chapter 5 skeletal system

Chapter 5

The Skeletal System

I. Divisions of the Skeletal System

The axial skeleton – bones of the center of the body; spine, cranium,

The appendicular – bones of the limbs and girdles

Joints, cartilages, and ligaments

II. Functions of Bones Support against gravity – supports the body

and anchors the organs; act as pillars to hold up the body.

Protection – cranium protects the brain; ribs protect heart and lungs; vertebral column protects the spinal chord

Movement – Muscles use bones as levers for movement

Storage – fat is stored in bones as well as minerals such as calcium and phosphorus.

Hematopoiesis – forming blood cells

III. Classification of Bones

206 bones in the body Two types of bone:

Compact bones is dense and looks smooth and hard; usually the shaft of a long bone.

Spongy bone is small needle like pieces of bone and lots of open space; usually the heads of a long bone.

III. Classification of Bone Classification based on Shape

Long bones – longer than they are wide; shaft with a head on both ends; femur, humerous, radius, ulna.

Short bones – cube shaped; mostly spongy; wrist and ankle bones.

Flat bones – thin and flattened; usually curved. Two layers of compact bones sandwiching a layer of spongy bone; skull, rubs, sternum

III. Classification of Bones

Irregular bones – “catch-all” group; any bones that do not fit with the other groups; vertebrae and the hip bone.

BEGIN STUDYING THE CHART ON PAGE 115 AND 121. YOU WILL NEED TO KNOW ALL THESE!!!

IV. Structure of a Long Bone

The diaphysis (shaft) makes up most of the bone’s length and is composed of compact bone.

Covering the diaphysis is the periosteum (fibrous connective tissue)

Sharpey’s fibers secure the periosteum to the diaphysis.

IV. Structure of a Long Bone At each end of the long bones is the

epiphysis. Each epiphysis consists of a thin layer

of compact bone enclosing an area filled with spongy bone.

Articular cartilage, instead of periosteum, covers its external surface.

Articular cartilage is smooth glassy hyaline cartilage; reduces friction at joints.

IV. Structure of a long bone

Thin line of bony tissue spanning the epiphysis that looks a bit different from the rest of the bone. Its called the epiphysial line.

In young bones there is an epiphyseal plate made of cartilage that allows the bone to grow.

IV. Structure of a long bone

The shaft is a storage area for adipose tissue (fat). This is called yellow marrow cavity or the medullary cavity.

In infants this area makes blood cells and red marrow is found there.

KNOW THE CHART ON PAGE 115.

V. Bone Markings

There are two categories of bone marking Projections or Processes – grow out from

the bony surface Depressions or cavities – indentations in

the bone.

V. Bone Markings

Tuberosity – large rounded projectsion; make be roughened

Crest – Marrow ridge of bone; usually prominent

Trochanter – Very large blunt, irregularly shaped process (only on the femur)

V. Bone Markings

Line – Narrow ridge of bone; less prominent than a crest

Tubercle – small rounded projection or process.

Epicondyle – raised area above a condyle

Spine – Sharp, slender, often pointed projection

V. Bone Markings

Head – Boney expansion carried on a narrow neck.

Facet – Smoth nearly flat articular surface

Condyle – Rounded articular projection Ramus – Armlike Bar of a bone

V. Bone Markings

Meatus – Canal-like passageway Sinus – Cavity within a bone, filled with

air and lined with mucous membrane Fossa (shallow, basinlike depression in

a bone, often serving as an articular surface.

Groove - Furrow

V. Bone Markings

Fissure – Narrow, slit like opening Foramin/Foramina – Round or oval

opening through a bone

VI. Microscopic Anatomy

Mature bone cells are called osteocytes. Osteocytes are found in tiny cavities

withing the matrix called lacunae. The lacunae are arranged in circles

called lamellae around a central Haversian canal.

These together make up an osteon.


Canaliculi are tiny canals that radiate outward from the central canals to all the lacunae

Bone is well vascularized and heals well.

Volkmann’s canals run at right angles to the shaft.


Calcium salts make the bone hard. The organic parts (especially the

collagen fibers) provide flexibility and great strength

VII. Bone Formation, Growth, and Remodeling In an embryonic bone - mostly hyaline

cartilage. The bones in a fetus are about 60%

bone/40% hyaline cartilage. In a child, the Epiphyseal plate is still

cartilage. In adults, Epiphyseal plate is replace

with bone leaving only the epiphyseal line.

VII. Bone Formation, Growth, and Remodeling Ossification – bone formation Osteoclasts – bone destroying cells to

release calcium into the blood Rickets – disease in children in which

the bones fail to calcify – lack of calcium in the diet or vitamin D – Legs bow under the weight of the body.

VIII. Bone Fractures

As you age, bones thin and weaken. Fractures are more common.

Fractures are treated by reduction Closed reduction – bones are coaxed back

into their normal positions by the doctor. Open reductions – surgery is performed

and the bone ends are secured together with pins or wires.

VIII. Bone Fractures

Bones must be immobilized with a cast. Healing time for simple bones is 6 to 8

months, but is longer for large bones and in elderly people.

VIII. Bone Fractures 4 events of bone fractures

A hematoma is formed. Blood vessels are ruptured and blood clots.

Fibrocartilage callus formation – slints the gap between the bones. Capillaries reform.

Bony callus formation – Fibrocartilage is replaced by bony callus

Bone remodeling – patch the bone permanently.

IX. Bone Fractures Simple fracture – Bone breaks cleanly,

but doesn’t penetrate the skin. Compound fracture – Bone protrudes

through the skin Comminuted fracture – bone breaks into

many pieces. Compression – Bone is crushed Depressed – Beon is pressed inward.

IX. Bone Fractures

Impacted Fracture – Broken bone ends are forced into each other

Spiral Fracture – Ragged break occurring when excessive twisting forces are applied to a bone.

Greenstick – Bone breaks incompletely much in the way a green twig breaks.

XIII. The Vertebral Column Formed of 26 irregular bones Protects and supports the spinal cord The sacrum is 5 fused vertebrae The coccyx is 4 fused vertebrae (tail

bone) Between individual vertebrae are

intervertebral discs made of flexible fibrocartilage which cushion the vertebrae and absorb shock.

XIII. The Vertebral Column

Young discs have more water content and are more flexible.

Body or centrum – main part of the vertebra

Vertebral arch – formed from the joining of posterior extentions; the laminae and pedicles make up the vertebral arch

XIII. The Vertebral Column Vertebral foramen – canal through which the

spinal cord passes. Transverse process – two lateral projections

from the bertebral 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 foramen, allowing a vertebra to form joins with adjacent vertebrae

XIII. The Vertebral Column The spine is divided into section:

Cervical vertebrae – first 7 vertebrae of the spine.

– First cervical vertebrae is called the atlas. The atlas has no body and articulates with the occipital condyles of the skull

– Second cervical vertebrae is called the axis. The axis acts as a pivot for rotation of the atlas (and skull). The axis has a large process called the odontoid process or dens.

– These are numbered C1, C2, C3, etc


Thoracic vertebrae include 12 individual vertebrae. They are number T1, T2, T3, etc. The body of the vertebrae is somewhat

heartshaped The two demifacets on each side receive

the ribs. The spinous process is long hooks sharply

downward.


The Lumbar Vertebrae 5 Block-like vertebrae Hatchet shaped spinous process These are the sturdiest of the vertebrae Labeled L1, L2, L3, etc.


Sacrum Fused 5 vertebrae The wing-like alae articulates with the hip Forms the posterior wall of the pelvis The midline of the sacrum is roughened by

the median sacral crest which is made from fused spinous processes.


Coccyx Remant of the tailbone that other

vertebrates have. 3 to 5 fused vertebrae

XIV. Bony Thorax or Thoracic cage

chapter 5 skeletal system

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