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Skeletal System Chapter 8/Part II Joe Pistack, MS/Ed
Divisions of the Skeletal System Skeletal system is divided into two sections: (1)-Axial Skeleton (2)-Appendicular Skeleton
The Axial Skeleton The Axial Skeleton includes: Bones of the skull Hyoid bone Bones of the middle ear Vertebral column Bony thorax
The Appendicular Skeleton The Appendicular Skeleton includes: Bones of the arms and legs Bones of the hips Bones of the shoulder girdles
The Cranium Bony structure that encases and protects the brain. Composed of 8 bones: Frontal 1 Parietal 2 Temporal 2 Occipital 1 Sphenoid 1 Ethmoid 1
The Cranium Frontal Bone: Forms the forehead and the upper part of the bony structure surrounding the eyes.
The Cranium Parietal bones: (2) Form the upper sides of the head and the roof of the cranial cavity.
The Cranium Temporal Bones: (2) Located on both sides of the Head close to the ears, commonly called the Temples.
The Cranium Important Bone Markings Found on the temporal bones: (1)-External auditory meatus Opening for the ear. (2)-Zygomatic Process-forms part of the cheek-bone. (3)-Styloid Process-sharp projection used as a point of attachment for some of the muscles associated with the tongue and larynx.
The Cranium (4) Mastoid Process: Forms a point of attachment for some of the muscles of the neck.
The Cranium Occipital Bone: Located at the base of the skull. Foramen magnum-large hole in the occipital bone, allows the brainstem to extend downward as the spinal cord.
The Cranium Sphenoid Bone: Butterfly bone that forms part of the floor and sides of the cranium. Also forms part of the orbits surrounding the eyes. Sella Turcica-depression in the midline of the sphenoid bone, forms the seat for the pituitary gland. (also called Turk’s saddle)
The Cranium Ethmoid Bone: An irregularly shaped bone located between the eye orbits, helps to form the bony structure of the nasal cavity.
Facial Bones Facial Bones: (14) Mandible-lower jaw bone, carries the lower teeth. Anterior portion of the mandible forms the chin. Forms the only freely movable joint in the skull. Temporomandibular joint (TMJ)-depression in front of the ear. Tension or stress cause pain.
Facial Bones Maxilla: Carries the upper teeth. An extension of the maxilla is the palatine process, this forms the anterior portion of the hard palate (roof) of the mouth. These bones also form parts of the nasal cavity and the eye orbits.
Facial Bones Palatine Bones: (2) Form the posterior part of the hard palate and the floor of the nasal cavity
Facial Bones Failure of the palatine and maxillary bones to fuse causes a condition known as Cleft palate. This makes it very difficult for an infant to suck. Can be surgically repaired.
Facial Bnes Zygomatic Bones: The cheekbones, also form part of the orbits of the eyes.
Facial Bones Several other bones complete the facial structure: Lacrimal bones The nasal bones The vomer The inferior nasal conchae
Broken Jaw Usually the result of trauma or automobile accident. Cannot cast, must be immobilized by wiring it to the upper jaw. Patient cannot talk, eat or vomit. Wire cutters need to be on hand in case of vomiting.
Sinuses Sinuses-air-filled cavities located in several bones of the skull. Two important functions: (1)-lessen the weight of the skull. (2)-increase the sound of the voice. Paranasal sinuses- four sinuses that surround and connect with the nasal structures.
Sinuses Sinusitis-a sinus infection characterized by stuffiness and pain in the overlying facial region. Allergies cause the membranes that line the facial sinuses to over secrete mucous. Mucous forms a medium for bacterial growth. As the mucous accumulates, the membranes swell causing pressure and discomfort in the facial region which overlies the sinuses.
Sutures Suture- joining of the bones of the skull together, much like a zipper. Major Sutures: Coronal suture Lambdoidal suture Squamosal suture
The Infant Skull Fontanels-soft areas that have not yet been converted to bone. The rhythm of the baby’s pulse can be found in these soft spots. Two Major Fontanels: (1)-larger, diamond-shaped anterior fontanel. (2)-smaller, posterior, triangular occipital fontanel. Fontanels are usually closed by the age of two years.
The Infant Skull
Microcephalia-a condition where the sutures of the brain fuse too early, this is characterized by a small skull and impaired intellectual functioning.
The Infant Skull Hydrocephalus-occurs when the skull expands too much from an excessive accumulation of fluid, the bones are forced apart and the skull enlarges.
Hyoid Bone Hyoid Bone-U shaped bone located in the upper neck. Anchors the tongue and is associated with swallowing. Often fractured during strangulation.
Vertebral Column Also called backbone- extends from the skull to the pelvis. Consists of 26 bones called vertebrae. Vertebrae are stacked in a column.
The Vertebral Column Four Major functions of the vertebral column: (1) forms a supporting structure for head and thorax. (2) forms an attachment for the pelvic girdle. (3) encases and protects the spinal cord. (4) provides flexibility for the body.
The Vertebral Column Vertebrae are named according to their location in the body. (C1 to C7)- seven cervical located in the neck region. Vertebra prominens-C7- used as a landmark in assessing surface anatomy.
The Vetebral column C7:-vetebra prominens: Feels like a large bump.
Vertebral Column 12 Thoracic Vertebrae (T1 to T 12) Located in the chest region. 5 Lumbar Vertebrae (L1 to L5) Located in the lower back Region. 5 Sacral Vertebrae fuse into one sacrum.
The Vertebral Column The sacrum forms the posterior wall of the pelvis. Four small vertebrae fuse Into the tailbone. The tailbone is also called The coccyx.
C1 and C2 Atlas-C1: First cervical vertebrae. No body (thick solid section that other vertebrae have) but has depressions into which fit the bony projections of the occipital bone of the skull. Atlas supports the skull and allows you to nod “yes”.
C1 and C2 Axis (C2): Has a toothlike projection called the dens that fits into the atlas and acts as a pivot or swivel for the atlas. Allows you to rotate your head from side to side to say “no”.
Characteristics of Vertebrae Vertebrae are irregular bones that contain several distinct structures. Body of the vertebrae is padded by a cartilaginous disc called an intervertebral disc. Supports the weight of the vertebrae sitting on top of it.
Vertebrae Vertebral column – also known as the spine. Vertebrae become larger as the vertebral column descends. Larger, lower vertebrae carry a heavier load. Vertebral foramen –opening for the spinal cord.
Abnormalities of the Vertebral Column Spina Bifida –failure of the lamina of the vertebra to fuse during fetal development. Lamina-bone that forms a protective ring around the vertebrae.
Abnormalities of the Vertebral Column Spina Bifida –defect allows the spinal cord to protrude onto the surface of the back. Compression of the spinal cord causes paralysis and loss of bladder and bowel control.
Abnormalities of the Vertebral Column Discs may become damaged or may be called a “slipped” disc. The spinal cord descends from the base of the brain through the vertebral foramen so injury at any point can compress or sever the spinal cord, causing paralysis. Laminectomy –surgical procedure used to access the intervertebral discs.
Curvatures The vertebral column has four normal curvatures: (1)-cervical (2)-thoracic (3)-lumbar (4)-sacral The cervical and lumbar curvatures bend toward the front of the body. The thoracic and sacral curvatures bend away from the body.
Abnormal Curvatures Scoliosis – Lateral curvature. Usually involves the thoracic vertebrae. Severe can compress abdominal organs. May diminish expansion of the rib cage and impair breathing.
Abnormal Curvatures Kyphosis – Exaggerated thoracic curvature. Can impair breathing Sometimes called hunchback.
Abnormal Curvatures Lordosis – Exaggerated lumbar curvature. Sometimes called swayback. Causes of abnormal curvatures: (1)-genetic defect. (2)-response to a disease. (3)-poor posture
Thoracic Cage The thoracic cage is the bony, cone-shaped cage that surrounds and protects the lungs, heart, large blood vessels, liver and spleen. Plays a crucial role in breathing and helps to support the bones of the shoulder.
Sternum Sternum: Also called breastbone. Dagger shaped. Located along the midline of the anterior chest. Sternum has 3 parts: (1) manubrium (2)body (3) xiphoid process (tip of the sternum).
Ribs Ribs-(12) pair: Posteriorly, twelve pairs of ribs attach to the thoracic vertebrae. Anteriorly, the top seven pairs of ribs attach directly to the sternum by costal cartilage. These are the true ribs.
Ribs False Ribs: The lower five pair of ribs that attach indirectly to the sternum or not at all. Floating Ribs: The bottom two pair of false ribs that lack sternal attachment.
Ribs Floating ribs are the most easily broken because of their location and lack of attachment. Ribs are numbered to describe location of the thoracic structures. Eg. The heart is located between the 2 nd and 6 th ribs. Intercostal muscles are located between the ribs, contraction of these muscles helps move the thoracic cage during breathing.
Appendicular Skeleton Appendicular skeleton is composed of bones of : The shoulder girdle Upper limbs Pelvic girdle Lower limbs
Appendicular Skeleton Shoulder Girdle- Also called pectoral girdle. Each shoulder contains: One clavicle One scapula
Appendicular Skeleton Functions of the shoulder: Supports the arms. Serves as a place of attachment for the muscles. Area of great flexibility.
Appendicular Skeleton Clavicle: Also called the collarbone. Looks like a long, slender, S-shaped rod. Articulates with the sternum and the scapula. Attachment is weak and easily dislocated. Most frequently broken bone in the body.
Appendicular Skeleton Glenoid Cavity: Located on the scapula, site where the head of the humerus fits, allowing you to rotate your shoulder. Acromion Process and coracoid process on the scapula serve as points of attachment for ligaments and muscles.
Upper Extremities Upper Limb contains: Bones of the upper arm (humerus). The forearm (ulna and radius). The hand, (carpals, metacarpals and phalanges).
Upper Extremities Humerus: Long bone of the upper arm. Contains a head which fits into the glenoid cavity of the scapula that allows the upper arm to rotate at the shoulder joint.
Upper Extremities Distal head of the humerus contains several processes that allow it to articulate with the bones of the lower arm: Olecranon fossa- depression of the humerus that holds the olecranon process of the ulna when the elbow is extended.
Upper Extremities Radius: One of two bones of the forearm. Located on the “thumb side” when the palm of the hand is facing forward. Head of the radius articulates with the humerus, ulna and carpal bones.
Upper Extremities Ulna: Second bone of the forearm. Ulna is the longer of the two bones. Located on the little-finger side of the forearm.
Upper Extremities Ulna: Ulna contains processes and depressions that allow it to articulate with the humerus, radius and carpal bones. Olecranon process of the ulna is what you feel as the bony point of the elbow.
Upper Extremities Supination-palm up-two bones are parallel. Pronation-palm down-the bones cross to achieve this movement.
Upper Extremities Hand: Composed of a wrist, palm and fingers. Wrist contains eight carpal bones, which are tightly bound by ligaments. Five metacarpal bones form the palm of the hand. Each metacarpal bone is in line with a finger.
Upper Extremities Hand: Phalanges-14 finger bones, also called digits. Each digit has three bones except the thumb, which only has two bones. The thumb is also called the pollex.
Pelvic Girdle Pelvic Girdle: Composed of two coxal bones that articulate with each other anteriorly and with the sacrum posteriorly.
Pelvic Girdle Pelvic Girdle performs three functions: (1) Bears the weight of the body. Serves as a place of attachment for the legs. Protects the organs located in the pelvic cavity.
Pelvis Pelvis is formed by: The pelvic girdle Sacrum Coccyx Female pelvis is broader and shallower than the male pelvis. Necessary for childbearing. Male pelvis is narrow and funnel shaped.
Coxal Bone Coxal Bone – hip bone Composed of three parts: (1) ilium (2) ischium (3) pubis The three bones join together to form the acetabulum, it receives the head of the femur and enables the thigh to rotate
Ilium Ilium-largest part of the coxal bone, can be felt at the hip. Outer edge is called the iliac crest. Ilium connects in the back with the sacrum, forming the sacroiliac joint.
Ilium Greater Sciatic Notch-site where blood vessels and the sciatic nerve pass from the pelvic cavity into the posterior thigh region. Ilium produces blood cells and is a common site for bone marrow biopsy.
Ischium Ischium-most inferior part of the coxal bone. Contains three important structures: Ischial tuberosity Ischial spine Lesser sciatic notch The ischial tuberosity is the part of the coxal bone on which you sit.
Pubis Pubis – most anterior part of the coxal bone. The two pubic bones join together in the front as the symphysis pubis. A disc of cartilage separates the pubic bones at the symphysis pubis.
Pubis Obturator Foramen- large hole formed as the pubic bone fuses with a part of the ischium. The obturator is the largest foramen in the body.
Lower Extremities The lower limb includes the bones of: The thigh The knee-cap Leg Foot
Lower Extremities Femur-the thighbone. Longest and strongest bone in the body. Articulates with the coxal bone to form the hip and with the bones of the lower leg to form the knee. The head of the femur sits in the acetabulum of the coxal bone and allows the thigh to rotate at the hip.
Lower Extremities Greater and lesser trochanters - provide sites of attachment for several muscles. Neck of the femur is the most common site of fracture in the elderly who “break hips”.
Lower Extremities Patella-kneecap Triangle bone that is located within a tendon that passes over the knee. The patella articulates with both the femur and the tibia.
Lower Extremities Tibia and Fibula- form the leg. The tibia is the shinbone and articulates with the femur at the knee. The tibia is the larger weight bearing bone of the leg. Tibial Tuberosity-site of attachment for the muscles and ligaments of the leg.
Lower Extremities Fibula-long thin bone positioned laterally alongside the tibia in the lower leg. TIB-Thick Inner Bone FibuLA-Lateral to the tibia.
Lower Extremities Foot - each foot has: Ankle Instep Five toes Great toe is called the hallux. Seven tarsal bones form the ankle. Talus articulates with the tibia and fibula.
Lower Extremities Bones of the foot: Calcaneus-heel bone, supports the body weight. Five metatarsal bones form the instep of the foot. Tarsals, metatarsals, and associated tendons and ligaments form the arches of the foot.
Joints (Articulations) Joint or articulation-the site where two bones meet. Perform two functions: (1) hold the bones together. (2) provide flexibility to a rigid skeleton.