Human%20Anatomy

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Human Anatomy

• Skeletal System

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Functions

• Support body structure and shape
• Protection for vital organs (brain, heart, etc.)
• Movement for attached skeletal muscles
• Tendons attach muscle to bone
• Ligaments attach bone to bone
• Mineral storage calcium and phosphorus
• Blood cell formation - hematopoiesis

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Types of Bone
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Compact Bone

• Very dense, stress bearing
• Haversian systems basic unit
• of compact bone
• Lamellae concentric cylinder
• shaped calcified structure
• Lacunae small spaces
  containing tissue fluid
• Osteocytes facilitate exchange
  of calcium between blood and bone
• Canaliculi canals connecting the lacunae
  together and to the haversian canal which carries
  nutrients and wastes to and from the osteocytes
  

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Cancellous Bone

• Light, spongy
• Found at ends of long bones, ribs, sternum, hips,
  vertebrae, cranium
• No haversian systems
• Web-like arrangement
• Highly vascular

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• Classification of Bones

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Long bones

• Found in the extremities
• Act as levers
• Includes
• Epiphysis
• End of long bones
• Covered with hyaline cartilage for articulation
• Filled with cancellous bone
• Diaphysis
• Shaft
• Covered with periosteum
• Medullary canal
• Compact bone
• Examples femur, tibia, fibula, humerus,
• radius, clavicle, metacarpals, phalanges

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Short Bones

• Cube shaped
• Allows flexible movement
• Cancellous bone covered by compact bone
• Examples
• Carpals
• Tarsals
•  

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Flat Bones

• Protect vital organs and provide broad surface
  area for muscle attachment
• Examples
• Cranial bones
• Scapula
• Sternum
• Ribs

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Irregular Bones

• Peculiarly shaped to provide support and
  protection, yet allow flexibility
• Examples
• Vertebrae
• Ear
• Hyoid
• Mandible

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Sesamoid Bones

• Extra bones found in certain tendons
• Example
• Patella
•  

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Composition

• Collagen chief organic constituent (protein)
• Inorganic calcium salts (Vitamin D essential for
  absorption of minerals i.e. calcium)
• Deposition favored by
• a. Estrogen, testosterone
• b. Alkaline phosphatase
• c. Thyrocalcitonin
• d. Mechanical stress i.e. traction
• Withdrawal favored by
• a. Alkaline phosphatase
• b. Parathormone
• c. Inactivity

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Composition

• Cells
• Osteoblasts bone building, bone repairing cells
  in the periosteum
• Osteocytes mature bone cells within the bone
  matrix
• Osteoclast causes reabsorption of bone
• Periosteum
• 1. Dense, fibrous membrane covering bone
• 2. Contains blood vessels
• 3. Essential for bone cell survival and bone
  formation
•  

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Cells that Aid in Bone Formation
Builds new bone
Osteoblast
Mature bone cell
Osteocyte
Osteoclast
Eats bone
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Bone Formation

• Initially collagen fibers secreted by fibroblasts
  
• Cartilage deposited between fibers
• Skeleton fully formed by 2nd month of fetal
  development (all cartilage)
• After 8th week of fetal development ossification
  (mineral matter deposited and replaces cartilage)
  begins
• Childhood and adolescence
• ossification exceeds bone loss
• Early adulthood thru middle age
• ossification equals bone loss
• After age 35
• bone loss exceed ossification

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275 bones12 weeks (6-9 inches long)
Fetal Skeleton
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Anatomy of Long Bone

• Diaphysis
• Shaft
• Composed of compact bone
• Epiphysis
• Ends of bone composed mostly
• of spongy bone
• Periosteum
• outside covering of diaphysis
• Endosteum
• Lines medullary cavity
• Arteries
• Articular cartilage
• Medullary cavity
• Cavity inside the shaft
• Contains yellow marrow (mostly fat) in adults

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Bone Marrow

• Red bone marrow
• Found in vertebrae, ribs, sternum, cranium, ends
  of humerus and femur
• Produces
• Erythrocytes red blood cells
• Plateletes - thrombocytes clotting cells
• Some leukocytes white blood cells
• Yellow bone marrow
• Found in medullary cavity of long bones
• Fat storage

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Bone Marrow

• Yellow marrow
• Medullary cavity of long bones
• Fat storage
• Red marrow
• Hematopoietic tissue
• In all cancellous bone in children
• In adults cancellous bone of vertebrae, hips,
  sternum, ribs, cranial bones, proximal ends of
  femur and humerus
• Forms RBCs, platelets, some WBCs, and destroys
  old RBCs and some foreign materials

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Divisions of the Skeletal System
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Axial Skeleton

• Forms the longitudinal axis of the body
• Divided into three parts
• Skull
• Vertebral Column
• Thorax

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Appendicular Skeleton

• Composed of 126 bones
• Includes bones of the
• Limbs (appendages)
• Pectoral (shoulder) girdle
• Pelvic (hip) girdle

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Joints
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Classification

• Synarthrotic immovable - cranium
• Amphiarthrotic limited movement i.e. pubic
  symphysis, vertebral joints, sacroiliac joint
• Diarthrotic freely movable
• Gliding bones of the wrist
• Pivot between radius and ulna
• Ball and socket hip
• Hinge elbow

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Immovable Joints Synarthrosis
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Slightly Movable Joint Ampharthrosis
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Freely Movable Diarthrosis
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Synovial Joint Movement
Extension
Rotation
Flexion
Adduction
Abduction