BIO 168 - Unit 3 - Bone Tissue

What are the 6 functions of the skeletal system?

1. provides support

2. protects internal organs

3. assists body movements

4. stores and releases sodium and calcium salts

5. participates in blood cell production (hemopoiesis)

6. stores triglycerides in adipose cells of yellow marrow

What are the 5 main types of bones? (based on shape)

1. long

2. short

3. flat

4. irregular

5. sesamoid

Describe lone bones.

• greater seed length than width

Describe short bones.

• cube shaped

Describe flat bones.

• thin layers of parallel plates

Describe irregular bones.

• complex shapes

Describe sesamoid bones.

• shaped like a sesame seed

What is the diaphysis?

• bone shaft of long bone

What are the epiphyses?

• both ends of long bones at the joints

What are the metaphyses?

• area between diaphysis and epiphysis

What covers both epiphyses?

• articular cartilage

What is the medullary cavity?

• hollow space within diaphysis

What is the periosteum of long bones?

• connective tissue surrounding the diaphysis

What is the endosteum?

• thin membrane lining the medullary cavity

What are osteoprogenitor cells?

• bone stem cells able to differentiate into other types of cells

What are osteoblasts?

• bone-building cells that secrete matrix

• forms bone ECM

What are osteocytes?

• mature bone cells

• maintains bone tissue

What are osteoclasts?

• cells that remodel bones and cause them to release calcium

• break-down of bone ECM

Describe compact bone.

• good at providing support and protection

Describe spongy bone.

• lightweight and provides tissue support

What are periosteal arteries?

• enter the diaphysis through Volkmann’s canals

• accompanied by periosteal veins and nerves

What are nutrient arteries?

• enters the center of the diaphysis through a nutrient foramen

• nutrient veins exit via same canal

What parts of bones have their own veins?

• metaphyses and epiphyses

Describe red bone marrow.

• loose areolar connective tissue

• predominant in infants and young children

Describe yellow bone marrow.

• for fat storage

• bone marrow transplants

What are the organic components in bone?

• bone cells and osteoids

What are the inorganic compounds in bone?

• mineral salts

What is ossification?

• osteogenesis

• process of bone formation

What are the 4 situations where bones form?

• embryological and fetal development

• when bones grow before adulthood

• when bones remodel

• when fractures heal

What are the 2 forms of ossification?

• intramembranous

• endochondrual

When does intramembranous ossification?

• occurs in flat bones when connective tissue membrane is replaced by bone

What is endochondral ossification?

• replaces cartilage with bone in developing embryo and fetus

• also occurs in epiphyseal plates of long bones as they grow in length

What cells help bones thicken?

• cooperative action of osteoblasts and osteoclasts

What are the 3 phases of bone healing?

1. reactive phase

2. reparative phase

3. bone remodeling phase

What is the reactive phase of bone healing?

• early inflammatory phase

What is the reparative phase of bone healing?

• includes formation of a fibrocartilaginous callus first and bony callus second

What is the bone remodeling phase of bone healing?

• last step as the bony callus is remodeled

What is an open (compound) fracture?

• fracture where broken bone pierces the skin or an open wound exposes the bone

What is a comminuted fracture?

• bone shatters into 3 or more pieces or fragments

What is a greenstick fracture?

• incomplete break where a bone bends and cracks on one side without completely snapping in half

What is an impacted fracture?

• occurs when a bone breaks, and the force of the injury drives the broken ends into each other

What is a pott fracture?

• a severe break in the ankle that involves one or both of the bony protrusions (malleoli)

What is a colles fracture?

• a specific type of broken wrist in which the distal radius (the larger forearm bone near the thumb) breaks and shifts upward toward the back of the hand

What is bones’ role in calcium homeostasis?

• Bones store 99% of the body’s calcium.

• The parathyroid gland secretes Parathyroid hormone (PTH) when calcium levels drop.

• Osteoclasts are stimulated to increase bone resorption and calcium is released.

• PTH also stimulates the production of calcitriol by the kidneys to increase calcium absorption in the intestines.

Describe aging and bone tissue.

• From birth through adolescence, more bone is produced than is lost during remodeling

• In adults, the rates are the same.

• Older individuals, especially post-menopausal women, experience a decrease in bone mass when resorption outpaces deposition.