Ch 7- Bone Tissue

Bones, cartilage, and ligaments, which form the body’s framework.

What are the main components of the skeletal system?

osteology

The study of bones.

• Cartilage covers joint surfaces and forms most bones during development

• ligaments connect bones at joints.

What is the role of cartilage and ligaments in the skeletal system?

Tendons attach muscles to bones; ligaments attach bones to bones.

What is the difference between tendons and ligaments?

• Support the body

• protect organs

• enable movement

Name three major functions of bones in the body.

Regulate electrolyte balance, buffer blood pH, produce blood cells, and secrete hormones.

what other roles do bones play besides support, protection, and movement?

osseous tissue

Connective tissue with a matrix hardened by calcium phosphate and other minerals.

mineralization (calcification)

the process of hardening bone by depositing minerals in its matrix.

Flat – sternum

Long – femur

Short – wrist bones

Irregular – vertebrae

Name the four bone shapes and one example of each.

Compact bone is dense and forms the outer shell; spongy bone is lighter, loosely organized, and found inside ends and shafts of bones.

What is the difference between compact and spongy bone?

Diaphysis

shaft of a long bone

Epiphysis

enlarged ends

Epiphyseal line

remnant of childhood growth plate.

articular cartilage

Hyaline cartilage covering joint surfaces, allowing smooth movement.

Periosteum

outer bone sheath with fibrous and osteogenic layers

Endosteum

thin layer lining marrow cavity and internal surfaces.

Two layers of compact bone with spongy bone (diploe) in between.

What is the structure of flat bones?

• Osteogenic – stem cells that produce osteoblasts

• Osteoblasts – build bone

• Osteocytes – maintain bone and sense stress

• Osteoclasts – dissolve bone

Name the four types of bone cells and a primary function of each.

• One-third organic (collagen/proteins) for flexibility,

• two-thirds inorganic (hydroxyapatite, calcium carbonate) for strength.

What is the bone matrix made of, and why is it important?

• Mineral deficiency → rickets (soft bones)

• Collagen defect → osteogenesis imperfecta (brittle bones)

What happens if bone lacks minerals or collagen?

Osteon

structural unit of compact bone, includes concentric lamellae surrounding a central canal;

• perforating canals connect osteons.

Helical arrangement in opposite directions strengthens bone and prevents fracture spread.

How does collagen orientation in lamellae help bone?

circumferential lamellae

layers encircling bone inner/outer regions

interstitial lamellae

fill spaces between osteons

Spongy bone has a lattice of spicules and trabeculae covered with endosteum; it is lightweight but strong, with spaces filled with red bone marrow.

What is spongy bone made of and what is its function

Trabeculae develop along lines of stress to provide strength where needed.

How does spongy bone relate to mechanical stress?

Red marrow produces blood cells; yellow marrow is fatty and does not produce blood but can revert to red marrow if needed.

What is the difference between red and yellow bone marrow?

Skull, vertebrae, ribs, sternum, parts of the pelvic girdle, and proximal heads of humerus and femur

Where is red marrow found in adults?

ossification (osteogenesis)

The formation of bone from embryonic mesenchyme.

Flat bones of the skull, most clavicles, and part of the mandible.

What bones are formed by intramembranous ossification?

1. Osteoid deposition

2. Calcification

3. Spongy bone forms

4. Compact bone forms at surfaces

What are the stages of intramembranous ossification?

Most bones of the body, including limbs, vertebrae, ribs, sternum, scapula, and pelvic girdle.

What bones are formed by endochondral ossification?

1) Cartilage model forms

2) Primary ossification center forms

3) Vascular invasion and marrow cavity

4) Secondary ossification center forms

5) Epiphyseal plate present in children

6) Epiphyseal line forms in adults

What are the stages of endochondral ossification?

It serves as the growth zone where cartilage is replaced by bone, allowing bones to lengthen.

What is the role of the epiphyseal plate in bone growth?

appositional growth

Growth in bone diameter and thickness by adding tissue at the surface; osteoblasts deposit bone, osteoclasts enlarge marrow cavity.

Wolff’s law of bone

Bone structure adapts to mechanical stress; bones grow stronger where stressed.

mineral deposition

Osteoblasts deposit calcium, phosphate, and other minerals into bone to harden it.

mineral resorption

Osteoclasts dissolve bone, releasing minerals into the blood.

Osteoclasts dissolve bone in front of the tooth, and osteoblasts deposit bone behind it.

How do braces move teeth using bone remodeling

Needed for bone structure, nerve communication, muscle contraction, blood clotting, and exocytosis.

Why is calcium important in the body?

Hypocalcemia

low blood calcium, causing overactive nerves/muscles

Hypercalcemia

high blood calcium, causing less excitable nerves/muscles.

• Calcitriol

• calcitonin

• parathyroid hormone (PTH)

What three hormones regulate calcium homeostasis?

1) Increases calcium absorption in small intestine

2) stimulates osteoclast formation for bone resorption

3) weakly increases kidney calcium reabsorption

How does calcitriol (vitamin D) increase blood calcium?

• It provides adequate calcium and phosphate for mineralization

• deficiency causes rickets in children and osteomalacia in adults.

Why is calcitriol important for bone deposition?

inhibits osteoclasts (reducing bone resorption) and stimulates osteoblasts to deposit calcium into bone.

How does calcitonin lower blood calcium?

in children; weak effect in adults. May help prevent bone loss in pregnancy/lactation.

When is calcitonin most effective?

1) Stimulates osteoclasts via osteoblasts

2) increases kidney calcium reabsorption

3) promotes calcitriol formation

4) inhibits collagen synthesis by osteoblasts

How does parathyroid hormone (PTH) raise blood calcium?

Calcitriol increases intestinal phosphate absorption; PTH promotes phosphate excretion in urine.

How is phosphate homeostasis regulated?

Hormones like growth hormone, estrogen, testosterone; vitamins and growth factors; sex, age, and anabolic steroids.

What factors affect bone growth besides calcium?

Stress fracture

caused by abnormal trauma.

Pathological fracture

caused by normal stress on weakened bone (e.g., osteoporosis, cancer).

1) Hematoma formation

2) soft callus formation

3) hard callus formation

4) bone remodeling

What are the four stages of fracture healing?

• Closed reduction: realignment without surgery.

• ORIF: surgical exposure with plates, screws, or pins.

What is the difference between closed reduction and ORIF for fractures?

osteopenia

Measurable decline in bone density that may progress to osteoporosis.

osteoporosis

Severe loss of bone density causing easily fractured bones; women, small/light frames, older age

• White women of Asian/European descent are most vulnerable.

• Assessed with bone densitometry (DEXA scan)

• prevented with weight-bearing exercise and treatments that stimulate bone deposition or slow resorption.

How is osteoporosis assessed and prevented?