Lecture Notes: Chapter 6 - Bones and Skeletal Tissues

Cartilage Overview

• Types of Cartilage: Elastic, Hyaline, Fibrocartilage
  • Found throughout the adult body (e.g., ear, nose, joints)
• General Characteristics:
  • Surrounded by perichondrium
  • Contains chondrocytes in lacunae
  • Comprised of extracellular matrix with fibers and ground substance

Types of Cartilage

• Hyaline Cartilage:
  • Most abundant
  • Contains collagen fibers
  • Provides support and flexibility
• Elastic Cartilage:
  • Contains elastic fibers
  • Found in ear and epiglottis
• Fibrocartilage:
  • Resists compression and tension
  • Found in intervertebral discs, pubic symphysis

Cartilage Growth

• Appositional Growth: Chondroblasts in perichondrium produce new cartilage
• Interstitial Growth: Chondrocytes divide and secrete new matrix

Bone Overview

• Composed of bone tissue, nervous tissue, blood tissue, cartilage, and epithelial tissue
• Functions of Bones:
  • Support, movement, protection
  • Mineral storage
  • Blood cell formation (hematopoiesis)
  • Energy metabolism
  • Secretion of osteocalcin by osteoblasts

Bone Composition

• Organic Components:
  • Cells, fibers, ground substance
• Inorganic Components:
  • Mineral salts for hardness

Bone Cells

• Osteogenic Cells: Stem cells that differentiate into osteoblasts
• Osteoblasts: Bone matrix production (build up bone)
• Osteocytes: keep bone matrix healthy
• Osteoclasts: Bone resorption. (Break down)
• Location: found in bone tissue.

Bone Classification by Shape

• Long Bones: Longer than wide (e.g., humerus. Shaft plus end)
• Short Bones: Cube-shaped (e.g., talus)
• Flat Bones: Thin/flatten and often curved (e.g., sternum)
• Irregular Bones: Various shapes (e.g., vertebrae)

Gross Bone Anatomy

• Compact Bone: Dense outer layer
• Spongy Bone: (cancellous)
• **Internal network of bone
• with trabeculae = little ‘beams of bone
• Structure Of Long Bone **:
  • Diaphysis (shaft)
  • Epiphyses (ends)
  • Blood Vessels ( well vascularized NEEDS blood supply)
  • Medullary cavity (within the bone) - Hallow cavity that’s filled w/ yellow marrow.
  • Membranes within a Longbone :
  • Periosteum is CT covers outer surface except ends of bones.
  • Sharpeys fibers - thick bundles of collagen fibers run from periosteum into bone matrix.
• Endosteum - internal bone surface of covering made of of CT.

Structure of Short, Irregular, and Flat Bones

• Flat bone , short bones , and irregular bones contain bone marrow but no marrow cavity like long bones do. within bones structure like
• Dubloe ( internal spongy bone of flat bones)

Bone Design and Stress

• Anatomy of bone reflects stresses
• Compression/Tension: Greatest at external surfaces (15:51) time of pic

Bone Markings

• superficial surfaces of bones reflecting surfaces on them. 3 broad categories of bone markings

1. Projections for muscle attachment
2. Surfaces for joints
3. Depressions and openings for vessels and nerves (18:45) need to know !

Microscopic Bone Structure (22:31)

• Compact Bone: Contains osteons, passage way for blood vessels , lymph vessels, and nerves.

Osteons: (26:02 single osteons)

• long cylindrical structures

• function in support of

• structurally resemble rings of a tree in cross section. ALSO Contains: lamellae , central canal , perforating canals, canaliculi.

• Spongy Bone: Less complex than compact bone, NO osteons due to being too small. (27:21)

Bone Development

** Ossification ( osteogenesis) : bone tissue formation**

• membrane bones - formed directly from mesenchyme

• inteamembranous ossification: clavicle only bone formed by this.

• Endochondral Ossification: All bones included except some bones from the skull and clavicle. Bones are modeled in Hyaline cartilage. Will continue forming until early adulthood. (32:12)

Bone Growth

• Epiphyseal Plates:
• Cartilage organized quick for efficient growth.
• cartilage cells form tall stacks. Chondroblasts: @ top of stacks & divided quickly
• pushes epiphysis away form diaphysis
• lengthens entire long bone

##Hormonal Regulation of Bone Growth

• growth hormone - produced by pituitary gland , stimulates epiphyseal plates.
• thyroid hormone - ensures that the skeleton retains proper proportions.
• sex hormones (estrogen and testosterone) promote bone growth & induces closure of epiphyseal plates.

Bone Remodeling

• bone is a living tissue
• 500mg cal may enter or leave the adults skeleton each day
• bone matrix and osteocytes are removed and replaced.
• cancellous bone of skeleton is replaces q3-4 years.
• compact bone is replaces every 10 years. Bone deposition - accomplished by osteoblasts Bone reabsorption - accomplished by osteoclasts (39:00)

Bone Repair fractures

• Types of fractures: Simple, compound Simple= bone breaks clean but does not penetrates skin Compound= broken ends will protrude through skin treatment:

• closed reductions = alignment of broken bone

• Closed = bone manipulated back into position by doctor hands

• Open reduction = fixed with pins and wires.

• Healing stages: Hematoma formation, fibrocartilaginous callus, bony callus, remodeling

Bone Disorders

• Osteoporosis: Low bone mass, common in postmenopausal women
• Osteomalacia/Rickets: Vitamin D deficiency
• Osteosarcoma: Bone cancer primarily in youth

Skeleton Through Life

• Bone growth until early adulthood, balance in young adults, resorption in old age
• Importance of healthy diet and exercise for bone health