Skeletal System Overview
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Transcript of Skeletal System Overview
Skeletal System
OverviewChapter 7
p. 192 – p. 204
What makes up bone?
Osteocytes (bone forming cells) and extracellular matrix Osteocytes are found in lacunae
(holes in the bony matrix) Extracellular matrix is made up of
collagen and inorganic salts (nonliving)
What tissues are associated with bone?
What tissues are associated with bone?
Cartilage Dense connective tissue Blood Nervous tissue
Types of Bones
Long bones Short bones Flat bones Irregular bones Sesamoid bones
Long Bones Epiphysis Articular Cartilage Diaphysis
Spongy bone Compact bone
Parts of the Long Bone Periosteum
Vascular, fibrous outer covering of bone
Endosteum Lines medullary cavity Contains bone forming cells
Medullary Cavity Hollow region of bone Continuous with the spongy bone Marrow, blood vessels found here Adults: yellow marrow
Spongy Bone Trabeculae: branching bony
plates Space between the bony
plates allows for cushion
Spongy bone is usually found at the ends of long bones
In adults: red marrow found here
Compact Bone
Made up of osteons Circular units with central blood vessels
and nerves Also called Haversian systems Resists compression Run parallel with the diaphysis Canaliculi connect osteocytes
Allow for the transport of nutrients and waste
Compact Bone
Made up of osteons Circular units with central blood vessels
and nerves Also called Haversian systems Resists compression Run parallel with the diaphysis Canaliculi connect osteocytes
Allow for the transport of nutrients and waste
Volkmann’s canals Also known as perforating canals Contain blood vessels and nerves Communicate with surface of the bone Run perpendicular to the diaphysis
Osteon
Volkmann’s Canals
Short Bones Make up hands and feet
Flat Bones Scapula (shoulder blade) Skull Ribs
Irregular Bones Vertebrae Facial bones
Sesamoid Bones
Not always a separate category
Round bones Patella
Bone Marrow
Bone Development
Osteogenesis: development of bone Intramembranous Bone (flat bones)
Unspecialized cells appear at site of new bone formation
Blood vessels move into these cells and allow cells to differentiate into osteoblasts Deposit bony matrix to form
spongy bone Spongy bone would fill in with
higher amounts of bony matrix to form compact bone
Bone Development
Endochondral Bones Develop from masses of hyaline
cartilage Hyaline cartilage lays down basic bone
layout Over time, bone forms over the cartilage
template Osteoblasts form and secrete bony
matrix Once bony matrix surrounds the
osteoblasts, they are called osteocytes Endochondral ossification
Bone Development
Primary ossification center Bone begins to replace hyaline
cartilage in the diaphysis Osteoblasts in periosteum deposit
compact bone Secondary ossification centers
Epiphyses Spongy bone
Epiphyseal plate – zone of cartilage between diaphysis and epiphysis
Bone Development
Growth at the Epiphyseal Plate 4 layers
Resting cartilage No growth Closest to the epiphysis
Proliferating cartilage Young cells, mitosis
Zone of hypertrophic cartilage Older cells
Zone of calcified cartilage Dead cells and extracellular
matrix
Growth at the Epiphyseal Plate
http://www.gla.ac.uk/ibls/US/fab/tutorial/generic/bone5.html
Osteoclasts
Invade areas of calcified cartilage Break down extracellular matrix Osteoblasts then move in
Deposit bony matrix in place of calcified cartilage
Ossification Timetable (p. 200)Age Occurrence3rd month of prenatal development
Ossification of long bones begins
4th month of prenatal development
Primary ossification centers are present in long bones
Birth to 5 years Secondary ossification centers present
F: 5-12 years; M: 5-14 years Ossification rapid through ossification centers
F: 15-18 years; M: 17-20 years Bones of upper limb/scapulae completely ossified
F: 16-20 years; M: 18-23 years Lower limbs and hips completely ossified
F: 21-23 years; M: 23-25 years Sternum, clavicles, vertebrae completely ossified
F: by 23; M: by 25 Nearly all bones are completely ossified
Bones under the microscope
Osteoporosis
Stages of Human Bone Development
Infant
Less than one year old Approximately 300 bones (small bones
have not fused yet) Skull much larger than body
Bones are not fused Smaller pelvis
Toddler
1 – 2 years Begin teeth growth Ossification of bones
Youngster
Ages 3 – 9 Bones complete fusion Cervical vertebrae thicken Lower jaw thickens Skull becomes rounder, less elongated Increase in teeth number Ribs ascend Pelvis broadens
Youth
Ages 10 – 13 Angular jaw More teeth Longer neck Sacrum shorter Fibula separates farther from tibia
Adolescent / Young Adult
Ages 14 – 25 pelvis wider at the top Rib cage elongates Vertebrae thicken Growth plates close
Adult
26+ Mature bones Back curves Sharp ridges on neck Rough edges on bone
High amounts of deposits Hip angle increases (more triangular) Heel bone extends Vertebrae begin to shrink
Adult with Osteoporosis
Vertebrae shrink Pronounced curvature of
the back Bone becomes brittle,
breaks easily
Skull Development
Work with a partner to answer the following question:
How does the skull change from birth to adulthood? Why?
Summarize the changes in each stage of life.
Factors Effecting Bone Growth and Repair
Nutrition Exposure to sunlight Hormones Physical exercise
Work with a partner to research a factor effecting bone growth and it’s effect on development
Look up a bone growth disorder, too. (Brief!)
Fractures
Greenstick – incomplete, across bone (usually in developing bone)
Fissured – incomplete, longitudinal Comminuted – complete, shatters the bone Transverse – complete, right angle to bone
axis Oblique – at an angle other than a right
angle Spiral – caused by excessive twisting of the
bone Compound – bone breaks the skin
Fractures
Bone Repair
Hematoma forms (blood released from vessels within the bone)
Formation of spongy bone and fibrocartilage
Bony callus Osteocytes, osteoblasts and
osteoclasts
Functions of the Skeletal System
Support and Protection Movement
Origin and insertion of muscle Origin: immovable end of the muscle Insertion: movable end – during
contraction, insertion will move toward the origin
Functions of the Skeletal System
Blood production Hematopoiesis Bone marrow – long
bones, spongy bone, larger canals of compact bone
Red marrow: produces red blood cells, white blood cells and platelets
White marrow: fatty tissue
Functions of the Skeletal System
Inorganic salt storage Salts account for approximately 70%
of extracellular matrix of bone Mostly calcium phosphate –
hydroxyapatite Also: magnesium, sodium,
potassium, carbonate ions Will also absorb small amounts of
harmful metallic elements (lead, strontium)