The Skeletal System

Honors A&P

Do Now:

How would your life be different if you had an exoskeleton (skeleton on the outside)?

Name the bones:1. Frontal 2. Maxillary3. Mandible4. Vertebrae‘5. Clavicle6. Humorous7. Sternum8. Rib9. Radius10.Ulna11. Coxal/pelvic girdle12.Sacrum/coccyx13.Carpals14.Metacarpals15.Phalanges16.Femur17.Patella18.Fibula19.Tibia20.Tarsals21.Metatarsals22.phalanges

Functions Support

Structural support Framework for attachment

Protection Surrounds soft tissues and organs

Storage Calcium and phosphate reserve Energy reserves (triglycerides in yellow marrow)

Hematopoeisis Rbc, wbc, and platelet production in red marrow

Hormone production Osteocalcin – regulates bone formation

Leverage for movement Change magnitude and direction of forces generated by skeletal

muscles Tendons connect muscle to bone

Classification of Bones Axial vs. Appendicular skeletons

Long Bones Longer than they are wide Ex. Limb bones

Short Bones Cube shaped

Ex. Carpals, tarsals Sesamoid bones

Form in tendon Ex. Patella & psiform

Flat Bones Thin and broad Ex. Ribs, sternum, scapulae, ribs, cranial bones

Irregular Bones Complex shapes Ex. Vertebrae and hips

What is NOT part of the Appendicular skeleton?

1 2 3 4 5

20% 20% 20%20%20%1. Hip

2. Scapula

3. Fibula

4. Coccyx

5. Clavicle

What is the tailbone called?

1 2 3 4 5 6 7

14% 14% 14% 14%14%14%14%1. Sacrum

2. Coccyx

3. Patella

4. Scapula

5. Clavicle

6. Hyoid

7. Talus

What is the shin bone called?

1 2 3 4 5 6 7 8

12% 12% 12% 12%12%12%12%12%

1. Sacrum

2. Patella

3. Tibia

4. Fibula

5. Radius

6. Ulna

7. Talus

8. Calcaneous

What type of bone is a rib?

1 2 3 4 5

20% 20% 20%20%20%1. Long

2. Short

3. Flat

4. Irregular

5. Sesmoid

What type of bone is a phalange?

1 2 3 4 5

20% 20% 20%20%20%1. Long

2. Short

3. Flat

4. Irregular

5. Sesmoid

What type of bone is a patella?

1 2 3 4 5

20% 20% 20%20%20%1. Long

2. Short

3. Flat

4. Irregular

5. Sesmoid

What type of bones are the tarsals?

1 2 3 4 5

20% 20% 20%20%20%1. Long

2. Short

3. Flat

4. Irregular

5. Sesmoid

Features of Long Bones Diaphysis

Central shaft of thick collar of compact bone Medullary Cavity

Contains Yellow Bone marrow Loose connective tissue

Compact bone Dense/solid Found in diaphysis

Epiphysis Expanded ends covered w/ articular cartilage Epiphyseal line in adults is remnant of

epiphyseal plate Spongy (cancellous) bone

Network of bony rods w/ spaces Found in epiphysis

Periosteum Covers outer surface of bone w dense irregular

tissue Inner layer osteoblasts and osteoclasts Secured by Sharpey’s fibers (collagen)

Nutirent foramen (formina) Opening in periosteum for bv, nerrves, and lymph

vessles Endosteum

Layer of osteoblasts that lines marrow cavity

Skeletal Cartilage Skeletal Cartilage

Consists of mostly water Avascular, no nerves Surrounded by perichondrium (dense

irregular) w/bv Types

Hyaline Most abundant Articular cartilage , costal cartilage

nasal cartilage, and respiratory cartilage

Elastic External ear & epiglottis

Fibrocartilage Highly copmressable Mensci & vertebral discs

Growth Flexible matrix to accomadate mitosis Appositional growth – from

perichondrium Interstitial growth – from chondrocytes

within

Microscopic Features of Compact Bone

Haversian system (aka osteons) arranged in cylinders

Lamella concentric matrix tube Twister resistor

Haversian (central) canal blood vessels and nerve fibers

Perforating canals (aka Volkmanns canals) connect bv of periosteum to

haversian canal Osteocytes

reside in lacunae Canaliculi

connect lacunae to central canal

Microscopic Features of Bone (cont’d)

Spongy Bone Found in flat, short and irregular bones and

epiphysis of long bones Trabecule (rods create network)

Lamellae arrangemnet No central haversian cancal All 3 bone cell types

In flat bones, the spongy bone is called dipole

Chemical composition Inorganic: 65% mineral salts –

Hydroxyapatite Calcium Phosphates account for hardness

Other 1/3 Osteoid - organic components Cells, collagen, and ground substance

Bone Cytology Osteogenic cells (osteoprogenitor)

bone stem cells Osteoclasts

giant multinucleated cells that secrete acids and enzymes to dissolve bony matrix and release Ca (osteolysis)

Secrete lysosomal enzymes to digest organic matrix and HCl to make Ca soluable

Phagocytic digestion Osteoblasts

produce new bone (osteogenesis) , collagen promotes Ca deposits in bone matrix

Osteocytes Mature bone cells occupy lacunae Monitor and maintain bone matrix Stimulate osteoblasts and osteoclasts

Periosteal and endosteal cells Flat cells on bone surface

Compact Bone vs. Spongy Bone(Ground bone) (Cancellous bone)

Note the absence of osteons in spongy bone

The outer covering of each bone, made from fibrous connective tissue, is called

1 2 3 4 5

20% 20% 20%20%20%1. Epiphysis

2. Diaphysis

3. articular cartilage

4. Periosteum

5. Endosteum

Which cells are responsible for building new osseous tissue?

1 2 3 4 5 6 7

14% 14% 14% 14%14%14%14%1. Osteocytes

2. Osteoclasts

3. Osteoblasts

4. Osteogenic cells

5. Perisoteal cells

6. Endosteal cells

7. Macrophages

Which tissue type houses red bone marrow?

1 2 3 4 5 6

17% 17% 17%17%17%17%1. Compact bone

2. Periosteum

3. Diaphysis

4. Osteon

5. Spongy bone

6. Lamella

Which tissue type has lamellae?

1 2 3 4

25% 25%25%25%1. Compact bone

2. Spongy bone

3. All of the above

4. None of the above

Spongy bone contains all of the following except

1 2 3 4

25% 25%25%25%1. trabeculae.

2. collagen fibers.

3. true osteons.

4. hydroxyapatite

Do Now:

List 4 things in your car…. Complete the following sentence for each

item: A ___(item)____ is like the skeletal system

because_________________

Ossification (Osteogenesis): Bone Formation Begins at 6 weeks (in utero) Composed of fibrous

membranes and hyaline cartilage

Flexible and resilient to accommodate mitosis

Intramembranous Ossification Bone develops within

membranes of connective tissue

Cranial bones & clavicles

Mesenchymal cells form fiberous connective membranes

Endochondrial Ossification

Bone replaces cartilage1. Primary Ossification center –

infiltrated w/bv causing mesenchymal cells to become osteoblasts

2. Bone Collar forms from osteoblasts

3. Chondroctyes within shaft enlarge and calcify and die… opening up a cavity

4. Periosteal bud (bv, nerves, osteoblasts, redmarrow elements) invades internal cavity osteoclasts erode calcified matrix osteoblasts secrete trabeculae

5. Diaphysis elongates – by hyaline cartilage followed by ossification

6. Epiphysis ossify from secondary ossification centers where spongy bone is retained

Bone Growth Post-natal growth of long bones

Cells at epiphyseal plate rapidly divide pushing epiphysis away from diaphysis Cartilage is replaced by bone on diaphysis side, and requires continues remodeling Epiphyseal plate closure occurs at about 18 in females and 21 in males

Growth in width (thickness) Osteoblasts in periosteum secrete bone on external surface as osteoclasts remove bone on the

endosteal surface

Hormonal Regulation Growth hormone (hGH) stimulates growth at epiphyseal plate Sex hormones promote gender specific development of the skeleton

Which of these statements is not true about intramembranous bones?

1 2 3 4

25% 25%25%25%1. They begin with a cartilage model.

2. They form between flat sheets of connective tissue.

3. Skull bones are formed in this way.

4. Osteoblasts deposit new bone along blood vessels within the layers

When cartilage is produced at the epiphyseal side of the metaphysis at the same rate as bone is deposited on the opposite side, bones

1 2 3 4 5

20% 20% 20%20%20%

1. become shorter.

2. become thicker.

3. become more porous and weaker.

4. grow wider.

5. grow longer.

Intramembranous ossification

1 2 3 4

25% 25%25%25%1. is the most common way bones are formed.

2. begins within a connective tissue membrane.

3. is responsible for long bone formation.

4. begins with a cartilaginous precursor.

Osteocytes maintain contact with the blood vessels of the central canal through

1 2 3 4

25% 25%25%25%

1. periosteum.

2. interstitial lamellae.

3. concentric lamellae.

4. canaliculi.

Bone Homeostasis Remodeling

Every week recycle 5-7% of bone mass Spongy bone 3-4 years Compact bone 10 years

Bone deposit occurs at injured or stressed sites Vit C, D,A, Ca, P, Mg, Mn are needed

Bone resorption – osteoclasts Wolf’s Law – bone grows or remodels in

response to the demands placed on it Long bones thickest in middle where bending stress Bony projections where muscles attach Inactivity (even brief) causes atrophy (degeneration)

Prenatal Requirements Prenatal – minerals absorbed from mother (often loses

bone mass) Consume Ca and P from diet Vitamin D3 allows absorption of Ca and P

Vitamin A and C needed for osteoblast activity

Homeostasis and Mineral Storage Calcification – deposition of

calcium salts, regulated by hormones

99% Ca deposited in skeleton Ca+ ions used Nervous &

Muscular System Ca absorbed from intestine

under control of vitamin D Ca ion conc.regulated

Parathyroid hormone (PTH) elevate Ca levels in body fluids

(bones become weaker) Calcitonin

depresses Ca levels in body fluids (bones become stronger)

Injury and Repair Fracture – any crack or break in a bone Healing can take from 4 months to over a year! Fracture hemotoma – large blood clot closes injured bv External and internal calluses – thickenings resulting

from mitotic divisions

Classification of Fractures Displaced (not aligned) or Non-displaced (normal

position)

Complete (through) or incomplete

Linear (parallel) or transverse (perp to bone)

Compound (open sticking through skin) or simple (closed)

Types of FracturesComminuted – 3 or more fragments

Compression – crushed (vertebrae)

Spiral – due to twisting (athletes)

Depression – skull

Greenstick – children (partial break/bend)

http://www.youtube.com/watch?v=usn8ltc1FWU&playnext=2&list=PL27A7948A76FDD768

Fracture Repair Reduction – realignment of broken bone ends

Closed – physician positions bones and immobilizes Open – bones secured w/pins or wires

Hematoma forms Bv rupture and hemmorhage, clot forms, bone cells die

Fibrocartilage callus forms Capillaries grow into hemotoma, phagocytic cells clean area Fibroblasts secrete collagen Chondroblasts secrete matrix, psteoblasts form spongy bone

Bony callus forms Trabeculae appear, endochondrial ossification

Bone remodeling occurs Excess removed, compact bone replaces shaft walls

What is a complete break of a bone and it sticking through the skin?

1 2 3 4 5

20% 20% 20%20%20%1. Dislocation

2. Greenstick

3. Compound Fracture

4. Sprain

5. Simple Fracture

Aging and Skeletal System

Reduction in bone mass occurs between ages 30 -40

Women lose ~8% skeletal mass per decade Men lose ~3% per decade Epiphyses, vertebrae, and jaws most vulnerable Osteoperosis – decrease in estrogen increases

osteoclast activity (so does smoking); other causes include lack of Ca+ in diet, inactive lifestyle, and certain medications

Which of the following factors is NOT believed to affect bone growth?

1 2 3 4 5

20% 20% 20%20%20%1. Exercise and gravity

2. Genetic factors

3. Stimulation by hormones such as growth hormone, testosterone, thyroid hormone, and estrogen

4. Increased intake of protein

5. Diet deficiencies in vitamins D and C, and minerals such as calcium

How would increasing the proportion of organic molecules to inorganic components in the bony matrix affect the physical characteristics of bone?

1 2 3 4 5

20% 20% 20%20%20%

1. The bone would be less flexible.

2. The bones would be more brittle.

3. The bones would be more flexible.

4. The bones would be less compressible.

5. The bones would be stronger.

Mary is 50 years old. During a checkup, a bone scan reveals that portions of her skeleton show signs of osteoporosis. Her physician suggests hormone therapy after reviewing the test results. What hormone is prescribed for Mary?

1 2 3 4

25% 25%25%25%

1. Parathyroid hormone

2. Calcitonin

3. Estrogen

4. Growth hormone

Bone Markings

Bone Markings