skeletal system

SKELETAL SYSTEM

History During the Renaissance (Rebirth) the study of human life and medicine began to flourish. Scientist, Doctors, and Artist would experiment and practice on the dead and incarcerated. Cadavers were positioned flat on their backs, thus making it easier to draw and reference from that position. Many artist such as Leonardo da Vinci or Madam Tussuads began to study, draw, and diagram the human body.

FUN FACTS ABOUT BONES Bone is made of the same type of minerals as limestone. Babies are born with 300 bones, but by

adulthood we have only 206 in our bodies. The giraffe has the same number of bones in

its neck as a human: seven in total. The long horned ram can take a head butt at

25 mph. The human skull will fracture at 5mph.

The Skeletal System

Parts of the skeletal system includes: Bones, joints, cartilage, ligaments, and tendons

Divided into two main divisions: Axial skeleton head, neck, and trunk Appendicular skeleton limbs and girdle

Support

Protection of soft parts

Allows for movement by attaching to muscles

Triglycerides and growth factor storage

Blood cell formation (bone marrow) and hormone production hematopoiesis

Storage of inorganic materials

(salt, calcium, potassium, phosphate and fat.)

What are the func,ons of the skeletal system? Bones are made of OSSEOUS TISSUE

Classification of Bones on the Basis of Shape

Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 5.1

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 (joints)

Yellow bone marrow stores fat Red bone marrow makes blood

cells found in spongy bone and flat bones

Periosteum outer covering of fibrous connective tissue ( blood vessels)

Ligaments fibrous connective tissue that connects bones

blood vessel

periosteum

compact bone

growth plate

hyaline cartilage (articular cartilage)

spongy bone (contains red bone marrow)

medullary cavity (contains yellow bone marrow)

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Anatomy of 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

Compact bone

osteocytes in lacunae

spongy bone

osteon

blood vessels

central canal

osteocyte lacuna nucleus

canaliculus Osteocyte

100 m

concentric lamellae

osteocyte in lacuna


Chemical Composi,on of Bone

Osteoid (organic bone matrix)

Mineral salts

Cells

What are the important cells in bone growth, remodeling and repair?

Osteogenic cells: stem cells

Osteoblasts : bone-forming cells

Osteocytes : mature bone cells that maintain bone structure derived from osteoblasts. (Enclosed in tiny chambers called lacunae)

Bone lining cells: produce the periosteum

Osteoclasts bone-absorbing cells

Chondrocytes cartilage-forming cells

RESORPTION OSTEOCLASTS - dissolve bone tissue to release minerals, process is called RESORPTION

How does bone develop?

11.2 Bone growth, remodeling and repair

Ossica,on Or Osteogenesis Process of bone 8ssue forma8on

Forma8on of bony skeleton Postnatal bone growth Bone remodeling and repair

Embryonic skeleton:

fashioned from fibrous membranes or cartilage to accommodate mitosis.

Two types of pre-natal ossica,on (bone forma,on)

1. Intramembranous Bone develops from fibrous membrane Forms bones of skull and clavicle (all flat

bones) Begins 2nd month of development

2. Endochondral Bone develops from hyaline

cartilage Forms all bones below base of skull Begins 2nd month of development

Fetus At Twelve Weeks

How does endochondral ossification occur?

Endochondral Ossification

Bone collar formed around diaphysis by osteoblasts located on inner side of periosteum

1st Cartilage model chondrocytes lay down hyaline cartilage in the shape of the future bones

2nd Bone collar formation osteoblasts secrete bone matrix and results in a collar made of compact bone

Week 9


Cartilage in primary ossification center calcifies, then the cells die and cavities form (cavitates)

Bone collar provides stability during cavitation

Cartilage elsewhere continues to elongate

Week 9


Periosteal bud (lymph, blood vessels, nerves, red marrow, osteoblasts and osteoclasts) enters cavity and builds spongy bone

3rd Primary ossification center osteoblasts are brought interiorly by blood and lay down spongy bone

Month 3


Osteoclasts dissolve spongy bone to create medullary cavity

Secondary Ossification Center forms in epiphysis

4th Secondary ossification sites bone centers in the epiphyses formed after birth

Birth


Secondary Ossification Center does NOT calcify. Spongy bone retained.

Hyaline only remains on epiphyseal surface (articular cartilage) and at diaphysis and epiphysis junction, to form the epiphyseal plates.

5th Epiphyseal plate a cartilage band that acts as a growth plate that allows bones to lengthen

Childhood Adolescence

Visualizing endochondrial ossification

Postnatal Bone Growth

Inters88al (longitudinal) growth Increase in length of long bones

Apposi8onal growth Increase in bone thickness

Growing Taller! (A closer look at the epiphyseal plate)

Lots of activity! rapidly mitotic cartilage, lengthening bone; chondrocytes form columns

enlarging size of chondrocytes (hypertrophy)

matrix of cartilage calcifies and cells die forming spiky tips

spiky calcified cartilage reshapes into spongy bone, converted into medullary cavity or compact bone later as bone grows.

When does lengthening stop?

End of adolescence - lengthening stops Chondrocytes stop mitosis. Plate thins out and replaced by bone Diaphysis and epiphysis fuse to be one bone

Epiphyseal plate closure (18 yr old females, 21 yr old males)

Thickening of bone continuous throughout life

What is bone remodeling and what is its role in homeostasis?

Bone remodeling bone renewal at a rate of up to 18% per year

Spongy bone replaced every 3-4 years and compact bone replaced every 10 years

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

Bone Remodeling

Bone Remodeling Homeostasis

Importance of Calcium

Nerve impulse transmission

Severe neuromuscular problems

Hypercalcemia To much calcium

How do hormones affect bone growth?

Growth hormone (GH) stimulates general bone growth and the epiphyseal plates

Thyroid hormone moderates growth hormone Testosterone (males) and estrogens (females) at

puberty. Sex hormones increases growth during adolescence (growth spurt)

Vitamin D converted to a hormone to allow calcium absorption in the intestine

Bone repair hematoma

medullary cavity

periosteum fibrocartilaginous callus

spongy bone 1. Hematoma 2. Fibrocartilaginous

callus healed fracture

3. Bony callus 4. Remodeling

bony callus

a. b.


b: Tony Freeman/PhotoEdit

compact bone

(6-8 hours) (3 weeks)

(3 -4 months) (Bone Remodeling Occurs)

Science focus: Skeletal remains

Characteristics to be determined:

1. Age: approximated through dentition, studying areas of bone ossification and joint condition

2. Gender: pelvic bone is best used, thickness of long bones, skull characteristics

3. Ethnicity: difficult to tell but skull characteristics are most useful

Iden8fying Skeletal Remains

http://www.youtube.com/watch?v=mfi6gOX0Nf4

206 bones in human skeleton Divided into two groups:

Axial (80 bones) Head, Neck , and Trunk

Appendicular (126 bones)- Pectoral & Pelvic Girdle

Classica,on Of Bones

The Axial Skeleton: The Skull

The Axial Skeleton: The Hyoid Bone

The hyoid bone is a visceral organ that is aXached by ligaments

Func8ons include: holding up the tongue and the larynx and it transmits the force of muscles that help open the jaw

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


1

1

1

2

2

2

3

3

3

4

4

4

5

5

5

6

6

7

7

8

9

10

1 1

12

5 lumbar vertebrae in small of back form lumbar curvature.

Sacrum: 5 fused vertebrae in adult form pelvic curvature. Coccyx: usually 35 fused vertebrae form the tailbone.

intervertebral disks

transverse process of vertebra

intervertebral foramina

rib facet of vertebra (only on thoracic vertebrae)

spinous process of vertebra

7 cervical vertebrae in neck region form cervical curvature.

12 thoracic vertebrae form thoracic curvature. Ribs attach here.

The Axial Skeleton: 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


sternum

floating ribs

costal cartilage

b.

superior articular facet for a vertebra

Appendicular Skeleton: Pectoral Girdle

Pectoral girdle Scapula and Clavicle

Upper limb Arm Hand bones


Appendicular Skeleton: Pelvic Girdle

Pelvic girdle coxal bone

Lower limb Leg and foot bones


metatarsals phalanges

tarsals

medial malleolus lateral malleolus

tibia

tibial tuberosity

femur

medial condyle patella (kneecap)

head of femur

acetabulum

fibula

head of fibula

lateral epicondyle

greater trochanter

lesser trochanter

coxal bone

The 206 bones of the skeleton Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Skull: frontal bone zygomatic bone maxilla mandible

Pectoral girdle: clavicle scapula

Rib cage: sternum ribs costal cartilages

vertebral column

sacrum coccyx

carpals metacarpals

phalanges

patella

tarsals

parietal bone temporal bone occipital bone

scapula humerus

ulna radius

femur

metatarsals phalanges

Skull:

a. b.

clavicle

fibula

tibia

Pelvic girdle: coxal bones

Diseases and Conditions of the Skeletal System

Video Watch

CHAPTER 11 SKELETAL SYSTEM 1. Dene the following terms: diaphysis, epiphysis, ar8cular car8lage, chondrocytes, red bone marrow, periosteum, medullary cavity, yellow bone marrow, epiphyseal growth plate, osteon, central canal, canaliculi,

lacunae, lamellae, ossica8on, inters88al growth, apposi8onal growth, axial skeleton and appendicular skeleton. 2. Describe the structures located in the skeletal system. 3. Describe the func8ons of the skeletal system. 4. Describe the structure of a long bone. 5. Describe the structural dierences between compact and spongy bone. 6. Describe the chemical composi8on of bone. 7. Describe the ve types of cells found in bone 8ssue. 8. Describe the dierences between intramembranous and endochondral ossica8on. 9. Provide examples of where intramembranous ossica8on occurs and where endochondral ossica8on occurs. 10. Describe the structure and func8on of the four layers of the epiphyseal plate. 11. Describe the process of bone remodeling. 12. Describe the importance of bone remodeling in the human body. 13. Describe the func8on of growth hormone, thyroid hormone, estrogen, testosterone, parathyroid hormone and calcitonin. 14. Describe the four steps involved in bone repair. 15. Iden8fy and describe the major bones of the axial and appendicular skeleton. 16. How are age, gender and ethnicity determined through skeletal remains?

skeletal system

Documents

bones bone

anatomy of bone compact

bone structure

living bone cells

mature bone cells

lacunae bone lining

yellow bone marrow copyright

blood cells