Functions of the Skeletal system: It manages

mineral homeostasis of calcium & phosphorus by being a storage reserve for those minerals

Functions of the Skeletal system: It houses

the site of blood cell production in the red marrow

Functions of the Skeletal system: It stores

energy in the yellow marrow

Anatomy of the Skeletal System: It is composed of

connective tissues - cartilage, osseous (bone), marrow, and periosteum

Anatomy of the Skeletal System: It is also composed of

widely separated cells (osteocytes) surrounded by a large mineral matrix consisting of hydroxyapatite and calcium carbonate which confers the hardness of bone deposited in a framework of collagen fibers which provide the tensile strength of bone. The minerals as deposited by ossification or mineralization

Hydroxyapatite

calcium, phosphorus complex

Compact Bone (Types of bones):

forms the outer layer of all bone being dense and organized into osteons to provide distribution of nutrients and the removal of wastes from the widely dispersed osteocytes providing protection, support, and resistance to stress

Spongy (cancellous) Bone (Types of bones):

forms the internal layers of most bones lacking osteon organization consisting of trabeculae surrounding spaces filled with red marrow; forms the majority of the structure of short, flat, and irregular bones as well as the epiphysis (ends) of the long bones but is totally lacking in the clavicle. It provides location of blood cell production and disperses impact energy through the skeleton

Long Bone Components (Types of bones):

diaphysis (shaft), epiphysis (ends), metaphysis (transitional area between), articular cartilage (covering the epiphysis), periosteum (outer covering of the bone, medullary (marrow) cavity, & endosteum (internal lining of marrow cavities

Bone Shapes (Types of bones):

Long(e.g. femur, radius, humerus), short (e.g. carpels), flat (e.g. frontal, parietal), irregular (e.g. vertebrae), sesamoid (e.g. patella)

Formation of bone: It replaces

pre-existing connective tissues through ossification beginning during the 6th to 7th week of embryonic life and continues to occur throughout life - dynamic system of bone replacement is continuous

Formation of bone: Ossification consists of two types:

Intramembranous and endochondral (intracartilanginous)

Formation of bone: Intramembranous

is where bone replaces fibrous membranes (e.g. flat bones of the skull)

Formation of bone: Endochondral

is where the framework is originally laid down as hyline cartilage and replaced by bone (e.g. long bones) accounting for the development of the medullary cavity by the degeration of the cartilage

Bones Lengthen from:

the epiphyseal plate which consists of 4 zones of activity

Zone 1

zone of resting cartilage

Zone 2

zone where the cartilage is dividing (proliferating)

Zone 3

zone where the cartilage has stopped growing (hypertrophic)

Zone 4

zone where the cartilage is being replaced by minerals (calcification)

Bones grow in

diameter from the periosteum where the osteoblasts respond to stress depositing additional minerals and promoting the formation of more collagen

Throughout the life, the bone is

remolded as old bone is replaced with new.

Old bone is broken down

by osteoclasts

New bone formed

by osteoblasts.

This activity is dependent on the presence of

minerals - calcium, phosphorus, magnesium, manganese & zinc; vitamins - A, B12, C, & D; hormones - human growth hormone, insulin, thyroid hormones, parathyroid hormone, and calcitonin

Moderate exercise stimulates

bone remoldeling by producing mechanical stress which promotes increased production of collagen and increase mineral deposition while lack of exercise results in demineralization and reduction of collagen

Bone repair occurs

following breaks (fractures)

Stepwise Process of Bone Repair: STEP 1

since blood vessels surrounding or within the blood are broken a clot is formed - fracture hematoma usually in the first 12 hours following the break

Stepwise Process of Bone Repair: STEP 2

over the next 24 to 48 hours fibroblasts move into the site and triggering the osteoclasts to develop which begins the formation of collagen to stabilize the fracture site forming a procallus in a process call granulation

Stepwise Process of Bone Repair: STEP 3

as the site stabilizes and more fibrous tissues and cartilage are formed and the older damage is broken down a sift callus is formed

Stepwise Process of Bone Repair: STEP 4

the fibrocartilage is gradually mineralized into spongy bone (usually 4-6 weeks) by mineralization

Stepwise Process of Bone Repair: STEP 5

the fracture site remodels itself slowly into a near original form over several months and years

The skeleton acts as a mineral reservoir for

calcium which is important to cardiac function, nerve transmission, enzymatic activity and blood function

Blood levels of calcium are

regulated by 2 hormones parathyroid hormone which raises the serum calcium levels by triggering demineralization of bone and calcitonin which reduces serum calcium levels by triggering increased mineralization of bone

Aging effects the

skeletal system by altering the hardness of bone due to demineralization leading to shrinking of the body (osterporosis) and a reduction of tensile strength which embrittles the bone leading to fractures. There result from reduction of protein intake and reduction of activity

Axial Skeleton is composed of

80 long, short, flat, and irregular bones arranged along the longitudinal axis of the body organized into the skull, hyoid, vertebral column, sternum and ribs

Skull

composed of 22 bones divided into 2 sub divisions: cranium and facial. Four of these bones contain cavities which lighten the skull, warm, filter, and moisten the air we breath or insulate the brain called the paranasal sinuses: (frontal and maxillary are open to the nasal passages and the sphenoid and ethmoid are closed to the nasal passages

Bones of the skull

articulate with one another through sutures composed of a thin layer of fibrous connective tissue creating an immovable (synarthosis) articulation

Cranium

composed of 8 bones: frontal, parietal(2), temporal (2), occipital, sphenoid, and ethmoid articulated together by 4 sutures: frontal (coronal), sagittal, lambdoid, and squamous. in the fetus and infants these sutures are not fully formed and the space is filled by a fibrous membrane called fontanels which create the soft spots in the skull. These allow the skull to flex during the birth process and the brain to grow. These become completely ossified around the age of 6-10 years old

Facial

composed of 14 bones: nasal(2), maxillae (2), zygomatic (2), lacrimal (2), palatine (2), inferior nasal conchae (2), vomer, and mandible. These are joined together by sutures with the exception of the mandible which is articulated with the temporal bone of the skull by a freely movable articulation - the temporomandibular joint

Mandible

articulates with the temporal bone of the cranium in the mandibular fossa creating the temporomandibular joint

Orbit of the skull is formed by

7 bones from both the facial and cranium:frontal ethmoid, sphenoid, and temporal of the cranium and lacrimal, nasal, and zygomatic of the facial

Hyoid

U-shaped bone located in the neck region which is suspended in musculature and does not articulate with any other bone. It supports the tongue through muscle attachment to the styloid process on the temporal bone and the upper vertebra

Vertebral Column

composed of 28 bones divided into 5 regions with intervertebral disks composed of fibrocartilage forming symphysis (amphiarthrosis) which are slightly mobile articulations. The column is divided into 2 primary curves which are present at birth (thoracic and sacral) and 2 which develop after birth which are secondary curves (cervical and lumbar).

Cervical vertebra

consists of 7 vertebrae with each having foramenia in the transverse processes.

C1 (atlas)

is highly modified lacking a centrum (body), reduced spinous process and highly curved superior articulating surfaces which articulate with the occipital condyles on the skull

C2 (axis)

is modified to a lesser extent with an elongated centrum which has a process called the dens (odontoid process) which articulates with the atlas permitting lateral movement of the skull

C3-7

are more typical vertebra

Thoracic vertebra

consists of 12 vertebrae which articulate with each other and with the 12 pair of ribs forming the thoracic cage with the sternum. The transverse processes have smooth polished areas (costal facets) which articulate with the costal tuberosity of the ribs and demifacets on the centrum where the head of the rib articulate

Lumbar vertebra

consists of 5 robust vertebrae which have enlarged centrum, shortened and heavy transverse and spinus processes

Sacrum

consists of 5 fused vertebral segments which form the pelvic girdle of the lower appendicular skeleton at the sacroiliac joint

Coccyx

usually consisting of 4 segments with only the centrum remaining and frequently fused

Thorax

torso or chest region of the body consisting of 37 bony components which protect the heart, lungs, and liver primarily and forms the upper appendicular (pectoral) girdle with the clavicle. The first 7 pair of ribs connect directly to the sternum through hyaline cartilage while 8,9&10 connect to the sternum through the hyaline cartilage of 7 and the last 2 pair are not attached to the sternum

Appendicular Skeleton

composed of 126 bones distributed into the upper and lower appendages and their girdles attached to the axial skeleton

Pectoral girdle

consists of 4 bones (clavicle (2) and (2) scapula) which articulate with the humerus in a ball and socket joint at the shoulder and with the manubrium of the sternum

Upper Appendages -

consists of 60 bones divided into a right and left appendage: upper arm (humerus), forearm (radius on the thumb (lateral) side and the ulna on the small digit (medial) side), 8 carpals in each wrist, 5 metacarpals in the palm of the hand, and 14 phalanges in the fingers (only 2 are in the thumb - pollux)

Pelvic Girdle

composed of 2 coxa each fused of 3 bony elements (ilium, ischium, and pubis) which is attached to the sacrum forming the pelvis. this is attached to the appendages by the ball and socket articulation between the acetabulum and the femur.

The pelvis is divided into 2 regions:

the true pelvis and false pelvis. It is anteriorly joined by the symphysis consisting of the pubic ramus attached to each other by a fibrocartilage disk

The pelvis differs with

gender with the male pubic (pelvic) angle is about 90 degrees and the female's is 110 degrees or more

Lower Appendages

consists of 60 bones with 2 femur (upper leg - thigh), 2 patella (knee cap), 2 tibia (large bone of the lower leg - shin), 2 fibula (thinner bone of the lower leg on the lateral side), 7 tarsal bones (forming the ankle, heel, and posterior foot) 5 metatarsels (forming the arch of the foot) and 14 phalanges (2 in the great toe - hallux)

Articulations

any area where contact occurs between bones with there structure determining the type of movement of the joint (articulation)

Synarthosis (immovable articulations)

these joints are rigid, lack a synovial cavity, and are held together by either fibrous or hyline cartilage. There are 3 types: sutures, gomphosis, and synchrondosis

Sutures

fibrous type found attaching the bones of the skull

Gomphosis

composed of cone shaped bone held into socket (depression) by fibrous tissue (teeth)

Synchrondosis

held together by hyline cartilage (epiphyseal plate of the long bones)

Amphiarthosis (slightly movable)

these joints lack synovial cavity, and are held together by fibrous or fibrocartilage. There are 2 types: syndesmosis and symphysis

Syndemosis

fibrous articulation at the distal ends of the tibia and fibula forming the ankle with the talus

Symphysis

fibrocartilage disk which attach the bone to each other found in the vertebral column and the pelvis

Diarthrosis (freely movable - synovial)

contain both a synovial cavity and membrane, articular cartilage (hyaline cartilage) at the articular ends along with the ligaments forming an articular capsule. There are 6 principle types: gliding, hinge, pivot, ellipsoidal (condyloid), saddle (sellaris), ball and socket

Gliding

articulating surfaces are flat with the movement being back and forth on a single axis (uniaxial) found in the carpel and tarsal bones moving against each other. The movement is limited by the ligaments

Hinge

convex surface on one bone fitting into a concave surface of the other allowing movement along a single axis (uniaxial) with the flexion of extension of the articulation found at the elbow between the ulna and humerus and knee between the femur and tibia

Pivot

rounded or pointed surface on one bone fitting into a ring formed by ligament and bone on the other allowing rotation movement around on axis - C1 and C2; radius and ulna

Ellipsoidal (condyloid)

oval shaped condyle on one bone fitting into an elliptical cavity of another bone allowing movement in 2 planes (biaxial) - flexion and extension as well as abduction and adduction plus circumduction found in the carpels with the radius and mandible with the temporal in the skull

Saddle (sellaris)

surface of one bone is saddle shaped and articulates with another bone like a rider (note may be 3 bones working to form an articulation) allowing movement (biaxial) of flexion and extension; abduction and adduction and circumduction found between the trapezium (carpal) and metacarpal I in the thumb; ankle between the tibia, fibula, and talus (tarsal) to form the ankle

Ball and Socket

ball shaped surface on one ball fitting into a cup like depression on the other bone allowing movement through all 3 planes (triaxial) - flexion and extension; abduction and adduction and rotation - shoulder between the clavicle, scapula, and humerus; and hip between the femur and pelvis

Movements found in diarthrosis articulations

elevation & depression, protraction & retraction, dorsi-flexion & plantar flexion, supination & pronation, inversion & eversion

Elevation & Depression

shoulder & whole body - raising or lowering the shoulder - confident or weak

Protraction & Retraction

mandible and shoulder - thrusting forward or pulling back - aggressive or submissive posture

Dorsi-flexion & Plantar Flexion

foot - pointing of toes upward or downward

Supination & Pronation

hand & whole body - either in the anatomical postion or reversing the anatomical position - laying on your back or facedown

Inversion & Eversion

ankle (foot) - sole of foot turn lateral or medial