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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
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
Endochondral Ossification
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
Endochondral Ossification
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
Endochondral Ossification
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
Endochondral Ossification
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
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.
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
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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
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Appendicular Skeleton: Pelvic Girdle
Pelvic girdle coxal bone
Lower limb Leg and foot bones
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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?