The primary organ of the Skeletal System Forms most of the skeleton Remarkably strong but light weight and is dynamic
Support: bone provides a framework for the body by supporting soft tissues and providing points of attachment for many skeletal muscles. Protection: bones protect many internal organs from injury. Movement: skeletal muscles attach to bones. When muscles contract, they pull on bones and together they produce movement. Mineral homeostasis: bone tissue stores several minerals, especially calcium and phosphorus, which are important in muscle contraction and nerve activity. On demand, bone releases minerals into the blood to maintain critical mineral balances and to distribute them to other parts of the body. Site of blood cell production: within certain parts of bones, a connective tissue called the red marrow produces blood cells, a process called hemopoiesis. Red bone marrow – one type of bone marrow which consists of blood cells in immature stages, adipose cells, and macrophages – it produces red blood cells, white blood cells and platelets. Storage of energy: Lipids stored in cells of a second type of bone marrow called the yellow marrow. Yellow marrow – consists primarily of adipose cells, and is an important chemical energy reserve.
Diaphysis (dia = through; physis = growth) – the shaft or long, main portion of the bone. Epiphyses (epi = above; physis = growth) – the extremities or ends of the bone. Metaphysis – region in a mature bone where the diaphysis joins the epiphysis. In a growing bone, it is the region that includes the epiphyseal plate where cartilage is replaced by bone. Articular Cartilage – a thin layer of hyaline cartilage covering the epiphysis where that bone forms a joint with another bone. The cartilage reduces friction and absorbs shock at freely movable joints. Periosteum (peri=around; osteo=bone) is the membrane around the surface of the bone not covered by articular cartilage. Medullary cavity – is the space within the diaphysis that contains the fatty yellow marrow. Endosteum – it is the membrane that contains Osteoprogenitor cells that lines the medullary cavity.
Osteoprogenitor cells (osteo=bone; pro=precursor; gen = to produce) are unspecialized cells derived from mesenchyme, the tissue from which all connective tissues are derived. They are found in the inner portion of the periosteum, in the endosteum, and in canals in bone that contain blood vessels. Osteoblasts (blast = germ or bud) are cells that form bone, but they have lost the ability to divide by mitosis. They secrete collagen and other organic components needed to build bone tissue. Osteocytes (cyte = cell) are mature bone cells that are derived from osteoblasts; they are the principal cells of bone tissue. Osteoclasts (clast = to break) are cells believed to be developed from circulating monocytes. They settle on the surface of bone and function in bone resorption (destruction of matrix), which is important in the development, growth, maintenance, and repair of bone.
It is the placement of old bone tissue by new bone tissue Old bone is constantly destroyed by osteoclasts, whereas new bone is constructed by osteoblasts Remodeling requires minerals (calcium, phosphorus, magnesium, and manganese), vitamins (D, C, A, and B12), and hormones (human growth hormone, sex hormone, insulin, thyroid hormones, parathyroid hormone, and calcitonin)
Long Bones: Have greater length than width and consist of a shaft and a variable number of ends. They are slightly curved for strength A curved bone absorbs the stress of the body weight at several different points so the stress is evenly distributed. If such bones were straight, the weight of the body would be unevenly distributed and the bone would easily fracture. Long bones consist mostly of compact bone, which is dense and has few spaces. Long bones include those in the thigh (femur), leg (tibia and fibula), toes and fingers (phalanges), arms (humerus), and forearm (ulna and radius).
Short Bones: Are somewhat cube-shaped and nearly equal in length and width. They are spongy bone except at the surface, where there is a thin layer of compact bone. Examples of short bones are the wrist (carpal) and ankle (tarsal) bones. Flat Bones: Flat bones are generally thin and composed of two nearly parallel plates of compact bone enclosing a layer of spongy bones. Flat bones can give considerable protection and provide extensive areas for muscle attachment. Flat bones includes the cranial bones (which protects the brain), breast bone (sternum) and ribs (which protects organs in the thorax) Irregular Bones: They consist of thin layers of compact bone surrounding a spongy interior. As implied by the name, their shapes are irregular and complicated. Such bones includes the backbones (vertebrae)
The adult human skeleton consists of 206 named bones grouped into two (2) principal divisions: the axial skeleton and the appendicular skeleton.
Forms the longitudinal axis of the body and is divided into three (3) parts: the Skull, the Vertebral Column, and the Bony Thorax.
The Skull The skull contains 22 bones The skull rests on the superior end of the vertebral column The skull is divided into Cranial and Facial bones
The Skull form the cranial cavity and enclose and protects the brain Includes frontal bone, parietal bones (2), temporal bones (2), occipital bone, sphenoid bone, and ethmoid bone.
The Skull Frontal Bone – forms the forehead, the bony projections under the eyebrows, and the superior part of each eye’s orbit. Parietal Bones – paired bones that form most of the superior and lateral walls of the cranium; they meet in the midline of the skull at the sagittal suture and form the coronal suture where they meet the frontal bone.
The Skull Temporal Bones – paired bones that lies inferior to the parietal bones; they join them at the squamous sutures; several important bone markings appear on the temporal bone: External Auditory meatus – a canal that leads to the eardrum and the middle ear. Styloid process – a sharp, needle-like projection, just inferior to the external auditory meatus, used as attachment point of several neck muscles. Zygomatic Process – a thin bridge of bone that joins with the cheek bone (zygomatic bone) anteriorly. Mastoid Process – a rough pojection posterior and inferior to the expternal auditory meatus, which is full of air cavities (mastoid sinuses); it provides an attachment site for some muscles of the neck. Jugular Foramen – located at the junction of the occipital and temporal bones, allows tha passage of the jugular vein of the head, which drains deoxygenated blood from the bain.
The Skull Occipital Bone – is the most posterior bone of the cranium; it forms the floor and back wall of the skull; it joins the parietal bones anteriorly at the lamboid suture Foramen Magnum – a large opening at the base of the occipital bone which surrounds the lower part of the brain and allows the spinal chord to connect with the brain. Occypital Condyles – are rocker-like projections located at the lateral sides of the foramen magnum, which rest on the first vertebra of the spinal column.
The Skull Sphenoid Bone – a butterfly-shaped bone which spans the width of the skull and forms part of the floor of the cranial cavity. Optic Foramen – allows the optic nerve to pass to the eyes Ethmoid Bone – an irregularly shaped bone that lies anterior to the sphenoid bone; it forms the roof of the nasal cavity and part of the medial walls of the orbits.
The SkullFacial Bones: Bones that makes up the face Includes nasal bones (2), maxillae (2), zygomatic bones (2), mandible, lacrimal bones (2), palatine bones (2), inferior nasal conchae (2), and vomer.
Facial Bones: The Skull Maxillae – two bones that fuse to form the upper jaw; all facial bones except the mandible join the maxillae; thus they are the main, or ―keystone‖, bones of the face; it carries the upper teeth on the alveolar margin; maxillae contains paranasal sinuses which drains into the nasal passages, these sinuses lightens the skull bones and probably act to amplify the sounds we make as we speak. Pallatine Bones – are paired bones that lie posterior to the palatine processess of the maxillae; they form the superior part of the hard palate. Failure of the palatine to fuse medially results in cleft palate. Zygomatic Bones – are commonly refered to as the cheekbones; they also form a good-sized portion of the lateral walls of the orbits, or eye sockets. Lacrimal Bones – are fingernail-size bones froming part of the medial walls of each orbit; each lacrimal bone has a groove that serves as a passageway for tears (lacrima = tear) Nasal Bones – are small irregular bones forming the bridge of the nose. Vomer Bone – a single bone in the median line of the nasal cavity which forms most of the nasal septum. Inferior Nasal Conchae – are thin curved bones projecting from the lateral walls of the nasal cavity.
Facial Bones: The Skull Mandible – also known as the lower jaw, is the largest and strongest bone of the face; it joins the temporal bones on each side of the face, froming the only freely movable joints in the skull; the horizontal part of the mandible (the body) forms the chin; it also holds the lower teeth in the alveolar margin at the superior edge of the mandibular body.
The Hyoid Bone Not really part of the skull but is closely related to the mandible and temporal bones It is the only bone of the body that does not articulate directly with any other bone, instead, it is suspended in the midneck region about 2cm (1 inch) above the larynx, where it is anchored by ligaments to the styloid process of the temporal bones. It is a horseshoe-shaped that serves as a movable base for the tongue and an attachment point for neck muscles that raise and lower the larynx when we swallow and speak.
The Fetal Skull The infants face is very small compared to the size of its cranium, but the skull as a whole is Fontanels: large compared to the infant’s total body Allows the fetal skull to be length – the adult skull represents only one- compressed slightly during birth eight of the total body legnth, whereas that of a newborn infant is one-fourth as long as its Its flexibility allows the infant’s entire body. brain to grow during the later part Infant’s skeleton at birth is still unfinished – of pregnancy ad early infancy some areas of hyaline cartillage still remain to The fontanels are gradually be ossified (or converted to bone). Newborn’s skull has fibrous regions (that have converted to bone during the early yet to be converted to bone), which connects part of infancy and can no longer be the cranial bones – these fibrous regions are felt by 22 to 24 months after birth. called fontanels.
Serves as the axial support of the body that extends from the skull – which it supports, to the pelvis – where it transmits the weight of the body to the lower limbs. The spine is formed from 26 irregular bones connected and reinforced by ligaments in such a way that a flexible, curved structure results. Vertebral column surrounds and protects the delicate spinal chord. Before birth, the spine consists of 33 separate bones called vertebrae, but 9 of these eventually fuse to form the composite bones, the sacrum and the coccyx, that construct the inferior portion of the vertebral column. Each single vertebrae is separated by pads of flexible fibrocartilage called, Intevertebral discs, which cushion the vertebrae and absorb shocks while allowing the spine flexibility.
Vertebrae in each regions of the spine has different characteristics but they all have similar sturctural pattern. Body or Centrum: the disclike, weight-bearing part of th vertebra facing anteriorly in the vertebral column. Vertebral Arch: arch fromed from the joining of all posterior extensions, the laminae and pedicles, from the vertebral body. Vertebral Foramen: the canal through which the spinal chord passes. Transverse Process: two lateral projections from the vertebral arch. Spinous Process: a single projection arising from the posterior aspect of the vertebral arch (actually the fused laminae) Superior and Inferior Articular Processes: paired projections lateral to the vertebral foramen, allowing a vertebra to form joints with adjacent vertebrae.
The 24 single bones of the spine aredivided into three (3) regions, thecervical vertebrae (7 vertebrae of theneck), thoracic vertebrae (the next12), and lumbar vertebrae (theremaining 5 that supports the lowerback).
The Cervical Vertebrae (C1 – C7): The seven cervical vertebrae (identified as C1 to C7) form the neck region. The frist two vertebrae (atlas and axis) are different because they perform functions not shared by the other cervical vertebrae. Atlas (C1): it has no body; the superior surfaces of its transverse process contain large depressions that receive the occipital condyles of the skull – this joint allows you to nod ―yes‖. Axis (C2): acts as a pivot for the rotation of the atlas (and skull) above; it has a large upright 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 ―no‖. The typical cervical vertebrae (C3 through C7) are the smallest, lightest vertebrae and most often, their spinous process are short and divided into two branches.
Thoracic Vertebrae (T1 to T12): Are larger than the cervical vertebrae Its body is somewhat heart-shaped and has two costal facets (articulating surfaces) on each side, which receive the heads of the ribs Its spinous process is long and hooks sharply downward, causing the vertebra to look like a giraffe’s head viewed from the side.
Lumbar Vertebrae (L1 to L5): Have a massive blocklike bodies Their short, hatchet-shaped spinous process make them look like a moose head from the lateral aspect. They are the sturdiest of the vertebrae.
Sacrum: The sacrum is formed by the fusion of five vertebrae. Superiorly it articulates with L5, and inferiorly it connects with the coccyx Sacrum forms the posterior wall of the pelvis Alae - winglike projection that articulate laterally with the hip bones, forming the sacroiliac joints. Median sacral crest – roughened midline posterior surface which is a fusion of spinous process of the sacral vertebrae. Sacral canal – the continuation of vertebral canal in the sacrum and teminates in a large inferior opening – the sacral hiatus.Coccyx: Coccyx is formed by the fusion of four tiny, irregularly shaped vertebrae. It is the human ―tailbone‖ – a remnant of the tail that other vertebrate animals have.
The bony thorax is composed of the sternum, ribs, and thoracic vertebrae. It is often called the thoracic cage because it forms a protective cage of slender bones around the ogans of the thoracic cavity (heart, lungs, and major blood vessels).
Sternum (Breastbone): The sternum is a typical flat bone which is the result of fusion of three bones – the manubrium, body, and xiphoid process. Because the sternum is so close to the body surface, it is usually the site to obtain samples of blood forming tissue for the diagnosis of suspected blood diseases. (Sternal puncture). It is where the first seven pairs of ribs are attached. Jugular notch – concave upper border of the manubrium that can be palpated easily. Sternal angle – where the manubrium and body meet at a slight angle to each other, so that a transverse ridge is formed at the level of the second ribs; it provides a handy reference point for counting ribs to locate the second intercostal space for listening to certain heart waves. Xiphisternal joint – the point where the sternal body and xiphoid process fuse; it lies at the level of teh ninth thoracic vertebra.
RIBS: 12 pairs of ribs form the walls of the bony thorax. All the ribs articulate with the vertebral column posteriorly and then curve downward and toward the anterior body surface. True ribs: the first sseven pairs of ribs that are directly attached to the sternum by costal cartilages. False ribs: that next five pairs of ribs that are either attached indrirectly to the sternum or are not attached to the sternum at all. Floating ribs: are false ribs that lack the sternal attachment.
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.
Each pectoral girdle consists of two bones – a clavicle and a scapula. The shoulder girdle is very light and allows the upper limb to have exceptionally free movement. The shoulder girdle is very easily dislocated.
Clavicle (Collar Bone): It is a slender, doubly curved bone. It attaches the manubrium of the sternum medially (at its sternal end) and to the scapula laterally, where it helps to form the shoulder joint (at its acromial end) It acts as a brace to hold the arm away from the top of the thorax and helps prevent shoulder dislocation When the clavicle is broken, the whole shoulder region caves in medially.
Scapulae (Shoulder Blades): Are triangular and are commonly called ―wings‖ because they flare when we move our arms posteriorly. It is not directly attached to the axila skeleton; it is loosely held in place by trunk muscles. The scapula has three borders – superior border, medial (vertebral) border, and lateral (axillary) border. Important markings: Acromion – the enlarged end of the spine of the scapula; it connects with the clavicle laterally at the acromioclavicular joint. Coracoid process – points over the top of the shoulder and anchors some of the muscles of the arm. Suprascapular notch – serves as a nerve passageway. Glenoid cavity – a shallow socket that receives the head of the arm bone located at the lateral angle.
Each upper limb is composed of thirty separate bones They form the foundations of the arm, forearm, and hand.
Arm: It is formed by a single bone, the humerus. Humerus is a typical long bone At its proximal end is a rounded head that fits into the shallow glenoid cavity of the scapula. Important markings: Greater and lesser tubercles – are sites of muscle attachments Deltoid tuberosity – where the large, fleshy deltoid muscle of the shoulder attaches. Trochlea and Capitulum – these processes articulates with bone of the forearm
Forearm: Formed by two bones, the radius and the ulna. Radius – the lateral bone, that is, on the thumb side of the forearm; when the hand is rotated so that the palm faces backward, the distal end of the radius crosses over and ends up medial to the ulna Ulna – is the medial bone (on the little finger side) of the forearm
Hand: The skeleton of the hand consists of the carpals, the metacarpals, and the phalanges Carpal Bones – are arranged in two irregular rows of four bones each, forms the part of the hand called the carpus (wrist); they are bound by ligaments that restrict movement between them. Metacarpals – forms the palm of the hand; they are numbered 1 to 5 from the thumb side of the hand toward the little finger; when the fist is clenched, the heads of the metacarpals become obvious as the ―knuckles‖. Phalanges – are the bones of the fingers; each hand contains 14 phalanges; there are three phalanges in each finger (proximal, middle, and distal), except in the thumb, which has only two (proximal and distal).
The pelvic girdle is formed by two coxal bones, or ossa coxae, commonly called hip bones. Together with the sacrum and the coccyx, the hips bones form the bony pelvis. The bones of the pelvic girdles are large and heavy, and they are attached securely to the axial skeleton. Each hipbone is formed by the fusion of three bones: the illium, ischium, and pubis.
Illium: Connects posteriorly with the sacrum at the sacroiliac joint It is a large, flaring bone that forms most of the hip bone. Important markings are: Alae – the winglike portion of the ilia Iliac crest – the upper edge of the alae
Ischium: It is the ―sit-down bone‖, since it forms he most inferior part of the coxal bone. Important markings are: Ischial tuberosity – is a roughened area that receives body weight when your are sitting. Ischial spine – important anatomcal landmard, particuarly in the pregnant women, because it narrows the outlet of the pelvis through which the baby must pass during the birth process. Greater sciatic notch – allows blood vessels and the large sciatic nerve to pass from the pelvis posteriorly into the thigh.
Pubis (Pubic Bone): Is the most anterior part of the coxal bone Important markings are: Obturator foramen – an opening that allows blood vessels and neves to pass into the anterior part of the thigh. Pubis symphysis – a cartilaginous joint resulted from the fusion of two pubic bones of the hip. Acetabulum – where the ilium, schium, and pubis are fused together; it receives the head of the thigh bone.
Differences Between The 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 sacrum is shorter and less curved The female ischial spines are shorter and farther apart, thus the outlet is larger The female pubic arc is more rounded because the angle of the pubic arc is greater. Female Male
It carry out our total body weight when we are erect The bones of the lower limbs are much thicker and stronger than the comparable bones of the upper limb It is composed by the bones of the thigh, leg, and foot)
Thigh Bone: Composed of a single bone, the femur. Femur is the longest, heaviest, and strongest bone in the body; it slants medially as it runs downward to join with the leg bones—this brings the knees in line with the body’s center of gravity. Important markings are: ▪ Gluteal tuberosity – along with the trochanters and intertrochanteric crest located on the shaft, serves as site for muscle attachment. ▪ Lateral and Medial condyles – articulates with the tibia below.
Leg: Formed by the two bones, the tibia and fibula, connected along their length by an interosseous membrane. Tibia (shinbone) – lager and more medial ▪ Medial and lateral condyles – articualate with the distal end of the femur to form the knee joint. ▪ Medial malleolus – forms the inner bulge of the ankle ▪ Anterior Crest (border) – a sharp ridge anterior surface of the tibia which is unprotected by muscles, thus, it is easily felt beneath the skin. Fibula – lies alongside the tibia; it has no part in forming the knee joint. ▪ 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. Tarsus – composed of seven tarsal bones that form the half of the foot. Metatarsals – forms the sole Phalanges – forms the toes
Also called articulations They hold the bones together securely and also give the rigid skeleton mobility.
CLASSIFICATION OF JOINTS CLASSIFICATION BY FUNCTION CLASSIFICATION BY STRUCTURE(Based On The Amount Of Movement (Based On Whether Fibrous Tissue, Allowed By The Joint) Cartilage, Or A Joint Cavity Separates The Bones) Synarthroses – Fibrous joints – are joints immovable joints (i.e. united by fibrous tissues (i.e. joints of the cranium) sutures of the skull); syndesmoses Amphiarthroses – Cartilaginous joints – are joints slightly movable joints connected y cartilages and are (i.e. some joints in the slightly movable spinal column) (amphiarthrotic); examples are the pubic symphysis of the Diarthroses – freely pelvis and the intervertebral movable joints (i.e. joints of the spinal column. joints of the limbs) Synovial joints – are those in which the articulating bone ends are separated by a joint cavity containing synovial fluid.
SYNOVIAL JOINTS SYNOVIAL JOINTS Has Four Distinguishing Features: Articular Cartilage: articular (hyaline) cartilage covers the ends of the bones forming the joint Fibrous Articular Capsule: are capsule of fibrous connective tissue line with a smooth synovial membrane (the reason these joint are called synovial joints) that enclose the joint surfaces. Joint Cavity: the cavity which contains lubricating fluid which is enclosed by the articular capsule. Ligaments: reinforcing the fibrous capsule.
SYNOVIAL JOINTSTypes Of SYNOVIAL JOINTS: Plane Joint: the articular surfaces are essentially flat, and only short slipping of gliding movements are allowed; gliding does not involve rotation around any axis (nonaxial movement), best examples are the intercarpal joints of the wrist.
SYNOVIAL JOINTSTypes Of SYNOVIAL JOINTS: Hinge Joint: the cylindrical end of one bone fits into a trough- shaped surface on another bone; angular movement is allowed in just one plane; hinge joints are classified as uniaxial (―one axis‖ movement); best examples are the elbow joint, ankle joint, and the joints between phalanges of the fingers.
SYNOVIAL JOINTSTypes Of SYNOVIAL JOINTS: Pivot Joint: the rounded end of one bone fits into a sleeve or ring of bone (and possibly ligaments); the rotating bone can turn only around its long axis, thus, pivot joints are also classified as uniaxial joint; best examples are the proximal radioulnar joint and the joint between the atlas and the dens of the axis.
SYNOVIAL JOINTSTypes Of SYNOVIAL JOINTS: Condyloid (“knucklelike) Joint: the egg-shaped articular surface of one bone fits into an oval concavity in another; it allow the moving bone to move (1) from side to side and (2) back and forth, but the bone cannot rotate around its long axis (movement occurs around two axes, hence these joints are biaxial); best example is the knuckle (metacarpophalangeal) joints.
SYNOVIAL JOINTSTypes Of SYNOVIAL JOINTS: Saddle Joint: each articular surface has both convex and concave areas, like a saddle; it allows essentially the same movements as condyloid joint (biaxial); the best examples are the carpometacarpal joints in the thumb.
SYNOVIAL JOINTSTypes Of SYNOVIAL JOINTS: Ball-and-Socket Joint: the spherical head of one bone fits into a round socket in another; it allow movement in all axes including rotation (multiaxial), and are the most freely moving synovial joints; best examples are the shoulder joints and the hip joints.