Anatomy and Physiology I
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Anatomy and Physiology I Unit 7: The Skeletal System. Physiology of the Skeletal System. Skeletal System. Bones are made of several tissues Primarily made of collagen and hydroxyapatite - Ca 10 (PO 4 ) 6 (OH) 2 About 206 bones in the human body. Functions of Skeletal System.

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Anatomy and Physiology I

Unit 7: The Skeletal System

Physiology of the Skeletal System

Skeletal system
Skeletal System

  • Bones are made of several tissues

  • Primarily made of collagen and hydroxyapatite - Ca10(PO4)6(OH)2

  • About 206 bones in the human body

Functions of skeletal system
Functions of Skeletal System

  • SUPPORT: Hard framework that supports and anchors the soft organs of the body.

  • PROTECTION: Surrounds organs such as the brain and spinal cord.

  • MOVEMENT: Allows for muscle attachment therefore the bones are used as levers.

  • STORAGE: Minerals and lipids are stored within bone material.

  • BLOOD CELL FORMATION: The bone marrow is responsible for blood cell production.

Parts of the skeletal system
Parts of the Skeletal System

  • Axial skeleton

    • Skull and bones that support it

    • Includes vertebra and ribs

    • 80 bones

  • Appendicular skeleton

    • Limbs

    • 126 bones

Features of a Long Bone:

Epiphysis: Ends of the bone.

Diaphysis: The shaft of the bone which surrounds the medullary cavity.

Articular Cartilage: Cushions the ends of the bones and allows for smooth movement.

Epiphyseal Plate:

Areas made of cartilage allowing for the growth of the bone.


  • Where bone meets bone

  • Ligament – holds bone to bone

  • Types of joints:

    • Immovable - skull

    • Ball-and-socket - shoulder

    • Hinge - knee

    • Pivot – forearm

    • Gliding - vertebrae


  • Cartilage covers ends of movable bones

    • Reduces friction

  • Lubricated by fluid from capillaries

Bone structure
Bone Structure

  • Periosteum – hard outer covering

    • Cells for growth and repair

  • Compact bone – hard strong layer

    • Bone cells, blood vessels, protein with Ca and P

  • Spongy bone – at ends of long bones

    • Has small open spaces to lighten weight

  • Marrow cavity – hollow in middle of long bones

Bone marrow
Bone Marrow

  • Red marrow – produces blood cells and clotting factors

    • Found in humerus, femur, sternum, ribs, vertebrae, pelvis

    • Produces RBC 2 million per second

  • Yellow marrow – stores fat

    • Found in many bones

Haversian system
Haversian System

  • Structure of compact bone

  • Rings of bone tissue with blood vessels and nerves in the center

Bone development
Bone Development

  • Initial skeleton of cartilage in infants

  • Replaced with bone by osteoblasts

  • More than 300 bones at birth – fuse to 206

  • Always growing and breaking down

    • Osteoblasts – form new bone cells

    • Osteoclasts – break bone cells down

    • Osteocytes – mature bone cells

Broken bones
Broken Bones

  • Fracture is a break of the bone

  • Simple or Complex fracture

  • Regrowth of bone:

    • Spongy bone forms in first few days

    • Blood vessels regrow and spongy bone hardens

    • Full healing takes 1-2 months

Homeostatic Imbalances


  • Disease of children due to a lack of vitamin D.

  • Calcium is not deposited in bones.

  • Bones become soft.

  • Bowing of the bones, and other deformities occur.

Homeostatic Imbalances


  • “Rickets” of adults.

  • Due to a lack of vitamin D.

  • Calcium is not deposited in the bones.

  • Bones become brittle.

Homeostatic Imbalances


  • Bone reabsorption is greater than bone deposition.

  • Due to any of the following:

  • Lack of estrogen in women.

  • Lack of exercise to stress the bones.

  • Inadequate intake of calcium and phosphorus.

  • Abnormalities of vitamin D metabolism.

  • Loss of muscle mass.

Age related dysfunctions
Age Related Dysfunctions


Osteoarthritis- 90% of pop. By age 40

chronic inflammation of articular cartilage

can be normal age-dependent change

can also be pathology due to ?

Age-related changes

decrease blood supply



Decline in Bone Density

Bone Resorption > Bone Deposition

Increase Risk for Fracture

compression fractures of vertebrae

hip fractures

Role of calcium, vitamin D, estrogen, exercise

Calcitonin vs. Parathyroid Hormone