Download Chapter 7 Part 1 Notes

Chapter 7 ­ The Skeletal System
The skeletal system is a framework of bones and cartilage that protects organs and allows movement. It is composed primarily of connective tissue.
Adult skeleton is composed of 206 named bones
I Function of the skeletal system
A Supporting framework ­ gives form and shape to the body
B Protection of delicate organs. ie. brain, lungs, heart
C Movement: Provides a place for muscle attachment
D Storage of minerals, especially Ca and P
E Supplies blood cells ­ red bone marrow is the site of hemopoiesis.
F Storage of energy ­ yellow bone marrow is primarily adipose tissue.
II Principle types of bones based on shape.
A long bone
B short bone
C flat bone
D irreglar bone
E bones classified by location
1 sesamoid
2 sutural
Title: Feb 5­9:42 AM (1 of 10)
III Histology of bone tissue (microanatomy)
A Osseous tissue consists of a great deal of intercellular material (inorganic salts and collagen fibers) surrounding widely scattered separate cells.
B Four (4) types of bone cells
1 osteoprogenitors (stem cells): undergo mitosis forming osteoblasts. 2 osteoblasts: bone forming cells secrete the proteins that eventually harden (calcify) forming new bone matrix. Do not have the ability to undergo mitosis.
3 Osteocytes: isolated in their lacunae, these are mature bone cells. 4 Osteoclasts: delvelop from a type of white blood cell called monocytes. They reabsorb or break down the hard bone matrix, important to repair, remodeling, and growth.
C Types of Bone Tissue
1 Compact bone tissue
A Dense containing little space
B forms the external portion of all bones
C provides protection and support
D Basic unit of compact bone is the osteon (Haversian System)
2 Spongy bone ­ cancellous A Ususally doesn't have osteons instead a lattice­work of thin bone called trabeculae
B Spaces of trabeculae are filled with red bone marrow
C highly vascular tissue
D Commonly found in: short, flat, irregular bones, and the ends (epiphysis) of long bones.
E Spongy bone is the only site of hemopoiesis in adults.
Title: Feb 7­9:12 AM (2 of 10)
Title: Feb 12­9:40 AM (3 of 10)
IV Macro­anatomy of a typical long bone
A Epiphysis: Ends of the bone ­ proximal epiphysis is closer to the body connection, distal epiphysis is further away from the connection with the trunk.
1 Covered with articular cartilage that protects the epiphysis during movement.
2 Composed primarily of spongy bone.
3 Red bone marrow is found in the spaces of the spongy bone
B Diaphysis: The long shaft of the bone
1 Composed primarily of compact bone
2 The center is hollowed out forming the medullary cavity
3 Yellow bone marrow fills the medullary cavity in adult bones
4 The diaphysis is covered with a fibrous membrane sheath called the periosteum. The periosteum contains nutritive blood vessels, bone forming cells, and is continuous with tendons/ligaments.
5 The medullary cavity is lined by the endosteum which is similar in function to the periosteum.
C Epiphyseal plate/line separated the diaphysis from epiphysis.
1 In growing children, this is a plate of cartilage AKA the growth plate
2 In adults the cartilage has ossified resulting in a line. this indicates that no more linear growth will occur
D Nutrient Vessels: Arteries, veins, and nerves all nourish the bone
Title: Feb 7­9:39 AM (4 of 10)
Diagram of a typical long bone
Title: Feb 17­3:37 PM (5 of 10)
V Development and maintenance of Bone
A Formation of the potential skeleton first begins at about 6 weeks after conception in the form of fibrous cartilage or hyaline cartilage.
B At about 8 weeks of development, the cartilage starts to be replaced with bone. This is called ossification.
C The major ossification associated with growth occurs during the first 25 years. After that the process is limited to repair and maintenance.
D There are two types of ossification processes. It is determined by the type of cartilage it occurs in. Title: Feb 17­3:42 PM (6 of 10)
1 Intramenbranous Ossification
a Original model is fibrous membrane. Osteoprogenetors produce osteoblasts which secrete a collagenous matrix.
b Calcium salts are deposited (calcification) to form the trabeculae of spongy bone
c Spaces in the bone are filled with red bone marrow.
d The surface layers reform as compact bone.
e Cranial bones and clavicles (collarbones) are formed this way. the "soft spots" AKA fontenels of an infant skull are places where the boney plates haven't completely ossified.
Title: Feb 17­3:57 PM (7 of 10)
2 Endochondral Ossification
a Original model is cartilage
b Long bones and most other bones are formed this way
c Primary site is the diaphysis, secondary site are the epiphyses, and the final site are the eiphyseal plates.
d The medullary cavity is carved out by osteoclasts
e Rate of growth is controlled by hGH ( human growth hormone) and is usually completed by age 25.
E Growth and Maintenance of bone
1 Balance between osteoblasts and osteoclasts
2 Sufficient quantities of calcium and phosphorus in the diet
3 Vitamins D, C, A, and B12
4 Hormones: hGH, Sex hormones estrogen and testosterone, insulin, and thyroid hormones.
5 Weight bearing exercise: this creates tiny currents of electricity called piezoelectric effect which stimulates bone formation
Title: Feb 17­4:05 PM (8 of 10)
F Homeostasis of calcium levels in the blood.
1 Controlled by a negative feed back mechanism controlled by the parathyroid gland and thyroid gland.
a calcitonin is released in response to high blood calcium level. Osteoblasts are stimulated and calcium is deposited in bone. (increase bone growth)
b PTH (parathyroid hormone) is released in response to low blood calcium levels. Osteoclasts are stimulated and calcium is released from bone back into the blood. (bone breakdown)
Title: Feb 17­4:16 PM (9 of 10)
VI Surface Features of Bones
A Depressions, holes, & extensions that serve a certain function
1 Form joints
2 Site for muscle attachment
3 Passage way for nerves and blood vessels
B Types of holes and depressions
1 Foramen: hole in a bone ex. foramen magnum
2 Fossa: depression usually to form a joint. ex. olecronon fossa
3 Meatus: tubelike opening. ex. auditory meatus
C Types of extensions:
1 Head: rounded end. ex. head of the femur
2 Condyle: Knuckle­like. ex. occipital condyle
3 Facet: Flat surface. ex. rib facets 4 Spine: Sharp, pointy extension. ex. spines of the vertebrae
5 Trochanter: large bump: ex. greater trochanter of the femur
6 Crest: ridge­like edge. Ex. illiac crest.
Title: Feb 17­4:25 PM (10 of 10)