ►the largest fontanel, is located at the midline between the two parietal bones and the frontal bone, and is roughly diamond-shaped. ►It usually closes 18 to 24 months after birth. ►the anterior fontanel serves as a landmark for withdrawal of blood for analysis from the superior sagittal sinus (a large vein on the midline surface of the brain). 2. The unpaired posterior fontanel: ►is located at the midline between the two parietal bones and the occipital bone. ►Because it is much smaller than the anterior fontanel, it generally closes about 2 months after birth. 3. The paired anterolateral fontanels: ►located laterally between the frontal, parietal, temporal, and sphenoid bones, are small and irregular in shape. ► Normally, they close about 3 months after birth. 4. The paired posterolateral fontanels: ►located laterally between the parietal, occipital, and temporal bones, are irregularly shaped. ► They begin to close 1 to 2 months after birth, but closure is generally not complete until 12 months. ►The amount of closure in fontanels helps a physician gauge the degree of brain development. HYOID BONE ►( U-shaped); does not articulate with any other bone. ►it is suspended from the styloid processes of the temporal bones by ligaments and muscles. ►Located in the anterior neck between the mandible and larynx (Figure 7.15a) ►the hyoid bone supports the tongue, providing attachment sites for some tongue muscles and for muscles of the neck and pharynx. HYOID BONE ► The hyoid bone also helps to keep the larynx (voice box) open at all times. ► The hyoid bone and the cartilages of the larynx and trachea are often fractured during strangulation. ► As a result, they are carefully examined at autopsy when strangulation is a suspected cause of death. VERTEBRAL COLUMN ►also called the spine, backbone, or spinal column. ►is composed of a series of bones called vertebrae. ►The vertebral column, the sternum, and the ribs form the skeleton of the trunk of the body. ►about (28 in.) in an average adult male and ►about 61 cm (24 in.) in an average adult female. ► the vertebral column functions as a strong, flexible rod with elements that can move forward, backward, and sideways, and rotate. ►to enclosing and protecting the spinal cord, it supports the head, and serves as a point of attachment for the ribs, pelvic girdle, and muscles of the back and upper limbs. ►The total number of vertebrae during early development is 33. ► As a child grows, several vertebrae in the sacral and coccygeal regions fuse. ► As a result, the adult vertebral column typically contains 26 vertebrae (Figure 7.16a). ► These are distributed as follows: 7 cervical vertebrae are in the neck region. 12 thoracic vertebrae (thorax chest) are posterior to the thoracic cavity. 5 lumbar vertebrae support the lower back. 1 sacrum sacred bone) consists of five fused sacral vertebrae. 1 coccyx because the shape resembles the bill of a cuckoo bird) usually consists of four fused coccygeal vertebrae. ►The cervical, thoracic, and lumbar vertebrae are movable, but the sacrum and coccyx are not. Normal Curves of the Vertebral Column ►anterior or posterior, a normal adult vertebral column appears straight. ►when viewed from the side, it shows four slight bends called normal curves (Figure 7.16b). ►The curves of the vertebral column increase its strength, help maintain balance in the upright position, absorb shocks during walking, and help protect the vertebrae from fracture. ►The fetus has a single anteriorly concave curve (Figure 7.16c). Normal Curves of the Vertebral Column ► At about the third month after birth, when an infant begins to hold its head erect, the cervical curve develops. ►when the child sits up, stands, and walks, the lumbar curve develops. ► The thoracic and sacral curves are called primary curves because they form first during fetal development. ►The cervical and lumbar curves are known as secondary curves because they begin to form later, several months after birth. Normal Curves of the Vertebral Column ► All curves are fully developed by age 10. ► secondary curves may be progressively lost in old age. ► Various conditions may exaggerate the normal curves of the vertebral column, or the column may acquire a lateral bend, resulting in abnormal curves of the vertebral column. ► 3 abnormal curves—kyphosis, lordosis, and scoliosis. Intervertebral Discs ►found between the bodies of adjacent vertebrae from the second cervical vertebra to the sacrum (Figure 7.16d) ►account for about 25% of the height of the vertebral column. ►has an outer fibrous ring consisting of fibrocartilage called the annulus fibrosus (annulus ringlike) ► and an inner soft, pulpy, highly elastic substance called the nucleus pulposus (pulposus pulplike). ► The discs form strong joints, permit various movements of the vertebral column, and absorb vertical shock. Intervertebral Discs ►Under compression, they flatten and broaden. ►During the course of a day the discs compress so that we are a bit shorter at night. ►While we are sleeping there is less compression so that we are taller when we awaken in the morning. ►With age, the nucleus pulposus hardens and becomes less elastic. ►Narrowing of the discs and compression of vertebrae results in a decrease in height with age. Intervertebral Discs ►intervertebral disc are avascular, the annulus fibrosus and nucleus pulposus rely on blood vessels from the bodies of vertebrae to obtain oxygen and nutrients and remove wastes. ►Certain stretching exercises, such as yoga, decompress discs and increase blood circulation, both of which speed up the uptake of oxygen and nutrients by discs and the removal of wastes. Parts of a Typical Vertebra ► Vertebrae in different regions of the spinal column vary in size, shape, and detail, but they are similar enough that we can discuss the structures (and the functions) of a typical vertebra (Figure 7.17). ►Vertebrae typically consist of; 1. a body, 2. a vertebral arch, and 3. several processes. Body ►is the weightbearing part of a vertebra. ►The anterior and lateral surfaces contain nutrient foramina, openings through which blood vessels deliver nutrients and oxygen and remove carbon dioxide and wastes from bone tissue. Vertebral Arch ► Two short, thick processes, the pedicles project posteriorly from the vertebral body to unite with the flat laminae, to form the vertebral arch. ► The vertebral foramen contains the spinal cord, adipose tissue, areolar connective tissue, and blood vessels. intervertebral foramen: ►permits the passage of a single spinal nerve that passes to a specific region of the body. Processes ► a transverse process extends laterally on each side. ► A single spinous process (spine) projects posteriorly from the junction of the laminae. ►These 3 processes serve as points of attachment for muscles. ►The articulating surfaces of the articular processes, which are referred to as facets, are covered with hyaline cartilage.  Regions of the Vertebral Column Cervical Region ►The bodies of the cervical vertebrae (C1–C7) are smaller than all other vertebrae except those that form the coccyx (Figure 7.18a). ► Their vertebral arches, are larger. ► All cervical vertebrae have three foramina: 1 vertebral foramen and 2 transverse foramina (Figure 7.18d). ►The vertebral foramina of cervical vertebrae are the largest in the spinal column because they house the cervical enlargement of the spinal cord. ►Each cervical transverse process contains a transverse foramen through which the vertebral artery and its accompanying vein and nerve fibers pass. ► The first two cervical vertebrae differ considerably from the others. ATLAS (C1): ►named after the mythological Atlas who supported the world on his shoulders, is the first cervical vertebra inferior to the skull (Figure 7.18a, b). ►The atlas is a ring of bone with anterior and posterior arches and large lateral masses. ► It lacks a body and a spinous process. ► They articulate with the occipital condyles of the occipital bone to form the paired atlanto-occipital joints. ► These articulations permit you to move your head to signify “yes joint.” Second cervical vertebra (C2): ► the axis (see Fig-ure 7.18a, c), does have a body. ► A peglike process called the dens ( tooth) or odontoid process projects superiorly through the anterior portion of the vertebral foramen of the atlas. ► The dens makes a pivot on which the atlas and head rotate. ► This arrangement permits side-to-side movement of the head, as when you move your head to signify “no joint.” C1-C2 joint : ► is called the atlanto-axial joint. ► In some instances of trauma, the dens of the axis may be driven into the medulla oblongata of the brain. ►This type of injury is the usual cause of death from whiplash injuries. The seventh cervical vertebra (C7): ►called the vertebra prominens, is somewhat different (see Figure 7.18a). ► Its single large spinous process may be seen and felt at the base of the neck. Thoracic Region ► Thoracic vertebrae (T1–T12; Figure 7.19) are considerably larger and stronger than cervical vertebrae. ► In addition, the spinous processes on T1 and T2 are long, laterally flattened, and directed inferiorly. ► thoracic vertebrae also have longer and larger transverse processes. ► The feature of the thoracic vertebrae is that they articulate with the ribs. Except for T11 and T12, the transverse processes have facets for articulating with the tubercles of the ribs. Thoracic Region ► The articulations between the thoracic vertebrae and ribs, called vertebrocostal joints, occur on both sides of the vertebral body. ► Movements of the thoracic region are limited by the attachment of the ribs to the sternum. Lumbar Region ► The lumbar vertebrae (L1–L5) are the largest and strongest of the unfused bones in the vertebral column (Figure 7.20 on page 224) because the amount of body weight supported by the vertebrae increases toward the inferior end of the backbone. ► The spinous processes are quadrilateral in shape, thick and broad, and project nearly straight posteriorly. ► The spinous processes are well adapted for the attachment of the large back muscles. Sacrum ► The sacrum is a triangular bone formed by the union of five sacral vertebrae (S1–S5) (Figure 7.21a on page 225). ► The sacral vertebrae begin to fuse in individuals between 16 and 18 years of age, a process usually completed by age 30. ► Positioned at the posterior portion of the pelvic cavity medial to the two hip bones, the sacrum serves as a strong foundation for the pelvic girdle. ►The female sacrum is shorter, wider, and more curved between S2 and S3 than the male sacrum (see Table 8.1 on page 249). ► four pairs of posterior sacral foramina (Figure 7.21b). These foramina connect with anterior sacral foramina to allow passage of nerves and blood vessels ► The superior articular processes of the sacrum articulate with the inferior articular processes of the fifth lumbar vertebra, and the base of the sacrum articulates with the body of the fifth lumbar vertebra to form the lumbosacral joint. Coccyx ► The coccyx, like the sacrum, is triangular in shape. ► It is formed by the fusion of usually four coccygeal vertebrae, indicated in Figure 7.21 as Co1–Co4. ► The coccygeal vertebrae fuse somewhat later than the sacral vertebrae, between the ages of 20 and 30. ► In females, the coccyx points inferiorly to allow the passage of a baby during birth; in males, it points anteriorly (see Table 8.1 on page 249). THORAX ► The term thorax refers to the entire chest. The skeletal part of the thorax, the thoracic cage, is a bony enclosure formed by the sternum, ribs and their costal cartilages, and the bodies of the thoracic vertebrae (Figure 7.22). ► The costal cartilages attach the ribs to the sternum. ► It encloses and protects the organs in the thoracic and superior abdominal cavities, provides support for the bones of the upper limbs, and plays a role in breathing. Sternum ► The sternum, or breastbone, is a flat, narrow bone located in the center of the anterior thoracic wall that measures about 15 cm (6 in.) in length and consists of three parts (Figure 7.22). ► has manubrium, the middle and largest part is the body; and the inferior, smallest part is the xiphoid process. ►Incorrect positioning of the hands of a rescuer during cardiopulmonary resuscitation (CPR) may fracture the xiphoid process, driving it into internal organs. Sternum ► During thoracic surgery, the sternum may be split along the midline and the halves spread apart to allow surgeons access to structures in the thoracic cavity such as the thymus, heart, and great vessels of the heart. ► After surgery, the halves of the sternum are held together with wire sutures. Ribs ► Twelve pairs of ribs, numbered 1–12 from superior to inferior, give structural support to the sides of the thoracic cavity (Figure 7.22b). ► The ribs increase in length from the first through seventh, and then decrease in length to the twelfth rib. ► Each rib articulates posteriorly with its corresponding thoracic vertebra. ► The first through seventh pairs of ribs have a direct anterior attachment to the sternum by a strip of hyaline cartilage called costal cartilage (cost- rib). ► The costal cartilages contribute to the elasticity of the thoracic cage and prevent various blows to the chest from fracturing the sternum and/or ribs. ► The ribs that have costal cartilages and attach directly to the sternum are called true (vertebrosternal) ribs. ► The articulations formed between the true ribs and the sternum are called sternocostal joints. ► The remaining five pairs of ribs are termed false ribs because their costal cartilages either attach indirectly to the sternum or do not attach to the sternum at all. ► The cartilages of the eighth, ninth, and tenth pairs of ribs attach to one another and then to the cartilages of the seventh pair of ribs. ► These false ribs are called vertebrochondral ribs. ► The eleventh and twelfth pairs of ribs are false ribs designated as floating (vertebral) ribs because the costal cartilage at their anterior ends does not attach to the sternum at all. ► These ribs attach only posteriorly to the thoracic vertebrae. ► Inflammation of one or more costal cartilages, called costochondritis, is characterized by local tenderness and pain in the anterior chest wall that may radiate. ► The symptoms mimic the chest pain associated with a heart attack (angina pectoris). THANK YOU! Sir Roel