Skeletal Tissue
I. Functions of Skeletal System
A. Support
B. Protection
C. Movement
D. Mineral Storage (Calcium + Phosphorus)
E. Hematopoiesis (blood cell formation in red marrow)
F. Energy Storage (lipids/fat stored in yellow marrow)
Cartilage – take notes from the ppt. Know what are the various types of cartilage and their locations and functions.
n External ear - elastic
n Nose - hyaline
n “Articular” – covering the ends of most bones and movable joints - hyaline
n “Costal” – connecting ribs to sternum - hyaline
n Larynx - voice box –elastic
n Epiglottis – flap keeping food out of lungs - elastic
n Cartilaginous rings holding open the air tubes of the respiratory system (trachea and bronchi) hyaline
n Intervertebral discs - fibrocartilage
n Pubic symphysis - fibrocartilage
n Articular discs such as meniscus in knee joint - fibrocartilage
II. Histology of Skeletal Tissue (Osseous Tissue)
n Functions Support (give body it’s shape)
n Movement: muscles attach by tendons and use bones as levers to move body
n Protection
n Skull – brain
n Vertebrae – spinal cord
n Rib cage – thoracic organs
n Mineral storage
n Calcium and phosphorus
n Released as ions into blood as needed
n Blood cell formation and energy storage
n Bone marrow: red makes blood, yellow stores fat
A. Different Cell Types
1. osteoprogenitor cells give rise to osteoblasts
a. found in periosteum, endosteum, and canals
2. osteoblasts secrete proteins, Ca, P
a. found on bone surface (where growth occurs)
3. osteocytes maintain bone integrity
a. in the bone tissue itself, matrix surrounds
4. osteoclasts degrade and absorb bone during growth
a. derived from white blood cells, on surface
B. Chemical Composition
1. 35% collagenous fibers as in connective tissue
2. 65% mineral salts - calcium phosphate + carbonate
3. hardening depends on correct amount of each
C. Classification of Bones
1. Long Bones – considerably longer than wide; shaft with 2 ends (most limb bones, finger bones, etc.)
2. Short Bones – roughly cube shaped (wrist bones)
i. Sesamoid bone – short bone within a tendon (patella)
3. Flat bones – Flattened, thin, and usually curved (most cranial bones, ribs, sternum, and scapula)
4. Irregular bones – irregularly shaped (vertebrae, hip bones)
III. General Anatomy of a Long Bone (eg. humerus)
A. Diaphysis - main shaft of the bone
B. Epiphysis - large end of the bone
C. Metaphysis - where above meet during bone growth
D. Articular Cartilage - covers epiphysis, reduce friction
E. Periosteum - dense, white covering around the bone
a. fibrous layer - blood, lymph, nerves pass through
b. osteogenic layer - where bone cells originate
F. Medullary (marrow) Cavity - adults, yellow marrow
G. Endosteum - lines medullary cavity, houses bone cells
IV. Microanatomy of Compact (Dense) Bone
A. General Features
1. few empty spaces (dense)
2. thicker in diaphysis than epiphysis
3. concentric ring-like structure
B. Osteon (Haversian System) - Components of Compact Bone
1. central (Haversian) canal - vessels and nerves
2. osteocytes - mature bone cells (from osteoblasts)
3. lacunae - spaces where osteocytes reside
4. lamellae - rings around canal, house lacunae
5. canaliculi - projections from lacunae + osteocytes
C. Supporting Structures
1. perforating (Volkmann) canals - run perpendicular
2. interstitial lamellae - between osteons
V. Microanatomy of Spongy (Cancellous) Bone
A. General Features
1. many spaces filled with red marrow (not yellow)
2. most of epiphysis of long bones in adult
3. found in short, flat, irregular bones
B. Trabecular Lattice Structure
1. trabeculae - irregular, sponge-like network
2. lacunae - spaces within trabeculae for osteocytes
3. spaces - filled with red marrow (hematopoiesis)
VI. Ossification: The Formation of Bone During Development
A. Different Cells Involved
1. mesenchymal cells - migrate to location in embryo
2. chondroblasts - cartilage formation
3. osteoblasts - bone formation
B. Intramembranous Ossification (from fibrous membrane)
1. ossification center - where osteoblasts concentrate
2. osteoblasts secrete collagen fibers for matrix
3. calcification - Ca salts secreted to cement matrix
4. osteoblasts surrounded --> osteocytes
5. trabeculae - result when hardened bone forms
6. spongy bone now in place with red marrow
7. in time, spongy bone reconstructed -> compact bone
C. Endochondral Ossification (replacing hyaline cartilage)
1. cartilage "bone model" formed in the embryo
2. perichondrium - membrane around the cartilage
3. vessel penetrates cartilage, brings osteoblasts
4. cartilage converted into compact bone
5. perichondrium --> periosteum
6. chondrocytes gradually hypertrophy and die
7. vessels move into space and convert to bone
8. primary ossification center - in diaphysis
9. secondary ossification center - in epiphysis
10. epiphyseal plate - between the two, still cartilage
VII. Bone Growth and Remodeling
Factors regulating bone growth
n Vitamin D: increases calcium from gut
n Parathyroid hormone (PTH): increases blood calcium (some of this comes out of bone)
n Calcitonin: decreases blood calcium (opposes PTH)
n Growth hormone & thyroid hormone: modulate bone growth
n Sex hormones: growth spurt at adolescense and closure of epiphyses
A. Four Zones of Epiphyseal Plate - Longitudinal Growth
1. zone of reserve cartilage
a. chondrocytes scattered throughout
b. anchor plate to epiphyseal bone
2. zone of proliferating cartilage
a. chondrocytes stacked together
b. replace dead cells at diaphyseal surface
3. zone of hypertrophic cartilage
a. larger chondrocytes, close to diaphysis
b. chondrocytes form mature cartilage
4. zone of calcified matrix
a. dead chondrocytes, calcified matrix around
b. absorbed by osteoclasts
c. osteoblasts lay down new bone on remains
d. metaphysis - between epiphysis and diaphysis
B. Bone Remodeling - Spongy Bone Converted to Compact Bone
1. osteoclasts - resorption of old bone tissue
a. lysosome release of digestive enzymes
b. cell "phagocytoses" (engulfs) particles
2. osteoblasts - lay down new bone in its place
3. bone constantly undergoes remodeling throughout life
a. Ca needed in muscle, nerve, blood clotting
b. fractures repaired immediately
4. Factors essential for proper bone growth
a. Ca and P in proper amount in diet
b. trace amounts of Boron and Manganese
c. Vitamin D - regulates Ca metabolism
d. Vitamin C - maintenance of bone matrix
e. Vitamin A - osteoclast/blast function
f. Vitamin B12 - osteoblast function
g. Human Growth Hormone (HGH) - pituitary
h. Calcitonin - thyroid, Ca absorption to bone
i. Parathormone - parathyroid, Ca release to blood
j. Sex Hormones - Testosterone + Estrogen
Classification of bones by shape
n Long bones
n Short bones
n Flat bones
n Irregular bones
n Pneumatized bones
n Sesamoid bones
The Bone Markings
You will see that each bone has special features (overviewed in section I below) that provide Sites of Attachment (for muscles, ligaments, tendons, etc.) and Sites of Passage (for blood vessels and nerves).
Study the prefixes and suffixes.. These terms are used repeatedly during the remainder of the course to describe various parts of all of the major systems. STUDY and KNOW these word components. They will be an enormous aid in learning the terms of GROSS Anatomy.
From this point on, there is no substitute for STUDYING. Do not do it all in one sitting. Constant review and quizzing each other is the best way to learn it and know it.
One super way to learn all of the terms you are about to be bombarded with is to make 3'X 5' FLASH CARDS. Write the term on one side and where it is located on the other. These are extremely useful when it comes to quizzing yourself in the lab and certainly in reviewing for quiz/midterm/final. The process of making the cards themselves is very didactic. Use the boldface terms in each of the laboratories. I cannot overemphasize how useful flashcards can be in learning anatomical terminology.
Students often wish they had known of this technique earlier in the term so they had a simple way to review at the end. Start now and you will not be one of those students. Believe me, I have been in that position before. Learn from my mistakes!
I. Different Bone Markings - Essential Terminology (only a partial list!)
* Depressions and Openings
A. fissure cleft-like opening between adjacent parts of bones through which vessels & nerves pass
B. foramen hole through which blood vessels, nerves ligaments can pass
C. meatus tunnel-like passageway through a bone
D. sinus cavity within a bone with narrow opening
E. sulcus groove or depression that accommodates a soft structure such as vessels, nerve, tendon
F. fossa depression in/on a bone; generally at a joint
G. process prominent projection or point of attachment
* Articular Processes (of the joints)
H. condyle large, rounded articular (joint) prominence
I. head rounded articular projection supported by a more constricted portion of a bone (neck)
J. facet smooth, flat surface on a bone
* Processes for Attachment (tendons, ligaments, etc.)
K. tubercle small, rounded process
L. tuberosity large, rounded, usually rough process
M. trochanter large, blunt projection; only on the femur
N. line less prominent ridge than a crest
O. spine sharp, slender process
P. epicondyle prominence found "above" a condyle