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The skeletal system
1. SUPPORT
• Attachment for tendon, framework for body
2. PROTECTION
• Ex: cranial bones protect brain
3. ASSISTANCE IN MOVEMENT
• Work with muscles
4. MINERAL HOMEOSTASIS
• calcium
5. BLOOD CELL FORMATION
• in red bone marrow of select bones
6. TRIGLYCERIDE STORAGE
• Potential energy reserve in adipose cells of yellow bone
marrow
• 1. diaphysis: shaft
• 2. epiphyses: ends
• 3. metaphysis:
between diaphysis
and epiphysis.
Contains hyaline
cartilage in growing
bone.
4. Articular cartilage:
covers ends of
bone to reduce
friction
• 5. periosteum:
surrounds bone;
– serves as an
attachment point
for ligaments and
tendons
6. marrow cavity:
inside diaphysis that
contains fatty
yellow bone marrow
Compact bone tissue
• Strong/light
• Makes up most
of diaphysis
(shaft)
Parts of compact bone
OSTEON: repeating
unit of compact bone
1. Perforating canals:
transverse, for blood
vessels and nerves
2. Central canals: runs
longitudinally
through middle of
osteon; for blood
vessels and nerves
3. Concentric lamellae: rings
around central canals
4. Lacunae: spaces between
lamellae
5. Canaliculi: fluid-filled;
radiating from lacunae in all
directions.
Spongy bone tissue
• Located on ends of long bones and
irregularly shaped bones
• Looks spongy; is not soft
• Sometimes contains red bone marrow
Calcium in bone
• Bones, neurons, muscle cells, blood
clotting, depend on Ca+2 in blood.
• Too high – heart stops
• Too low – osteoporosis, breathing
stops
Calcium homeostasis
• Stimulus: low blood calcium levels
• Receptors: cells of parathyroid gland
• Control center: nucleus of parathyroid cells
(parathryoid hormone – PTH)
• Effectors: osteoclasts activated – releases
calcium from bone
A negative feedback system
• Stimulus: high blood calcium levels
• Receptors: Cells in thyroid gland
• Control center: nucleus of thyroid cells
(secrete calcitonin - hormone).
• Effectors: osteoclasts inhibited: bone
absorbs calcium
What type of feedback system?
SUMMARY
• Thyroid controls high blood calcium
• Parathyroid controls low blood calcium
Axial/Appendicular
divisions of the nervous system