Skeleton System

Function of the Skeleton System

Function of the Skeleton System

• support by carrying the weight of the body

• protection of organs

• assist in movement along with the muscular system

• mineral homeostasis by controlling blood levels of calcium and phosphorus

• blood cell production (hemopoeisis)

• triglyceride storage

Long Bones

• bones that are longer than they are wide

• tibia

Short Bones

• bones that are equally long and wide

• wrist bones

Flat Bones

• bones that are thin, broad and commonly curved

• skull bones

Irregular Bones

• bones that do not fit into any other category

• vertebrae

Sesamoid Bones

• specialized bones found within tendons

• patella

Gross Anatomy of Bones

• nerves, blood vessels and cartilage

Osseous Tisse

• major structural and supportive connective tissue in the body

• the bone tissue

Marrow

• yellow is for fat storage

• red is the site of blood cell production

Compact Bone

• also called cortical bone

• solid and relatively dense external surface of all bones

Spongy Bone

• also called trabecular bone, main feature is trabeculae

• contains no osteons or central canal

• makes up most of smaller bones and epiphysis of long bones

• found where stress comes from many directions

• resembles a sponge and is the internal surface of bones

Epiphysis

• proximal portion of a bone

Metaphysis

• region of bone growth (upwards)

Diaphysis

• shaft or middle portion of a bone

Inner Layer of Periosteum

• consists of osteogenic cells

Outer Layer of Periosteum

• consists of dense, irregular connective tissue

Depressions

• where bone meets another bone

• can be facets, fovea, fossa or a groove (sulcus)

Openings

• allow blood vessels, nerves or something else to pass through

• can be a canal, fissure, foramen or fenestra

Projections

• attachment of muscles, tendons and ligaments

• can be a condyle, crest, head, tubercle, tuberosity, process, spine, trochanter or protuberance

Osteogenic Cells

• mitotically active stem cells that are found in periosteum

• differentiate into osteoblasts

Osteoblasts

• secrete the bone matrix and initiate calcification

Osteocytes

• mature bone cells that have developed from osteoblasts

• occupy lacunae and maintain the matrix

Osteoclasts

• giant, multinucleated cells related to macrophages

• breaks down the bone matrix

• regulates and forms new bone cells

• most important for disease repair

Bone Matrix

• 1/3 organic compounds of cells, collagen and ground substances

• 2/3 inorganic compound of hydroxyapatite

Nutrient Arteries

• one or more depending on the bone and supply most of the diaphysis

• can be periosteal, metaphyseal or epiphyseal

Bone Development

• called ossification

• either intramembranous or endochondral

Intramembranous Ossification

• when bone develops within a membrane

• starts off as mesenchyme cells into osteogenic cells and than osteoblasts

• osteoblasts secrete osteoid and are trapped within newly formed bone

• form trabeculae surrounded by periosteum in flat sheets

Endochondral Ossification

• bone develops from hyaline cartilage

• 6 stages

1st Stage of Endochondral Ossification

• fetal hyaline cartilage model develops and grows as chondrocytes divide

2nd Stage of Endochondral Ossification

• cartilage calcifies and bone collar forms

3rd Stage of Endochondral Ossification

• cavity forms within the cartilage model

4th Stage of Endochondral Ossification

• nutrient artery penetrates , delivering osteogenic cells and osteoclasts

5th Stage of Endochondral Ossification

• the primary ossification center forms

Last Stage of Endochondral Ossification

• bone replaces all cartilage except articular cartilage

• secondary ossification in epiphysis forms

• nutrient artery penetrates into the primary ossification centre

Epiphyseal Plate

• area of continued growth

• 5 zones

Zone of Resting Cartilage

• first area of the epiphyseal plate

• nothing occurs here

Zone of Proliferating Cartilage

• second area of the epiphyseal plate

• actively divides chondrocytes

Zone of Hypertonic Cartilage

• third area of the epiphyseal plate

• chondrocytes die

Zone of Calcified Cartilage

• fourth area of the epiphyseal plate

• where the matrix becomes calcified

Zone of Ossification

• last area of the epiphyseal plate

• osteoblasts lay down bone

Interstitial Growth

• growth at the epiphyseal plates responsible for bones increasing in length

Oppositional Growth

• osteoblasts lay down new bone under the periosteum to increase the diameter of bone

Skull

• protects the brain and sense organs

• sites of muscle attachment

• 8 cranial bones

• 14 facial bones

Parietal Bones

• has four sutures

• 2 bones

Occipital

• back of the head

• has the foramen magnum and occipital condyles

Temporal Bones

• in the tympanic and mastoid regions

• 2 bones

Frontal Bone

• forehead and upper part of the eye socket

Sphenoid Bone

• where the pituitary gland is and the optic nerve passes

Ethmoid Bone

• where the cribriform plate and nasal septum is

Soft Spots/Fontanelles

• at birth there are six spots to allow the baby to pass through the birth canal easier

• anterior fontanelle normally closes in 15 months

Nasal Bones

• 2 bones that form the bridge of the nose

Zygomatic Bones

• 2 bones that form the cheekbones

Maxilla

• 2 bones

• upper jawbone that is connected to all other bones of the face

Mandible

• lower jaw

• only moveable skull bone

Vomer

• part of the nasal septum

Palatine

• 2 bones apart of the palate

Lacrimal Bones

• 2 smallest facial bones

• medial part of the orbit that the tear ducts pass through

Nasal Conchae

• 2 bones

• nasal cavity and surface lind by olfactory epithelium

Significance of the Palate

• high metabolic rates require rapid digestion

• palate enables chewing and breathing at the same time

Hyoid Apparatus

• doesn't articulate with any other bone and is maintained by ligaments

• supports the tongue and is involved in swallowing

Vertebral Column

• starts off as 33 bones and fuses into 26 bones

• provides a flexible rod that aids in movement and protects the spinal cord

Cervical Region

• neck area (C1-C7)

Thoracic Region

• attached to pairs of ribs (T1-T12)

Lumbar Region

• largest and strongest region (L1-L5)

Sacrum Region

• attached to the pelvis (S1-S5)

Coccyx

• last region of the vertebral column (Co1-Co4)

Curvature of the Vertebral Column

• starts with the thoracic vertebrae to better distribute body weight

• cervical region develops for crawlings

• lumbar and sacral region forms to hold up the head and start to walk

Kyphosis

• hunchback

• excessive anterior curvature in thoracic region

Lordosis

• excessive posterior curvature in lumbar region

Scoliosis

• vertebral column curves laterally

Cervical Atlas

• first cervical vertebrae that is specialized

• supports the head and allows it to move up and down

• lacks a body and spinous process

Cervical Axis

• second cervical vertebrae that is specialized

• has an odontoid process

• allows for side to side movement of the head

C3-C7 Vertebrae

• have a typical vertebral structure

• foramen transversarium

Thoracic Vertebrae

• larger and stronger than cervical vertebrae

• have a longer transverse process to articulate with the ribs

Lumbar Vertebrae

• largest and strongest vertebrae

• have short and thick processes

Sacrum

• formed by the fusion of five vertebrae

• attached to the pelvic girdle and hips

Coccyx

• formed by the fusion of four vertebrae

• tip

Intervertebral Discs

• sit between adjacent vertebrae

• cushion and absorb physical shock

• facilitates movement

• resists grinding between bones

Herniated Disc

• when intervertebral discs bulge laterally

• pain is caused by a nucleus pressing against a nerve

Sternum

• flat bone that articulates with the ribs

• 3 parts

Manubrium

• top portion of the sternum

• articulates with the pectoral girdle and first ribs

Body of the Sternum

• articulates with 2-7 ribs

Xiphoid Process

• bottom portion of the sternum

• attachment for some abdominal muscles

Ribs

• 12 pairs that articulate with 12 thoracic vertebrae

• 3 types

True Ribs

• ribs 1-7 that connect directly through the intercostal cartilage

False Ribs

• ribs 8-12 that attach indirectly or not at all to the sternum

Floating Ribs

• ribs 11 and 12 that don't attach to the sternum

Pectoral Girdle

• attaches bones of upper limbs to the axial skeleton

• 2 bones that make up the shoulder

Clavicle

• articulates with the manubrium (sternal end) and scapula (acromial end)

• apart of the pectoral girdle

• provide an attachment site for muscles, acts as braces and transmits forces to the axial skeleton

Scapula

• not directly connected to the vertebral column

• apart of the pectoral girdle

• thin, triangular flat bones

Humerus

• only bone of the arm

Forearm

• radius and ulna forms the elbow, articulate with each other at both end

• olecranon prevents hyperextension

• thin at proximal end

Hand

• 8 carpals, marble-sized bones

• 5 metacarpals, palm of the hand

• 3 phalanges per finger except thumb, distal, middle and proximal

Pelvic Girdle

• differs from the pectoral girdle as it connects directly to the vertebral column

• 3 bones on each side that are fused together and come together at the acetabulum

Ilium

• superior region of the pelvis that connects to the sacrum

Pubis

• anterior region of the pelvis that joins at the pubis synphysis

Ischium

• posterior region of the pelvis

• "sit bones"

Differences between the Male and Female Pelvis

• bones are thicker and heavier in males

• female pelvic inlet is wider and the subpubic angle is wider

True Pelvis

• bony basin inferior to pelvic brim containing the pelvic organs

• part of the colon, rectum, bladder, uterus/ovaries

False Pelvis

• superior to pelvic brim bound by the ilia laterally and abdominal wall anteriorly

• intestines and muscle attachment sites