1. Chapter 7 Skeletal System
Skeletal System Functions:
Give shape to structures-Ex. Face
Support and protection of tissues:
Ex: Lower limbs, pelvis, and vertebrae support the body’s weight
Ex: Skull protects the eyes, ear, and brain
Blood cell formation
Mineral storage
Ex: Calcium

2. Bone Classification Long Bones (a) Short Bones (b) Flat Bones (c)
Irregular Bones (d)
Sesamoid (Round)
Bones (e)

3. Parts of a Long Bone distal proximal red yellow epiphysis diaphysis
compact bone
spongy bone
articular cartilage
periosteum
endosteum
medullary cavity
trabeculae
marrow
red
yellow

4. 2 Parts of a Long Bone Epiphysis- Proximal- Distal- Diaphysis-
Medularry cavity-
Compact bone-
Spongy bone-
Red bone marrow-
Yellow bone marrow-

5. Compact and Spongy Bone

6. Microscopic Structure of Compact Bone
Osteon-
Central canal-
perforating canal
osteocyte
lacuna
bone matrix

7. Bone Development (osteogenesis or ossification)
1. Intramembranous Ossification
bones originate within sheetlike layers of connective tissues
broad, flat bones
skull bones (except mandible)
intramembranous bones
2. Endochondral Ossification
bones begin as hyaline cartilage
form models for future bones
most bones of the skeleton
endochondral bones

8. Endochondral Ossification (hylaine cartilage model)
A/B. Bones start as cartilage in fetus covered with a layer of bone matrix (periosteum)
C. Bone matrix made by osteoblasts (bone-forming cells)
D/F. As the fetus develops the cartilage model is digested away opening up the medullary cavity
E. By birth most of the cartilage has been converted to bone except articular cartilage (cover ends of bone) and epiphyseal plates (line of cartilage through the epiphysis)
E. As child gets older, bones become longer along the epiphyseal plates

9. Ossification How bones grow longer
New cartilage is formed on the epiphyseal plate facing the bone ends and along the external end of the articular cartilage.
As new cartilage is added the old cartilage is replaced with bony matrix.
This process lengthens the bone.

10. Ossification How bones grow wider
Osteoblasts add bone tissue to the periosteum on the external face of the diaphysis
Osteoclasts (bone destroying cells) remove bone tissue from the endosteum on the internal face of the diaphysis
These processes happen at the same rate which causes the bone to widen.

11. What controls bone growth?
Parathyroid (PTH) Hormone
The parathyroid gland in the neck reads the calcium levels in the blood. When calcium levels are low the parathyroid releases PTH hormone to activate osteoclasts. Osteoclasts “eat away” bone tissue from the human skeleton to release calcium into the bloodstream. This process brings up the calcium levels in the blood. The opposite occurs when calcium levels are too high in the blood.

12. Factors Affecting Bone Development, Growth, and Repair
Deficiency of Vitamin A – retards bone development
Deficiency of Vitamin C – results in fragile bones
Deficiency of Vitamin D – rickets, osteomalacia
Insufficient Growth Hormone – dwarfism
Excessive Growth Hormone – gigantism, acromegaly
Insufficient Thyroid Hormone – delays bone growth
Sex Hormones – promote bone formation; stimulate ossification of epiphyseal plates
Physical Stress – stimulates bone growth

13. Bones of the Skull
Human skull consist of 26 bones 8 bones make up the cranium 14 bones make up the face

14. Cranium forehead roof of nasal cavity roofs of orbits frontal sinuses
supraorbital foramen
coronal suture

15. Cranium side walls of cranium roof of cranium sagittal suture
2. Parietal (2)
side walls of cranium
roof of cranium
sagittal suture

16. Cranium back of skull base of cranium foramen magnum
3. Occipital (1)
back of skull
base of cranium
foramen magnum
occipital condyles

17. Cranium side walls of cranium floor of cranium
4. Temporal (2)
side walls of cranium
floor of cranium
floors and sides of orbits
squamous suture
mandibular fossae
external acoustic meatus
styloid process
zygomatic process
(makes zygomatic arch)

18. Cranium base of cranium sides of skull floors and sides of orbits
5. Sphenoid (1)
base of cranium
sides of skull
floors and sides of orbits
sphenoidal sinuses

19. Cranium 6. Ethmoid (1) roof and walls of nasal cavity floor of cranium
Makes nasal cavity

20. Facial Skeleton upper jaw anterior roof of mouth floors of orbits
1. Maxillary (2)
upper jaw
anterior roof of mouth
floors of orbits
sides of nasal cavity
floors of nasal cavity

21. Facial Skeleton L shaped bones located behind the maxillae
2. Palatine (2)
L shaped bones located behind the maxillae
posterior section of hard palate
floor of nasal cavity
lateral walls of nasal cavity

22. Facial Skeleton prominences of cheeks lateral walls of orbits
3. Zygomatic (2)
prominences of cheeks
lateral walls of orbits
floors of orbits
temporal process
(articulates with zygomatic
process)

23. Facial Skeleton medial walls of orbits
4. Lacrimal (2)
medial walls of orbits
groove from orbit to nasal cavity, providing a pathway for tears.
5. Nasal (2)
bridge of nose

24. Facial Skeleton
6. Vomer (1)
inferior portion of nasal septum

25. Facial Skeleton extend from lateral walls of nasal cavity
7. Inferior Nasal Conchae (2)
extend from lateral walls of nasal cavity
Support mucous membranes within nasal cavity

26. Facial Skeleton lower jaw mandibular condyle coronoid process
8. Mandible (1)
lower jaw
mandibular condyle
coronoid process
mandibular foramen
mental foramen

27. Infantile Skull
Fontanels – fibrous membranes

28. Infant Skull