The Skeletal System

Anatomy & Physiology

OMHS

Learning Targets: I can…

• identify the skeletal subdivisions, major bones, and joints of the human body.

• describe the functions of the skeletal system.

• compare and contrast different types of bone tissue and bone cells.

• explain homeostasis of the skeletal system.

• describe different skeletal disorders.

1. Support – provides framework, supports soft tissues and provides points of attachment for skeletal muscles

2. Protection – internal organs are protected by skeleton, ex. Heart and lungs are protected by ribs

Functions - continued3. Movement – when muscles

contract, they pull on bones and produce movement

4. Mineral Storage – homeostasis mechanism that deposits and removes calcium and phosphorus on demand

Functions - continued

5. Blood Cell production – red bone marrow produces blood cells; a process called hematopoiesis

6. Storage of energy – yellow bone marrow stores lipids, an important source of chemical energy

• Bones are grouped according to their shape

1. Long – legs, toes, arms, fingers2. Short- wrist, ankle3. Flat – cranial, sternum, ribs,

scapulas4. Irregular – vertebrae

• The matrix consists of mineral salts (calcium phosphate and calcium carbonate)

• Bone may be classified as compact or spongy

• Compact Bone – dense layer of bone containing Haversian canal, lamellae (rings of matrix); between lamellae are lacunae that house the osteocytes.

• Spongy bone – has irregular spaces that help reduce the weight of the bone; the site of hemopoiesis

Hemopoiesis (or Hematopoiesis)

The process through which blood cells are formed and differentiated into …

• red cells (erythrocytes) – most abundant

• white cells (leukocytes) – defense system

• platelets (thrombocytes) – clotting agents

• Diaphysis – shaft of bone; contains compact bone surrounding yellow marrow (fat storage)

• Epiphysis –ends of bone; made of spongy bone (site of hematopoiesis)

• Periosteum- tough connective tissue that covers the bone; continuous with tendons and ligaments

1. Osteoprogenitor cells (bone stem cells) give rise to osteoblasts. (baby bone cell)

2. Osteoblasts - cells that form bone; when they become isolated in the matrix, they become mature bone cells (teenager)

Osteocytes – mature bone cells (grandfather)

3. Osteoclasts - function in reabsorption of bone (they destroy bone) (cut down bone)

• Osteoblasts lay down the osteiod matrix (protein) in lamellae or layers.

• The calcified or hard salts of the matrix are laid down later. The salts come from the blood supply (Haversian canal) and move through the lamallae using the canaliculi (small tubes throughout matrix).

• Bone growth & hardening is stimulated by stress. Therefore, exercise is important to maintain bone health.

• Osteoclasts and osteoblasts are constantly reforming and restructuring bone; but the total mass of bone remains fairly constant

• When the body needs calcium, osteoclasts destroy bone to release calcium into the bloodstream

• Therefore, you must include calcium in your diet so that osteoblasts can re-form bone

• Minerals – calcium and phosphorus must be included in the diet

• Vitamins – vit. D is required for the absorption of calcium; vit. C is required to maintain the matrix; vit. A regulates bone remodeling activity; vit. B12 may also help

Hormones needed for bone tissue activity:1. Human growth hormone is responsible

for the growth of bones 2. Estrogen & testosterone aid in new

bone growth3. Calcitonin promotes bone formation

and decreases blood calcium level4. Parathyroid hormone increases blood

calcium level (promotes destr. of bone)

• Osteoporosis is caused when a person’s bone density drops significantly.

• Osteoporosis happens when osteoclast activity is greater than osteoblast activity.

• It is especially prevalent is post-menopausal women because of the drop in estrogen.

• Treatments – increase in hormones such as calcitonin, testosterone, & estrogen.

• Exercise is also beneficial because increases stress on the bone which aids in bone development.

3 types of joints: A.Fibrous- skullB. Cartilaginous-

vertebraeC. Synovial-

articulating bones

6 Different Types of Synovial Joints:

1. Ball and socket (hip)

2. Ellipsoidal (metacarpals)

3. Gliding (wrist)

4. Hinge (elbow)

5. Pivot (ulna & radius)

6. Saddle (wrist & thumb)

• 1: Ball and socket joint; • 2: Ellipsoid joint (Condyloid); 3: Saddle joint; • 4 Hinge joint; 5: Pivot joint;

• When bone marrow is transplanted it is taken from the donor during surgery using a long needle inserted into the superior end of the femur (2% of bone marrow is taken).

• The bone marrow is then given intravenously (IV- through the vein) into the circulatory system.

• The bone marrow then travels to the bones, since it is a stem cell it replicates quickly and takes root in all of the bones.