Tissue

Functions
1. Supportbody’s framework
2. Protection- encloses organ systems
3. Movement-joints of bones act as levers that move as muscles contract.
4. Mineral storage- calcium, phosphorus, etc.
5. Hematopoiesis- blood cell formation

Skeletal System
• Includes two types of connective tissue:
– Bone
– Cartilage
• Other tissues also discussed:
– Blood
– Nervous tissue
– Loose fibrous tissue
– Adipose
– ETC.

Bone Tissue
• Refer back to Connective Tissue Notes: Bone
• Hard calcified matrix filled with collagen fibers
• Hard tissue gives it a support and protective function

Bone Matrix
• The intracellular substance of bone is made of two components:
– In organic salts
– Organic Matrix

Inorganic salts
• Calcified and hard nature of bone results from salt minerals.
• Calcium & phosphate
• Osteoporosis is characterized by a loss of these bone minerals

Organic Matrix
• Collagenous fibers
• Protein & polysaccharides (ground substance)
– Provide support & adhesion between cellular & fibrous elements
• All organic substance give bone a plastic like resilience so that applied stress (with in reason) does not result in frequent crush or fractures.

Refer back to Connective Tissue Notes: Bone
• Compact bone
– Contain cylinder Osteons
– Osteons contain: Lamellae, lacunae, canaliculi,
Haversian canal.
– Haversian canals are connected by transverse
Volkmann’s canals.
• Volkmann’s canals contain nerves & blood vessels that carry blood & lymph to osteons.

Microscopic structure of bone
• Cancellous (spongy) bone
– Found sandwiched between compact bone.
– No osteons
– Contains needle like
Trabeculae
– Bone cells found in trabeculae
– Nutrients and waste passed through canaliculi by diffusion
– Bone marrow found within spongy bone

Refer back to Connective Tissue Notes: Bone
• Osteoblasts: bone forming cells
• Osteocytes: mature osteoblasts trapped within lacunae.
• Osteoclasts: Bone destroying cells

Bone Marrow
• Soft diffuse connective tissue: myeloid tissue
• Site of blood cell production
• Found in cavities of long bones & spongy bone.

• Red marrow
– Found in all bones of an infant or child’s body
– Produces red blood cells
• Yellow marrow
– Red is replaced by yellow marrow as a person ages
– Marrow is saturated with fat and no longer active in blood production
• In adults, ribs, vertebrae, humerus, pelvis, & femur have red marrow

Bone marrow transplant

Types of Bone
• Long bones
• Short bones
• Flat Bones
• Irregular Bones

Long Bones
• Long
• Shaped ends
• Femur & Humorous are examples of long bone

Long bones

• Cube or box shaped
• Broad
• Wrist
(carpals) & ankle
(tarsals) bones
Short Bones

Short bones

Flat Bones
• Broad and thin with a flat
& often curved surface.
• Some skull bones, shoulder blades, pelvis, ribs, and sternum are flat.

Irregular Bone
• Often in clustered groups.
• Various shapes & sizes
• Vertebrate, sacrum, facial bones are irregular.

Parts of a long bone
• Diaphysis
• Epiphyses
• Articular Cartilage
• Periosteum
• Medullary (marrow) cavity
• Endosteum

Diaphysis
• Main Shaft like portion.
• Hollow cylinder shape
• Thick compact bone
• Provides strong support for weight

Epiphyses
• Ends of bone
• Bulb shape
• Space near joint for muscle attachments
• Spongy (cancellous) bone
• Red marrow fill spaces in spongy bone

Articular Cartilage
• Thin layer of hyaline cartilage
• Covers joints of Epiphyses
• Cushions joints or blows

Periosteum
• Dense white fibrous membrane that covers bone
(not joints)
• Fibers of periosteum penetrate bone, sticking them together.
• Muscle tendon fibers interlace with periosteum fibers as well.
• Contains bone forming and destroying cells (Osteoblasts
& Osteoclasts)

Medullary Cavity
• Tube like hollow space in the diaphysis
• Filled with connective tissue rich in fat: yellow marrow

Endosteum
• Thin epithelial membrane that line medullary cavity

• Using materials provided and page 191, create a model of a long bone.
• Parts
– Periosteum  plastic wrap
– Spongy bone  sponge
– Compact bone (diaphysis)  clay
– Yellow marrow  petroleum jelly
• Label each part

• Skeletal system-Storehouse of 98% of body’s calcium
– Maintains constancy of blood calcium levels
• Calcium acquired during bone formation/remodeling
– Homeostasis of calcium ion concentration essential for:
• Bone formation, repair
• Blood clotting
• Transmission of nerve impulses
• Maintenance of skeletal & cardiac muscle contractions

• Parathyroid hormone
– Regulates calcium
– Stimulates osteoclasts to breakdown bone matrix
& release calcium in blood
– Increases renal absorption of calcium into urine
– Stimulates vitamin D synthesis
• Calcitonin
– Stimulates osteoblasts, inhibits osteoclasts.
– Reduces levels of circulating calcium, keeping it in the bones.

Development of Bone
• Osteogenesis –development of bone from cartilage.
• Process can happen in two ways:
– Intramembranous Osteogenesis which is the direct laying down of bone without the presence of cartilage.
– Endochondral Osteogenesis which involves bone formation from cartilage.

Epiphyseal plate
• Cartilage between diaphysis & epiphysis that functions in bone growth.
• Absent in adults that have stopped growing.
• Fractures of epiphyseal plate often found in adolescence.

Bone Growth and Resorption
• Bones grow by the combined action of osteoclasts and osteoblasts
• Osteoclasts enlarge diameter of medullary cavity
• Osteoblasts build new bone around outside of bone.

• Fracture-break in the continuity of the bone
1. Vascular damage initiates repair.
2. Fracture hematoma-blood clot that occurs after fracture.
3. Hematoma is resorped and a Callus, specialized repair tissue, binds fracture.
4. Callus is then replaced with normal bone tissue.
Hematoma
Callus
New bone tissue

Fracture trends
• Higher in seniors because bone density decreases.
• Men have a lower rate of fracture because men generally have denser bones then women.
• Fractures usually happen in thin, flat bones, and especially at the ends of bones.

Cartilage
Refer to notes: Connective tissue- Cartilage
• Types of cartilage: Hyaline, Fibrocartilage,
Elastic
• Growth:
– Interstitial Growth: Cartilage cells divide and secrete more matrix
• Seen in childhood
– Appositional Growth: Chondrocytes in perichondrium divide and secret matrix
• Seen in adulthood

• Find out the rate of fractures in each age group.
• Answer the questions.
• Then as a group (3-
4), create a large graph showing the trend of fractures in the demographics studied.
• Use
for women’s line and Δ for men’s line.