the skeletal system. functions support structural support framework for attachment storage ...
TRANSCRIPT
The Skeletal System
Functions
Support Structural support Framework for attachment
Storage Calcium reserve Energy reserves (Lipids in yellow marrow)
Blood Cell Production Rbc and wbc produced in red marrow
Protection Surrounds soft tissues and organs
Leverage Change magnitude and direction of forces generated by skeletal
muscles
Macroscopic Features of Bone Structure Long Bones
Longer than they are wide Ex. Humerus, femur
Short Bones Roughly equal length and
width Ex. Carpals, tarsals
Flat Bones Thin and broad Ex. Ribs, scapulae, parietal
bones of skull Irregular Bones
Complex shapes
Features of Long Bones
Diaphysis Central shaft
Bone marrow Loose connective tissue
Epiphysis Epanded ends covered w/ articular
cartilage Compact bone
Dense/solid Found in diaphysis
Spongy (cancellous) bone Network of bony rods w/ spaces Found in epiphysis
Periosteum Covers outer surface of bone
Endosteum Lines marrow cavity
Microscopic Features of Bone Histology (central canal, osteocytes,
lacunae, canaliculi) Compact Bone
Haversian system (aka osteons) – arranged in circles
Spongy Bone Trabecule (rods create network)
Cytology Osteocytes – mature bone cells Osteoclasts – giant multinucleated
cells that secrete acids and enzymes to dissolve bony matrix and release Ca (osteolysis)
Osteoblasts – produce new bone (osteogenesis) and promotes Ca deposits in bone matrix
Compact Bone vs. Spongy Bone(Ground bone) (Cancellous bone)
Note the absence of osteons in spongy bone
Bone Formation and Growth Ossification
– replacing other tissues with bone - Intramembranous – (flat) bone develops within
membranes of connective tissue- Endochondrial – (long) bone replaces cartilage- http://commons.bcit.ca/biology/os
sification/files/ossification1.html Calcification
– deposition of calcium salts Body Proportions
Begins at 6 weeks (cartilage skeleton in utero) continues to age 18/25
Requirements Prenatal – minerals absorbed from mother (often
loses bone mass) Consume Ca and P from diet Vitamin D3 allows absorption of Ca and P Vitamin A and C needed for osteoblast activity
Bone Remodeling
Remodeling Removal and replacement of protein and minerals
from bone Heavily stressed bones become thicker and
stronger Inactivity (even brief) causes atrophy
(degeneration)
Homeostasis and Mineral Storage 99% Ca deposited in skeleton Ca+ ions play an important role in both
neurological and muscular processes Ca ion conc. are closely regulated Parathyroid hormone (PTH) and calcitrol
work together to elevate Ca levels in body fluids (bones become weaker)
Calcitonin depresses Ca levels in body fluids (bones become stronger)
Injury and Repair http://video.google.com/videoplay?docid=-6243626
796969590657&q=osteoblasts&total=10&start=0&num=10&so=0&type=search&plindex=1
Fracture – any crack or break in a bone
Healing can take from 4 months to over a year!
Fracture hemotoma – large blood clot closes injured bv
External and internal calluses – thickenings resulting from mitotic divisions
http://commons.bcit.ca/biology/ossification/files/patho.html
Types of Fractures
Aging and Skeletal System
Reduction in bone mass occurs between ages 30 -40
Women lose ~8% skeletal mass per decade Men lose ~3% per decade Epiphyses, vertebrae, and jaws most vulnerable Osteoperosis – decrease in estrogen increases
osteoclast activity (so does smoking); other causes include lack of Ca+ in diet, inactive lifestyle, and certain medications
Bone Markings
Bone Markings