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Chapter 11. What are the functions of the skeletal system? More detail on bone

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Chapter 11

Skeletal System

What are the functions of the skeletal

system?

1. Supports the body

2. Protects the soft body parts

3. Produces blood cells

4. Stores minerals (calcium and phosphate)

and fat

5. Allows for movement by attaching

muscles

11.1 Overview of the skeletal system

What is the anatomy of a long bone?

• Diaphysis – shaft of the bone made of compact bone and filled with yellow marrow

• Epiphysis – ends of the bone made mostly of spongy bone • Articular cartilage – hyaline cartilage

found on the ends of long bones • Yellow bone marrow – stores fat • Red bone marrow – makes blood cells

found in spongy bone and flat bones • Periosteum – living, outer covering of

fibrous connective tissue • Ligaments – fibrous connective tissue

that connects bones

11.1 Overview of the skeletal system

More detail on bone…

• Compact bone

– Composed of osteons with a central canal containing blood vessels

– Contains living bone cells called osteocytes chambers called lacunae

• Spongy bone

– Made of plates with spaces filled with red bone marrow

(2)

Where are the 3 types of cartilage found?

• Cartilage – flexible connective tissue

categorized based on the type and arrangement

of matrix fibers

• Types:

– Hyaline cartilage – ends of long bones, nose, ends of ribs, larynx and trachea

– Fibrocartilage – disks between vertebrae and in the knee; stronger than hyaline cartilage

– Elastic cartilage – ear flaps and epiglottis; more flexible than hyaline cartilage

11.1 Overview of the skeletal system

What are the important cells in bone growth,

remodeling and repair?

• Osteoblasts – bone-forming cells

• Osteocytes – mature bone cells that

maintain bone structure derived from

osteoblasts

• Osteoclasts – bone-absorbing cells

11.2 Bone growth, remodeling and repair

How does bone develop?

Ossification - the formation of bone in two

distinct ways:

1. Intramembranous ossification - bone

development between sheets of fibrous

connective tissue; used in flat bones

2. Endochondrial ossification – cartilage is

replaced by bone; used by most bones

11.2 Bone growth, remodeling and repair

How does endochondral ossification occur?

1stCartilage model – chondrocytes lay down hyaline cartilage in the

shape of the future bones

2ndBone collar formation – osteoblasts secrete bone matrix and results

in a collar made of compact bone

3rdPrimary ossification center – osteoblasts are brought interiorly by

blood and lay down spongy bone

4thSecondary ossification sites – bone centers in the epiphyses formed

after birth

5thEpiphyseal plate – a cartilage band that acts as a growth plate that

allows bones to lengthen

(3)

Visualizing endochondral ossification

11.2 Bone growth, remodeling and repair

How do bones lengthen?

11.2 Bone growth, remodeling and repair

How do hormones affect bone growth?

• Growth hormone (GH) – stimulates

general bone growth and the epiphyseal

plates

• Sex hormones – increases growth during

adolescence

• Vitamin D – converted to a hormone to

allow calcium absorption in the intestine

11.2 Bone growth, remodeling and repair

What is bone remodeling and what is its

role in homeostasis?

• Bone remodeling – bone renewal at a rate of up

to 18% per year

• Remodeling allows bones to respond to stress

• Regulates the calcium in the blood through

hormones:

– Parathyroid hormone (PTH) – increases blood calcium by accelerating bone recycling – Calcitonin – decreases blood calcium

(4)

Health focus: Osteoporosis

• Osteoporosis – bones are weakened due to a decreased bone mass

• Bone reabsorption exceeds absorption usually by age 40

• Risk factors: women, white or Asian, thin, family history, early menopause, smoking, diet low in calcium, excessive caffeine or alcohol consumption and a sedentary lifestyle

• Can lead to fractures and other complications

• Can be treated with drugs, hormones and lifestyle change

11.2 Bone growth, remodeling and repair

Steps in bone repair

• Hematoma (6-8 hrs.) – blood clot formed between broken bones

• Fibrocartilaginous callus (~ 3 weeks) – cartilaginous callus forms between broken bones

• Bony callus (3-4 months) – cartilaginous callus is turned to bone

• Remodeling – old bone tissue is replaced by new bone tissue

11.2 Bone growth, remodeling and repair

Bone repair

11.2 Bone growth, remodeling and repair

The 206 bones of the skeleton

(5)

The axial skeleton

• Skull – made of cranium and facial bones

• Hyoid bone

• Vertebral column – vertebrae and

intervertebral disks

• Rib cage – ribs and sternum

11.3 Bones of the axial skeleton

The skull – the cranium

• Cranium

– Protects the brain – Composed of 8 bones – Some contain sinuses

11.3 Bones of the axial skeleton

Bones of the face and the hyoid bone

• Facial bones

– Mandible – Maxillae – Zygomatic bones – Nasal bones

• Hyoid

– Only bone that does not articulate with another bone

11.3 Bones of the axial skeleton

The vertebral column

• Types of vertebrae

– 33 vertebrae • Cervical (7) • Thoracic (12) • Lumbar (5) • Sacrum (5 fused) • Coccyx (4 fused into

tailbone)

• Intervertebral disks

– Fibrocartilage between vertebrae

(6)

The rib cage

• Ribs – protects heart and

lungs

– Flattened bone originating from the thoracic vertebrae – 12 pairs:

• 7 pr. true ribs • 3 pr. false ribs • 2 pr. floating ribs

• Sternum

– Known as the breastbone

11.3 Bones of the axial skeleton

The appendicular skeleton

• Pectoral girdle

– Scapula and clavicle

• Upper limb

– Arm and hand bones

11.4 Bones of the appendicular skeleton

The appendicular skeleton

• Pelvic girdle

– coxal bone

• Lower limb

– Leg and foot bones

11.4 Bones of the appendicular skeleton

Types of joints

(where bones meet bones)

• Fibrous – usually immovable such as the

sutures between cranial bones

• Cartilaginous – tend to be slightly movable

such as the intervertebral disks

• Synovial – freely movable joints such as

the ball-and-socket hip and shoulder joints

and the knee joint

(7)

Anatomy of a synovial joint

11.5 Articulations

Summary of synovial joints movements

• Flexion – decrease in joint angle

• Extension - increase in joint angle

• Adduction – body part moves toward midline

• Abduction – body part moves away from midline

• Inversion – sole of foot turns inward

• Eversion – sole of foot turns outward

11.5 Articulations

Visualizing synovial joints movements

References

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