Skeletal System

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Skeletal System
300 baby bones 206 adult bones gt1/2 in hands
feet Humans giraffes have same neck
bones Longest bone femur Smallest bone inner
ear (hammer, anvil, stirrup)
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Functions of Skeletal System

• Support
• Protection
• Movement
• Hematopoiesis
• Reservoir for minerals and adipose tissue

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Skull 22 bones Cranium 8 Facial - 14
Vertebral Column - 32
Inner ear - 3
Thorax - 27
Iliac crest
80 bones
Upper limb 30 Shoulder girdle - 2
Lower limb 29 Pelvic girdle 6
126 bones
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Thoracic Cage27 bones
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Vertebral Column32 bones
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Abnormal Spinal Curvatures
Lordosis Kyphosis Scoliosis
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The Hand27 bones
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The Foot26 bones
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Arches of the Foot
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The Skull 22 bones
Foramen For nerves and vessels
keystone of cranium
Ethmoid
Ethmoid
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Suture - Fibrous joint
Process - projection that contacts adjacent bone
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Infant Skull
closes at 8 wks
closes at 9-18 mths
Fontanel space between infant skull bones
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Sinus Cavities
Sinus air-filled space
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Compact Spongy Bone
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Compact Bone
canaliculi
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Bone Classification
Flat
Long
Scapula Sternum Ribs Skull
Arms Legs Phalanges
Short
Irregular
Wrist Ankle
Vertebrate Hip Patella
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Anatomy of Long Bones
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Anatomy of Short, Flat Irregular Bones
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Osteon Structural and functional unit of bone

• Haversion Canal
• Allows passage of blood vessels, lymphatic
  vessels, and nerve fibers
• Lamella
• Concentric rings of collagen fibers around
  haversion canal
• Allows bone to withstand force
• Lacunae
• Small cavities occupied by osteocytes that join
  lamella
• Canaliculi
• Hairlike canals that join lacunae to each other
  and the central canal
• Allow osteocytes to exchange nutrients, wastes,
  and chemical signals via gap junctions

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Type of Cells in Bone

• Osteoblast
• Build bone cells
• Synthesize and secrete organic components of bone
  matrix
• Initiate calcification
• Found in periosteum and endosteum
• Osteocytes
• Mature bone cells
• Formed when osteoblasts get trapped in matrix
• Do not secrete matrix
• Maintain bone tissue
• Osteoclasts
• Bone resorption (digest/break down matrix) part
  of normal bone growth, development, maintenance
  and repair
• Found in endosteum

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Bone Matrix

• Organic components (1/3)
• Collagen fibers
• Provide resilience against stretching and
  twisting
• Inorganic components (2/3)
• Mg, F, Na
• Salts that interact to form hydroxyapatite
• Calcium phosphate
• Calcium hydroxide
• Provide hardness and resist compression

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Types of Tissue in Bone

• Connective
• Osseous
• Dense fibrous
• Adipose
• Vascular
• Lymphatic
• Nervous

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Bone Marrow

• Red hematopoietic tissue
• Bone cell forming tissue
• Everywhere in infant
• Yellow fatty tissue
• Young to middle age develop in shafts
• Does NOT produce blood

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I love anatomy!!!!!
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Bone Development

• Osteogenesis (ossification) bone tissue
  formation
• Embryo leads to skeleton
• Intramembranous ossification
• Fibrous membrane replaced with bone
• Endochondral ossification
• Hyaline cartilage replaced with bone
• Most bones develop this way
• More complicated (hyaline cartilage broken down
  first)
• Children leads to bone growth
• Adults leads to bone remodeling and repair

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Intramembranous Ossification

• Osteoblasts permit calcification
• Some osteoblasts trapped in ossification center
  (now considered osteocytes)
• Growth is outward from ossification center
• Osteoblasts require oxygen and nutrients, so
  blood vessels are trapped in bone
• Fibrous membranes?spongy bone?compact bone
• Outer fibrous membrane becomes periosteum

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Endochondrial Ossification

• Chondrocytes in center of shaft increase in size
  and calcify
• Deprived of nutrients and die

• Vessels grow into perichondrium
• Inner layer turns to osteoblasts
• Perichondrium now periosteum
• Thin layer of bone formed around shaft
• Bone collar provides support

• Calcified cartilage breaks down
• Osteoblasts replace with spongy bone
• 1 oss. center- bone dev and spreads toward
  epiphysis

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Endochondrial Ossification

• 1 oss. center enlarges
• Osteoclasts break down spongy bone
• Medullary cavity now open
• Osteoblasts move to epiphysis

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Bone Growth

• Length
• Primary ossification center
• center of diaphysis
• Thickness
• Secondary ossification center
• center of epiphysis

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Hormonal Effects on Bone Growth

• Growth Hormone (GH)
• Produced by pituitary gland
• Stimulates protein synthesis and cell growth
• Thyroxine
• Produced by thyroid gland
• Stimulates cell metabolism and increases
  osteoblast activity
• Sex Hormones at Puberty
• Cause osteoblasts to produce bone faster than
  epiphyseal cartilage can divide
• Growth spurt
• Epipyseal plate closure
• Estrogens (female)
• Cause faster closure of plate than androgens
• Androgens (male)
• Parathyroid Hormone
• Increases blood calcium level (decreases bone
  calcium)
• Inhibits osteoblast Stimulates osteoclast
• Calcitonin
• tones down blood calcium level (increases bone
  calcium)
• Inhibits osteoclast stimulates osteoblast

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Nutrients and Bone Growth

• Calcium and phosphate salts
• Hormone calcitriol and Vit D allow absorption
• Vitamins A, C, K, B12

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Types of Fractures

• Simple - the bone is broken, but the skin is not
  lacerated
• Compound - skin is pierced by the bone or by a
  blow that breaks the skin at the time of the
  fracture
• Greenstick - fracture on one side of the bone,
  causing a bend on the other side of the bone.
• Spiral fracture wraps around bound in spiral
  manner
• Comminuted - results in three or more bone
  fragments.
• Transverse - fracture is at right angles to the
  long axis of the bone
• Compression occurs in vertebrate
• Lisfranc - one or all of the metatarsal bones are
  displaced from the tarsus

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Cervical Fracture
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Compound Transverse Fracture
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Lisfrank Fracture/Dislocation
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Fractures
Bony
(Fracture Hematoma)
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Skeletal Disorders

• Osteomalacia
• soft bones
• Lacking minerals (ie. Calcium, vit D)
• Rickets
• Child form of osteomalacia
• More detrimental since bones are still growing
• Signs bowed legs deformities of pelvis, ribs
  and skull
• Osteomyelitis
• bone marrow inflammation
• Caused by pus-forming bacteria that enter via
  wound or nearby infection
• Osteoporosis
• Bone degradation occurs faster than bone can be
  deposited
• Decrease in bone mass
• Porous bones
• Fractures in the vertebrate and femur are common
• Most common postmenopause rapid decline in
  estrogen (stimulates osteoblasts and inhibits
  osteoclasts

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Skeletal Disorders

• Giantism
• Childhood hypersecretion of GH
• Excessive growth
• Acromegaly
• Adult hypersecretion of GH
• Overgrowth of face, feet, hands
• Pituitary Dwarfism
• Childhood deficiency of GH
• Short long bones max height is 4 ft.
• Pagets Neoplasms
• Bone remodeling process disturbed
• Bones are abnormal, enlarged, not as dense,
  brittle, and prone to fracture
• Affects older adults