Skeletal System

Chp. 5

Recall that connective tissue consists of a matrix with cells suspended w/in it--the type of matrix & cells determine type of tissue.

1. Bones - hard elements of skeleton.

2. Ligaments - dense, fibrous connective tissue that serves to bind bone-to-bone.

3. Cartilage - collagen & elastin fibers suspended in gel-like matrix [ground substance].

Skeletal System

Composed of 3 Types of Connective Tissue

5 Functions of Bones

1. Support

2. Movement

3. Protection

4. Formation of blood cells

5. Mineral storage

1. Bone: hard inorganic matrix of calcium salts

a. Compact Bone:

• Dense - extracellular deposits of calcium phosphate matrix w/ living cells

• Osteocytes- living mature bone cells that maintain structure of bone

• forms shafts & covers ends of long bones

• filled with yellow marrow

• Yellow marrow = Primarily fat for energy reserves

• Contains blood vessels & nerves

Skeletal System cont.

b. Spongy Bone:

• porous bone found inside enlarged knobby ends of bones [knob = epiphysis]

• Internal latticework makes bones lighter & stronger

• Trabeculae = latticework of bones made of calcium minerals + living cells

• red marrow - found in spaces of trabeculae w/in long bones of upper arms & legs

Stem cells w/in red marrow produce RBC’s

Skeletal System cont.

Osteons [Haversian Systems] Cylindrical Structures (see text Fig 5.1)

Osteons - as compact bone develops & hardens (ossifies) the osteocytes are trapped in hollow chambers within cylindrical osteons in such a way as to maintain contact with other osteocytes yet provide them a strong matrix to support them.

Blood vessels traveling through the central Haversian canal feed the osteocytes via cell-to-cell diffusion. Waste products Diffuse away from cells, back to blood vessels.

Periosteum

Tough Connective Tissue covering bones

• Contains bone forming Osteoblast cells

Structure of Bone

Human Biology

Figure 5.1

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*Make note of these

Cartilage - fibers of cartilage & elastin in gel-like matrix

Function: support

Types:

• Fibrocartilage - between vertebral disks, in knee joint

• Hyaline - embryonic “model” for bones, covers ends of mature bones found in joints.

• Elastic cartilage - outer ear, part of epiglottis

Ligaments- attach bone to bone

Cartilage and Ligaments

Prenatal: cartilage model

Fetus: some conversion to bone

Childhood: primary & secondary ossification sites formed

Adolescence: cartilage growth plate elongates

Bone Development [see Fig. 5.2 from text]

Bone Development (cont.)

Figure 5.2

Changes in: (1) shape, (2) size, (3) strength

• Dependent on diet, exercise, age

Bone cells regulated by hormones

• Parathyroid hormone (PTH): removes calcium from bone

• Calcitonin: adds calcium to bone

Repair: hematoma and callus formation

Mature Bone Remodeling and Repair

Skeletal System: Frontal View

Figure 5.5

Blue = Axial Skeleton[skull, vertebral column, ribs,Sternum]

Black = Appendicular Skleton[pectoral girdle, pelvic girdle, limbs]

Axial Skeleton: The Skull [Just make note of

the number of bones in the skull]

Figure 5.6

Axial Skeleton: Vertebral Column

Figure 5.7

5 areas of Axial skeleton:cervical, thoracic, lumbar, scarum,

coccyx

Vertebral column• Regions: cervical, thoracic, lumbar, sacral,

coccygeal• Intervertebral disks: cushion vertebrae; assist

in movement, flexibility

Ribs• Twelve pairs• Bottom two pair floating

Sternum: Breastbone• Three bones fused

Axial Skeleton: Vertebral Column (cont.)

Pectoral girdle: shoulder

• Clavicle, scapulas

Pelvic girdles: hip

• Coxal bones, sacrum, pubis, ilium, ischium

Limbs

• Arms: humerus, radius, ulna, wrist and hand bones

• Legs: femur, tibia, fibula, ankle and foot bones

Appendicular Skeleton

Classified by degree of movement

• Fibrous joint: immovable (e.g., fontanels)

• Cartilagenous joint: slightly movable, cartilage connection (e.g., backbone)

• Synovial joint: freely movable (e.g., knee)

Joints (Articulations)

Synovial Joints

Figure 5.12A

Joint capsule: synovial membrane + hyaline cartilage

Synovial membrane secretes synovial fluid as

lubricant

Hyaline cartilage cushions

Synovial Joints (cont.)

Sprains: stretched or torn ligaments

Bursitis and tendinitis: inflammation of bursae or tendons

Arthritis: inflammation of joints

Diseases and Disorders of the Skeletal System