Skeletal System: Tissue and physiology

Skeletal tissue is the most distinctive form of connective tissue.

Chapter 7 Notes

Functions of Skeletal Tissue

Support•Ex. Arch of foot, vertebral column,

etc. Protection

•Ex. Skull protects the brain, rib cage protects lungs and heart.

Movement•Occurs with the help of joints - act

as levers•Muscle contraction pulls on bones

= movement

Functions of Skeletal Tissue Mineral reservoir

o Calciumo Homeostasis of blood calcium levels

Hemopoiesis - blood cell formationoOccurs in red bone marrow

»chest»spinal column in adults»base of skull»upper arm and thigh»In infants or child, all bone marrow

is red.

ADULTS

Bone ShapesBone Shapes

• Long boneLong bone - consists of 6 parts.

Ex. femur, humerus• Short boneShort bone - ex.

Carpals = fingers and toes

• Flat BoneFlat Bone – scapula = back (shoulder blade)

• Irregular boneIrregular bone - vertebrae

Structure of Long Bone

• Diaphysis– Main shaft– Strong support– Hollow = decrease

in weight

Structure of Long Bone

• Epiphysis– Ends of long bone– Bulbous shape

allows for muscle attachment and gives stability to joints

– Contains spongy tissue

• contains marrow - red or yellow

Spongy bone

Compact bone

Structure of Long Bone

• Articular cartilage– Covers joint surface

of epiphysis– Cushions jars and

blows

Structure of Long Bone

• Periosteum– Dense fiberous

membrane– Covers bone except at

joints– Tedons interlace with

and anchor muscles– Contain many blood

vessels (connects with haversian canal)

– Osteoblasts (bone forming cells) compose inner layer

Structure of Long Bone

• Medullary Canal– Tube of

diaphysis– Contains marrow

• Endosteum– Membrane – Lines medullary

cavity of long bone

Long Bone Anatomy

http://kidshealth.org/misc/movie/bodybasics/bone.html

Haversian System

•Identifies microscopic structure of compact bone in the diaphysis

Haversian System Structure

• Lamellae (Lah-Mel-e)– cylinder shaped

layers of calcified matrix (non-living)

• Lacunae (la-Kew-nah)– small spaces– contains tissue fluid

where bone cells (osteocytes) live

– imprisoned between lamellae

Haversian System Structure

• Canaliculi (Ka-NALi-ku-li)

– ultra small canals– radiates out from lacunae

to connect each other– connects also to

haversian canal

• Haversian canal– Contains blood vessels

and lymphatic tissue– Gives nutrients to lacunae

through canaliculi– Gives nutrients to

osteocytes

Haversian System

Bone Development and Growth

• Osteogenesis - the process of bone formation– At 12 weeks the

skeleton has formed-made of cartilage and fibrous tissue.

Bone Development and Growth

• Fontanels - "soft spots" of an infant's skull

Osteogensis

• Intramembranous Development– Prebone structure of skull and mandible– Takes place within connective tissue– Connective tissue enlarges to form osteoblasts

- bone forming cells.– Bone matrix is formed– Matrix is calcified by deposits of calcium and

salts.– Flat bones grow by adding to their outside

borders.

Osteogensis Continued

• Endochondral (all other bones)– Begin as cartilage– Cartilage develops periosteum - enlarges into a

ring– Cartilage calcifies– Ossification, hardening of bone, progresses

toward each epiphysis. (involves addition of Ca+ and Phosphorous ions)

– During bone growth, ephiphyseal cartilage remains between ends and shaft = growth plate.

Osteogensis Continued

Major stages (a-d fetal, e child, f adult) in the development of the endochondral bone.

Bone Growth

• Diameter– Osteoclasts - enlarge diameter of

medullary cavity by eating away wall.– Osteoblasts - build new bone at

periosteum– Occurs throughout life

http://www.personal.psu.edu/staff/m/b/mbt102/bisci4online/bone/bone5.htm

Bone Growth Continued

• Childhood– Bone ossification is greater than bone

resorption (decomposition) = taller• Adulthood

– Bone ossification and resorption equal one another.

– At 35-40, bone ossification decreases and resorption is greater.

• Become hollow• Vertebrae collapse = height decrease• Brittle bones = death

Bone Growth

http://www.pennmedicine.org/encyclopedia/em_DisplayAnimation.aspx?gcid=000112&ptid=17

Bone marrow aspiration, direct removal of a small amount (about 1–5 millilitres) of bone marrow by suction through a hollow needle.

Bone Fracture

• Bone Fracture - break in continuity of bone.– Types

•Simple - skin remains unbroken•Compound - broken ends protrude through

skin– Easily infected - osteomyelitis

http://www.muschealth.com/video/Default.aspx?videoId=10226&cId=2&type=rel

Bone Fractures Continued

• A complete fracture is when the bone has broken into two pieces.

• A greenstick fracture is when the bone cracks on one side only, not all the way through.

• A single fracture is when the bone is broken in one place.

• A comminuted (say: kah-muh-noot-ed) fracture is when the bone is broken into more than two pieces or crushed.

• A bowing fracture, which only happens in kids, is when the bone bends but doesn't break

• An open fracture is when the bone is sticking through the skin.

Bone Fractures Continued

Bone Fractures Continued

• Repair - fracture healing– Damage to blood vessels begins repair

sequence.– Dead bone is removed by osteoclasts-

resorption.– Osteoclasts used as framework for repair

tissue called callus.– Callus tissue bonds broken ends of bone

outside.– Callus tissue binds medullary cavity.– Callus tissue is molded and replaced with

bone.• Electrically induced osteogenesis - uses

electrical stimuli to heal fractures.

Bone Fractures Continued

• Major steps in the repair

of a fracture.

Osteoporosis

• Loss of calcified matrix & callogenous fibers.• Occurs most frequently in elderly, white

females.• Decrease levels of estrogen and testosterone.

– Decreased osteoblast activity– Decreased maintenance of existing bone

• Bone Degeneration– Spontaneous fractures– Curvature of the spine

• Treatment– Estrogen therapy - after menopause– Dietary supplement of calcium and vitamin D.http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter6/animation__osteoporosis.html

http://www.muschealth.com/video/Default.aspx?cId=2

Cartilage

• Cartilage - connective tissue– Types

• Hyaline • Elastic Cartilage• Fibrocartilage

Hyaline

• Most abundant• Semi-transparent-

bluish, opalescent• Covers articular

surface of bone• Forms ends of ribs

that join to sternum• Forms rings in

trachea, bronchi of lungs, & nose

Elastic Cartilage

• Elasticity and firmness

• Fibers form to external ear, epiglottis, tubes in ear, nasal cavity

• Yellowish in color

Fibrocartilage

• Greatest tensile strength

• Intervertebral disks, point of attachment of some large tendons to bones.

Structure of Cartilage

• Chondrocytes - cartilage cells.• Avascular - contain no blood vessels.

– Receive oxygen and nutrients through diffusion.

• Increase of collagenous fibers and matrix embedded in a gel (not calcified).

Function of Cartilage

• Shock absorption• Resists collapse of passageways• Allows bone growth