Skeletal System Anatomy PDF

THE SKELETAL SYSTEM THE SKELETAL SYSTEM - The skeletal system has four components: bones, cartilage, tendons, and ligaments. Functions of the Bones 1. Support the bones of the legs act as pillars to support the body trunk when we stand, and the rib cage supports the thoracic wall. 2....

THE SKELETAL SYSTEM THE SKELETAL SYSTEM - The skeletal system has four components: bones, cartilage, tendons, and ligaments. Functions of the Bones 1. Support the bones of the legs act as pillars to support the body trunk when we stand, and the rib cage supports the thoracic wall. 2. Protection Bones protect soft body organs. The vertebrae surround the spinal cord, 3. Allow movement Skeletal muscles, attached to bones by tendons, use the bones as levers to move the body and its parts. 4. Storage Fat is stored in the internal (marrow) cavities of bones. Bone itself serves as a storage house for minerals, the most important of which are calcium and phosphorus. 5. Blood cell formation Blood cell formation or hematopoiesis, occurs within the marrow cavities of certain bones. Classification of Bones (based on histology) The adult bone is composed of 206 bones. There are two basic types of osseous, or bone tissue: 1. Compact bone - is dense and looks smooth and homogenous - Mostly solid matrix and cells 2. Spongy bone - has a spiky, open appearance like a sponge - Located mainly in the epiphyses of long bones - It forms the interior of all other bones - Consists of a lacy network of bone with many small, marrow-filled spaces  Bone Classification According to Shape 1. Long Bones Longer than they are wide They have a shaft with enlarged ends Mostly compact but also contains spongy bone at the ends All the bones of the limbs except, except the patella (kneecap) and the wrist and ankle bones, are long bones. 2. Flat Bones Are thin, flattened, and usually curved Most bones of the skull, the ribs, and the sternum (breastbone) are flat bones 3. Short Bones Are generally cube-shaped and contain mostly spongy bone with an outer layer of compact bone. The bones of the wrist and ankle are short bones Sesamoid bones, which forms within tendons, are a special type of short bone (patella) 4. Irregular Bones Bones that do not fit into the other three categories Vertebrae, pelvic girdle and facial bones Structure of Bone In a long bone, the diaphysis (shaft) makes up most of the bone’s length and is composed of compact bone - the diaphysis is covered and protected by a fibrous connective tissue membrane called the periosteum. - Sharpey’s fibers secure the periosteum to the underlying bone. The epiphyses are the ends of long bones. - Instead of periosteum, articular  Epiphyseal line – is a remnant of the epiphyseal plate seen in a young, growing bone. By the end of puberty, when hormones inhibit long bone growth, epiphyseal plates have been completely replaced by bone, leaving only the epiphyseal lines to mark their previous location. Endosteum – a delicate connective tissue covering the inner bony surface of the shaft  Medullary cavity - the cavity of the shaft - a storage area for red marrow, which produces blood cells Children’s bones contain red marrow until the age of 6 or 7, when it is gradually replaced by yellow marrow Yellow marrow – stores adipose (fat) tissue; less active in hematopoiesis Microscopic Anatomy Under a microscope, you can see that spongy bone is composed of small needlelike pieces of bone called trabeculae In compact bone, the mature bone cells, osteocytes, are found within the bone matrix in tiny cavities called lacunae The lacunae are arranged in concentric circles called lamellae around central canals (Haversian canals). Central canals run lengthwise through the bony matrix, carrying blood vessels and nerves to all areas of the bone.  Tiny canals, canaliculi, radiate outward from the central canals to all lacunae. The communication pathway from the outside of the bone to its interior is completed by perforating canals (Volkmann’s canals). The calcium salts deposited in the matrix give bone its hardness. The organic parts (especially the collagen fibers) provide for bone’s flexibility and great tensile strength (ability to be stretched without breaking). Bone Formation, Growth, and Remodelling The skeleton is formed from two of the strongest and most supportive tissues in the body – cartilage and bone. In embryos, the skeleton is primarily made of hyaline cartilage, but in young children, most of the cartilage has been replaced by bone (except the nose bridge, part of the ribs, and the joints). Most bones develop using hyaline cartilage structures as their “models”. This process of bone formation is called ossification. Ossification involves two major phases: 1. first, the hyaline cartilage model is completely covered with bone matrix by bone building cells called osteoblasts. 2. Then, in the fetus, the enclosed hyaline cartilage model is replaced by bone, and the center is digested away, opening up a medullary cavity within the newly formed bone. By birth or shortly after, most hyaline cartilage models have been converted to bone except for two regions – the articular cartilages (that cover the  Growing bones also widen as they legthen to maintain proper proportion. Because these two processes occur at about the same rate, the circumference of the long bone expands, and the bone widens. This process by which bones increase in diameter is called appositional growth. Bone Remodelling Bones are remodelled continually in response to changes in two factors: 1. The calcium ion level in the blood (Normal: 8.5 – 10.5 mg/dL) or (4.3 to 5.3 mEq/L) 2. The pull of gravity and muscles on the skeleton When the blood calcium ion level drops below its homeostatic level, the parathyroid glands are stimulated to release parathyroid hormone into the blood PTH activates osteoclasts, to break down bone matrix and release calcium ions into the blood. When blood calcium ion level is too high, Ca is deposited in bone matrix as hard calcium salts by osteoblasts. Homeostatic Imbalance Rickets Disease of children in which the bones fail to calcify due to a lack of Ca in the diet or lack of vit. D, which is needed to absorn Ca into the bloodstream. As a result, the bones soften. In adults, this condition is called Osteomalacia or “adult rickets”. Giantism/Gigantism is a condition of abnormally increased height that usually results from excessive cartilage and bone formation at the epiphyseal plates of long bones. Pituitary gigantism – the most common type of giantism, results from excess secretion of pituitary growth hormone. Acromegaly involves the growth of connective tissue, including bones, after the epiphyseal plates have ossified. The effect mainly involves increased diameter or thickness of bones and is most strikingly apparent in the face and hands. Many pituitary giants also develop acromegaly later in life. Dwarfism is a condition of abnormally decreased height. Pituitary dwarfism results when abnormally low levels of pituitary growth hormone affect the whole body, thus producing a small person who is normally proportioned. Achondroplasia the most common type of dwarfism caused by a mutation of a gene regulating bone growth. It results in a person with nearly normal-sized trunk and head but shorter than Bone Fractures - Are classified in many ways: 1. Open (formerly called compound) fracture Occurs when an open wound extends to the site of the fracture or when a fragment of bone protrudes through the skin. 2. Closed fracture (formerly called simple fracture) A fracture that does not perforate the skin Bone Repair Bone is a living tissue that can undergo repair following damage to it. This process has four major steps. 1. Hematoma formation  Blood vessels are ruptured when the bone breaks.  As a result, a blood-filled swelling, or bruise, called a hematoma forms. Bone cells deprived of nutrition die. 2. Callus formation  Callus is a mass of granulation tissue that forms at a fracture site, connecting the broken ends of the bone.  The callus forms as the clot dissolves and is removed by macrophages.  Capillaries grow into the tissue and phagocytic cells begin cleaning debris 3. Callus ossification  As more osteoblasts and osteoclasts migrate into the area and multiply, the fibrocartilage callus is gradually replaced by bony callus made of spongy bone.  4-6 weeks after an injury  Immobilization is critical because 4. Bone remodelling  Over the next few weeks to months, the bony callus is remodelled in response to the mechanical stresses placed on it, so that it forms a strong permanent “patch” at the fracture site.  The remodelling process may take more than a year to complete Calcium Homeostasis - Bone is the major storage site for calcium in the body - Movement of Ca into and out of the bone helps determine blood Ca levels, which is critical for normal muscle and nervous system function Two hormones regulate Ca++ levels in the blood: parathyroid hormone (PTH) and calcitonin PTH is the major regulator of blood Ca - Falling blood Ca2+ levels signal the parathyroid glands to release PTH - PTH signals * Osteoclasts to degrade bone matrix and release Ca into the blood Calcitonin - Rising blood Ca++ levels trigger the thyroid to release calcitonin - Calcitonin stimulates calcium salt deposition in bone by decreasing osteoclast activity Effects of Aging On The Skeletal System With aging, bone matrix is lost and the matrix becomes more brittle Cancellous bone loss results from a thinning and loss of trabeculae Compact bone loss mainly occurs from the inner surface of bones and involves less osteon formation Loss of bone calcium Increases the risk for fractures Causes deformity Loss of height Pain Stiffness Loss of teeth (due to loss of bone from the jaws) General Considerations of Bones  The average adult skeleton has 206 bones  Bones can be categorized as paired or unpaired Paired bones – two bones of the same type located on the right and left sides of the body Unpaired bone – bone located on the midline of the body  There are 86 paired and 34 unpaired bones  Most of the anatomical terms used to describe the features of the bones are based on the relationship between the bones and associated soft tissues.  The skeleton is divided into the axial and appendicular skeletons Axial Skeleton - The axial skeleton forms the longitudinal axis of the body. It can be divided into three parts: the skull, the vertebral column, and the thoracic cage. SKULL Bones of the head form the skull or cranium Formed by two sets of bones: cranium and facial bones All of the bones of the skull are joined together by sutures except the mandible (jawbone) Cranium The boxlike cranium is composed of eight large flat bones. Except for two sets of paired bones (parietal and temporal), they are single bones.  Frontal Bone - Forms the forehead, the bony projections under the eyebrows, and the superior part of each eye’s orbit.  Parietal Bones - The paired parietal bones form most of the superior and lateral walls of the cranium. - The sagittal suture is formed at the midline where the two parietal bones meet, and the coronal suture is formed where the parietal bones meet the frontal bone.  Temporal Bones - The temporal bones lie inferior to the parietal bones and join them at the squamous sutures. - Several important bone markings appear on the temporal bones:  External acoustic meatus is canal that leads to the eardrum and the middle ear. It is the route by which sound enters the ear.  Styloid process, a sharp, needlelike projection, is just inferior to the external auditory meatus. Many neck muscles use the styloid process as an attachment point.  Zygomatic process is a thin bridge of bone that joins with the cheekbone (zygomatic bone) anteriorly.  Mastoid process (behind the ear) is a rough projection posterior and inferior to the external acoustic meatus. It provides an attachment site for some muscles of the neck.  Jugular foramen, at the junction of the occipital and temporal bones, allows passage of the jugular vein, the largest vein of the head, which drains blood from the brain.  Occipital Bone The occipital bone is the most posterior bone of the cranium. It forms the base and back wall of the skull. The occipital bone joins the parietal bones anteriorly at the lambdoid suture. In the base of the occipital bone is a large opening, the foramen magnum which surrounds the lower part of the brain and allows the spinal cord to connect with the brain.  Sphenoid Bone - The butterfly-shaped sphenoid bone spans the width of the skull and forms part of the floor of the cranial cavity. - The sella turcica in the midline of the sphenoid forms a snug enclosure for the pituitary gland. - The foramen ovale allows fibers of cranial nerve V (the trigeminal nerve) to pass to the chewing muscles of the lower jaw.  Ethmoid Bone - It forms the roof of the nasal cavity and part of the medial walls of the orbits. Facial Bones Fourteen bones make up the face. Twelve are paired; only the mandible and vomer are single.  Maxillae - The two maxillary bones fuse to form the upper jaw. - The maxillae carry the upper teeth in the alveolar process  Palatine Bones - They form the posterior part of the hard palate - Failure of these or the palatine processes to fuse medially results in  Zygomatic Bones - Are commonly referred to as the cheekbones  Lacrimal Bones - Are fingernail-sized bones forming part of the medial wall of each orbit. - Each lacrimal bone has a groove that serves as a passageway for tears (lacrima).  Nasal Bones - The small rectangular bones forming the bridge of the nose.  Vomer Bone - The single bone in the median line of the nasal cavity - The vomer forms the inferior part of the  Inferior Nasal Conchae - Are thin, curved bones projecting medially from the lateral walls of the nasal cavity.  Mandible - The mandible, or lower jaw, is the largest and strongest bone of the face. - It joins the temporal bones on each side of the face. - The only freely movable joins in the skull. - The lower teeth lie in the alveolar process at the superior edge of the mandibular body.  The Hyoid Bone - Though not really part of the skull, the hyoid bone is closely related to the mandible and temporal bones. - It is unique in that it is the only bone of the body that does not articulate with any other bone. - Instead, it is suspended in the midneck region about 1 inch above the larynx anchored by ligaments to the styloid processes of the temporal bones. Vertebral Column Serving as the axial support of the body, the vertebral column (spine) extends from the skull to the pelvis. It is formed from 26 irregular bones connected and reinforced by ligaments in such a way that a flexible, curved structure results. Before birth, the spine consists of 33 separate bones called  The individual vertebrae are separated by pads of flexible fibrocartilage – intervertebral discs – that cushion the vertebrae and absorb shock while allowing the spine flexibility. Homeostatic Imbalance There are several types of abnormal spinal curvatures: 1. Scoliosis 2. Kyphosis 3. Lordosis The common features of vertebrae include the following: Body or centrum: disclike, weight-bearing part of the vertebra facing anteriorly in the vertebral column. Vertebral arch: arch formed from the joining of all posterior extensions, the laminae and pedicles, from the vertebral body. Vertebral foramen: canal through which the spinal cord passes. Tranverse processes: two lateral projections from the vertebral arch Spinous process: single projection arising from the posterior aspect of the vertebral arch Superior and inferior articular processes: paired projections lateral to the vertebral  Cervical Vertebrae - The seven cervical vertebrae (identified as C1 to C7) form the neck region of the spine. - The first two vertebrae (atlas and axis) are different because they perform functions not shared by other cervical vertebrae. - The atlas (C1) has no body and the superior surfaces of its transverse processes contain large depressions that receive the occipital condyles of the skull. - This joint allows you to nod “yes.” - The axis (C2) acts as a pivot for the rotation of the atlas and skull above. - It has a large process, the dens, which acts as the pivot point. - The joint between C1 and C2 allows you to rotate your head from side to side to indicate  Thoracic Vertebrae - The 12 thoracic vertebrae (T1 to T12) are all typical. - They are larger than the cervical vertebrae and are distinguished by the fact that they are the only vertebrae to articulate with the ribs. - The body is somewhat heart-shaped and has two costal facets on each side, which receive the heads of the ribs. - The transverse processes of each thoracic vertebrae articulate with the knoblike tubercles of the ribs. - The spinous process is long and hooks sharply downward, causing the vertebrae  Lumbar Vertebrae - The five lumbar vertebrae (L1 to L2) have massive, blocklike bodies that are somewhat kidney bean-shaped. - Their short, hatchet- shaped spinous processes make them look like a moose head from the lateral aspect. - Because most of the stress on the vertebral column occurs in the lumbar Sacrum - The sacrum is formed by the fusion of five vertebrae. - Superiorly it articulates with L5 and inferiorly it connects with the coccyx. - Each winglike ala articulates laterally with the hip bone, forming a sacroiliac joint. - The sacrum forms the posterior wall of the pelvis Coccyx - The coccyx is formed from the fusion of three to five tiny, irregularly shaped vertebrae. - It is the human “tailbone,” a remnant of the tail that other vertebrate animals have. Thoracic Cage The sternum, ribs, and thoracic vertebrae make up the bony thorax, routinely called the thoracic cage because it forms a protective cage of slender bones and cartilages around the organs of the thoracic cavity (heart, lungs, and major blood vessels)  Sternum (Breastbone) - Is a typical flat bone and the result of the fusion of three bones – the manubrium, body, and xiphoid process. - It is attached directly to the first seven pairs of ribs via costal cartilages. - The sternum has three important bony landmarks – the jugular notch, the sternal  The jugular notch - (concave upper border of the manubrium) can be palpated easily - Generally it is at the level of the third thoracic vertebra. The sternal angle - Results where the manubrium and body meet at a slight angle to each other, so that a transverse ridge is formed at the second level of the ribs. The xiphisternal joint - The point where the sternal body and xiphoid process fuse, lies at the level of the ninth thoracic vertebra Ribs - Twelve pairs of ribs form the walls of the bony thorax. - The true ribs, the first seven pairs, attach directly to the sternum by costal cartilages. - False ribs, the next five pairs, either attach indirectly to the sternum or are not attached to the sternum at all. - The last two pairs of false ribs lack the sternal attachments, so they are also called floating ribs. - The intercostal spaces are filled with the intercostal muscles, which aid in Appendicular Skeleton The appendicular skeleton is composed of 126 bones of the limbs (appendages) and the pectoral and pelvic girdles, which attach the limbs to the axial skeleton. Bones of the Shoulder Girdle - Each pectoral girdle, or shoulder girdle, consists of two bones – a clavicle and a scapula. - The paired clavicles, or collar bones, are slender, doubly curved bones. Each clavicle attaches to the manubrium of the sternum medially and to the scapula laterally, where it helps to form the shoulder joint. - The paired scapulae, or shoulder blades, are - Each triangular scapula has a flattened body with three borders: superior, medial (vertebral), and lateral (axillary) - It has three angles: superior, inferior, and lateral. - The glenoid cavity, is a shallow socket that receives the head of the arm bone. - The scapula has two important processes – the acromion, which is the enlarged lateral end of the spine of the scapula, and the beaklike coracoid process. - The acromion connects with the clavicle laterally at the acromioclavicular Bones of the Upper Limbs Thirty separate bones form the skeletal framework of each upper limb, including the arm, forearm, and hand. Arm The arm is formed by a single bone, the humerus, which is a typical long bone. At its proximal end is a rounded head that fits into the shallow glenoid cavity of the scapula. Immediately inferior to the head is a slight constriction called the anatomical neck. Anterolateral to the head are two bony projections separated by the intertubercular sulcus – the greater  Just distal to the tubercles is the surgical neck. It the midpoint of the shaft is a roughened area called the deltoid tuberosity, where the deltoid muscle of the shoulder attaches. At the distal end of the humerus is the medial trochlea, which looks somewhat like a spool, and the lateral ball-like capitulum. Above the trochlea anteriorly is a depression, the coronoid fossa; on the posterior surface is the olecranon fossa. These two depressions, which are flanked by the medial epicondyle and lateral epicondyle, allow the corresponding Forearm Two bones, the radius and the ulna, form the skeleton of the forearm Both proximally and distally the radius and ulna articulate at small radioulnar joints. The two bones are connected along their entire length by the flexible interosseous membrane. Both the radio and ulna have a styloid process at their distal end. When the upper limb is in the anatomical position, the ulna is the medial bone of the forearm. On its proximal end are the anterior coronoid process and the posterior olecranon, which are separated by the trochlear notch. Hand The skeleton of the hand consists of the carpals, the metacarpals, and the phalanges. The eight carpal bones, arranged in two irregular rows of four bones each, form the part of the hand called the carpus, or the wrist. The palm of the hand consists of the metacarpals. When the fist is clenched, the heads of the metacarpals become obvious as the “knuckles.” The phalanges are the bones of the fingers. Bones of the Pelvic Girdle The pelvic girdle is formed by two coxal bones (called hip bones) and the sacrum. Bearing weight is the most important function of this girdle because the total weight of the upper body rests on the  The reproductive organs, urinary bladder, and part of the large intestine lie within and are protected by the pelvis Each hip bone is formed by the fusion of three bones: Ilium  is a large, flaring bone that forms most of the hip bone.  The upper edge of an ala, the iliac crest, is an important anatomical landmark by those who give intramuscular injections. Ischium  Is the “sit down bone”, because it forms the most inferior part of the coxal bone.  The ischial tuberosity is a roughened area that receives body weight when you are sitting.  The ischial spine, superior to the tuberosity, is another important anatomical landmark in the pregnant woman, because it narrows the outlet of the pelvis through which the baby must pass during birth. Pubis  Is the most anterior and inferior part of a coxal bone.  The pubic bones of each hip bone articulate anteriorly to form a cartilaginous join, the pubic symphysis. The ilium, ischium, and pubis fuse at the deep socket called the acetabulum (vinegar cup) which receives the head of the thigh bone. The bony pelvis is divided into two regions: the false pelvis and the Differences between a male and female pelvis: The female inlet is larger and more circular The female pelvis as a whole is shallower, and the bones are lighter and thinner The female ilia flare more laterally, giving women more curvy hips The female sacrum is shorter and less curved The female ischial spines are shorter and farther apart; thus the outlet is larger The female pubic arch is more rounded because the angle of the pubic arch is greater Bones of the Lower Limbs Thigh Femur Is the only bone in the thigh It is the heaviest, strongest, and longest bone in the body Its proximal end has a ball-like head, a neck, and a greater trochanter and lesser trochanter.  The head of the femur articulates with the deep, secure socket of the acetabulum of the hip bone. The surgical neck of the femur is a common fracture site, especially in old age. Distally in the femur are the lateral condyle and medial condyle, which articulate with the tibia below. Posteriorly these condyles are separated by the deep intercondylar fossa. Anteriorly on the distal femur is the smooth patellar surface which forms a Leg Two bones, the tibia and fibula, form the skeleton of the leg. Connected along their length by an interosseous membrane. The tibia, or shinbone, is larger and more medial. At the proximal end, the medial condyle and lateral condyle articulate with the distal end of the femur to form the knee joint. Distally, a process called the medial malleolus forms the inner bulge of the ankle. The anterior surface of the tibia is a sharp ridge, the anterior border, that is unprotected by muscles; thus it is easily felt beneath the skin.  The fibula which lies alongside the tibia laterally, forms joints with it both proximally and distally, and is thin and sticklike. The fibula has no part in forming the knee joint. Its distal end, the lateral malleolus, forms the outer part of the ankle. Foot Composed of the tarsals, metatarsals, and phalanges. It supports our body weight and serves as a lever that allows us to propel our bodies forward when we walk and run. The tarsus, forming the posterior half of the foot, is composed of seven tarsal bones. Body weight is carried mostly by the two largest tarsals, the calcaneus (heel bone), and the talus (ankle). The talus lies superior to the calcaneus, articulates with the tibia, and allows pointing of the toes.  Five metatarsals form the sole, and 14 phalanges form the toes. Like the fingers of the hand, each toe has three phalanges, except the great toe, which has two. Ligaments, which bind the foot bones together, and tendons of the foot muscles help to hold the bones firmly in the arched position but still allow a certain amount of springiness. Joints Also called articulations, are the sites where two or more bones meet. They have two functions: they hold the bones together securely but also give the rigid skeleton mobility. Joints are classified in two ways: functionally and structurally. Functional classification focuses on the amount of movement the joint allows: 1. Synarthroses – immovable joints (axial skeleton) 2. Amphiarthroses – slightly movable 3. Diarthroses – freely movable (limbs)  Structurally, there are fibrous, cartilaginous, and synovial joints. Fibrous Joints  Consist of two bones that are united by fibrous connective tissue, have no joint cavity, and exhibit a little or no movement.  Joints in this group are classified further as: Sutures (coronal, lambdoid, sagittal, squamous) Syndesmoses (radioulnar, tibiofibular, stylomandibular, stylohyoid) Gomphoses (dentoalveolar – tooth and alveolar process) Cartilaginous Joints Come in two varieties: 1. Synchondroses  immovable joints linked by hyaline cartilage  The joints between the ilium, ischium, and pubis before those bones fuse together are examples of synchondroses joints. 2. Symphyses  Are amphiarthrotic (slightly movable) joints linked by discs of fibrocartilage.  Examples include the intervertebral discs of the spinal column, and the pubic symphysis of the pelvis Synovial Joints Are joints in which the articulating bone ends are separated by a joint cavity containing synovial fluid. All joints of the limbs are synovial joints. All synovial joints have four distinguishing features: 1. Articular cartilage – covers the ends of the bones forming the joint 2. Articular capsule – the joint surfaces are enclosed by a sleeve, or layer, of fibrous connective tissue, which is lined with a smooth synovial membrane. 3. Joint cavity – contains lubricating synovial fluid secreted by the synovial membrane 4. Reinforcing ligaments – the fibrous layer of the capsule is usually reinforced with ligaments.  Bursae (purses) are flattened fibrous sacs lined with synovial membrane and containing a thin film of synovial fluid Bursae are common where ligaments, muscles, skin, tendons, or bones rub together. A tendon sheath is essentially an elongated bursa that wraps completely around a tendon subjected to friction, like a bun around a hot dog. Types of Synovial Joints Based on Shape 1. Plane/Gliding Joint - Consist of two opposed flat surfaces of about equal size in which a slight amount of gliding motion can occur between the bones. - Ex. Articular processes between vertebrae 2. Hinge Joint - Consist of a convex cylinder in one bone applied to a corresponding concavity in the other bone - Ex. Elbow and knee joints 3. Pivot Joint - Consists of a relatively cylindrical bony process that rotates within a ring composed partly of bone and partly of ligament - Ex. The articulation between the head of the radius and the proximal end of the ulna 4. Saddle Joint - Consist of two saddle-shaped articulating surfaces oriented at right angles to each other so that complimentary surfaces articulate with each other. - Ex. Carpometacarpal joint, metacarpal of the thumb 5. Ball-and-Socket Joint - Consist of a ball (head) at the end of one bone and a socket in an adjacent bone into which a portion of the ball fits - Ex. Shoulder and hip joints Angular Movements 1. Flexion Is the movement of a body part anterior to the coronal plane, or in the anterior direction The literal definition for flexion is to bend 2. Extension Is the movement of a body part posterior to the coronal plane, or in the posterior direction Extension is to straighten 3. Abduction (to take away) Is movement away from the median plane (midline of the body) 4. Adduction (to bring together) Movement toward the body Circular Movements 1. Rotation Is the turning of a structure around its long axis, such as the movement of the atlas around the axis when shaking the head “no” Medial rotation vs. lateral rotation 2. Pronation and Supination Refer to the unique rotation of the forearm. 3. Circumduction Is a combination of flexion, extension, abduction, and adduction Special Movements 1. Elevation and Depression Moving a structure superiorly or inferiorly Depression of the mandible opens the mouth, and elevation closes it. 2. Protraction and Retraction Protraction consists of moving a structure in a gliding motion in an anterior direction Retraction moves the structure back to the anatomical position or even more posteriorly 3. Excursion Lateral excursion is moving the mandible to either the right or left of the midline such as, grinding the teeth or chewing Medial excursion returns the mandible to the neutral position 4. Opposition and Reposition Opposition is a unique movement of the thumb and little finger 5. Inversion and Eversion Inversion of the foot consists of turning the ankle so that the plantar surface of the foot faces laterally Developmental Aspects of the Skeleton Birth to Adulthood The first “long bones” in the very young fetus are formed of hyaline cartilage, and the earliest “flat bones” of the skull are actually fibrous membranes. The fibrous membranes connecting the cranial bones are called fontanels. The largest fontanel is the diamond- shaped anterior fontanel. The fontanels usually fully ossify by 2  During puberty, the female pelvis broadens in preparation for childbearing, and the entire male skeleton becomes more robust. By the end of adolescence, the epiphyseal plates of long bones that provide for longitudinal growth in childhood have become fully ossified, and long-bone growth ends. Once adult height is reached, a healthy skeleton changes very little until late middle age. Older Adults When we remain active physically and muscles and gravity pull on the skeleton, the bones respond by becoming stronger. By contrast, if we are totally inactive, they become thin and fragile. Estrogen helps to maintain the health and normal density of a woman’s skeleton. Menopause is strongly implicated as a cause of osteoporosis. Other factors that may contribute to osteoporosis are a diet poor in calcium and protein, lack of vitamin D, smoking, and insufficient weight-bearing exercise to stress the bones.