1. 7
The Skeleton: Part A

2. The skeleton accounts of 20% of body mass
Introduction
The skeleton accounts of 20% of body mass
There are 206 bones in the human skeleton
Ligaments –band of fibrous tissue that connects bones
Divisions of the Skeleton
Axial Skeleton and Appendicular

3. Contains of 80 bones that collectively form the axis of the body trunk
The Axial Skeleton
Contains of 80 bones that collectively form the axis of the body trunk
Protect the brain and spinal cord and organs within the thoracic cavity
Three major regions of the axial skeleton
Skull
Vertebral column
Thoracic cage
Hyoid

4. Cranium Skull Facial bones Clavicle Thoracic cage Scapula (ribs and
sternum)
Scapula
Sternum
Rib
Humerus
Vertebra
Vertebral
column
Radius
Ulna
Sacrum
Carpals
Phalanges
Metacarpals
Femur
Patella
Tibia
Fibula
Tarsals
Metatarsals
(a) Anterior view
Phalanges
Figure 7.1a

5. General Characteristics
The Skull
General Characteristics
Composed of: cranial and facial bones
Cranial bones enclose and protect the brain
Facial bones form the framework of the face, contain cavities for special sense organs, provide openings for food & air, secure teeth, anchor facial muscles
Most bones of the skull are: paired

6. Bones of cranium (cranial vault)
Coronal
suture
Squamous
suture
Lambdoid
suture
Facial
bones
(a) Cranial and facial divisions of the skull
Figure 7.2a

7. Major Sutures of the Skull
Four sutures mark the articulations of parietal bones with frontal, occipital, and temporal bones:
Coronal (frontal) suture—between parietal bones and frontal bone
Sagittal suture—between right and left parietal bones
Lambdoid suture—between parietal bones and occipital bone
Squamous suture—between parietal and temporal bones on each side of skull

8. Coronal suture Lambdoid suture Squamous suture Frontal bone
Sphenoid bone
(greater wing)
Parietal bone
Temporal bone
Lambdoid
suture
Squamous
suture
Occipital
bone
(a) External anatomy of the right side of the skull
Figure 7.5a

9. Sagittal suture Parietal bone Lambdoid suture Occipital bone
Superior nuchal line
External
occipital
protuberance
Occipital
condyle
(b) Posterior view
Figure 7.4b

10. Calvaria – Cranial vault “skull cap”
The Skull
Calvaria – Cranial vault “skull cap”
Cranial Base (floor) of the skull is divided into three regions:
Anterior cranial fossa-accommodates the frontal lobes of brain
Middle cranial fossa- accomodates the temporal lobes
Posterior cranial fossa-deepest region houses cerebellum

11. (b) Superior view of the cranial fossae
Anterior cranial
fossa
Middle cranial
fossa
Posterior cranial
fossa
(b) Superior view of the cranial fossae
Figure 7.2b

12. Four pair of cavities within the skull bones called: paranasal sinuses
The four pair are:
Sphenoid
Ethmoid
Maxillary
Frontal
Each cavity is lined with mucous membranes that form mucus, which drains into the nasal cavity

13. Frontal sinus Frontal sinus Ethmoidal air cells (sinus) Ethmoidal
Sphenoid
sinus
Sphenoid
sinus
Maxillary
sinus
Maxillary
sinus
(a) Anterior aspect
(b) Medial aspect
Figure 7.15

14. The Orbits
Composed of: Cranial and facial bones; 7 bones in each orbit –frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal, and ethmoid

15. • Lesser wing of sphenoid bone
Superior
orbital fissure
Roof of orbit
Supraorbital notch
Optic canal
• Lesser wing of sphenoid bone
• Orbital plate of frontal bone
Medial wall
• Sphenoid body
Lateral wall of orbit
• Orbital plate of ethmoid bone
• Zygomatic process of frontal bone
• Frontal process of maxilla
• Greater wing of sphenoid bone
• Lacrimal bone
• Orbital surface of zygomatic bone
Nasal bone
Floor of orbit
Inferior orbital fissure
Infraorbital groove
• Orbital process of palatine bone
Zygomatic bone
• Orbital surface of maxillary bone
Infraorbital foramen
• Zygomatic bone
(b) Contribution of each of the seven bones forming the right orbit
Figure 7.13a

16. The Nasal Cavity
The roof, superior/lateral walls and superior portion of the nasal septum are formed by: the ethmoid bone
The floor is formed anteriorly by the palatine processes of the maxillae and the palatine bones
The cavity is divided into right and left halves by the nasal septum

17. (perpendicular plate) Palatine bone (horizontal plate)
Frontal sinus
Superior
nasal concha
Ethmoid
bone
Middle
nasal concha
Inferior nasal
concha
Nasal bone
Sphenoid
bone
Maxillary bone
(palatine process)
Palatine bone
(perpendicular plate)
Palatine bone
(horizontal plate)
Figure 7.14a

18. The Nasal Cavity
Nasal conchae- on the lateral walls: formed by the superior and middle nasal conchae of ethmoid bone
The conchae and septum are lined with a mucus secreting mucosa that moistens & warms air, helps cleanse it of debris
Cribriform plate –porous superior surface of ethmoid for passage of olfactory fibers (smell)

19. Crista galli Olfactory foramina Cribriform plate Perpendicular plate
Middle nasal concha
Figure 7.10

20. General Characteristics
The Vertebral Column
General Characteristics
Contains 33 vertebrae, some of which are fused in adults
Intervertebral discs-
Inner part
Nucleus pulposus- gelatinous nucleus that gives the disc its elasticity and compressibility

21. The Vertebral Column Outer part
Anulus fibrosus- Outer collar composed of collagen and fibrocartilage
Herniated disc – usually involves rupture of the anulus fibrosus followed by protrusion of the spongy nucleus pulposus through the anulus

22. Intervertebral disc Anulus fibrosus Nucleus pulposus
Median section of three vertebrae, illustrating the composition of the discs and the ligaments
Figure 7.17a

23. (c) Superior view of a herniated intervertebral disc
Spinal cord
Herniated portion
of disc
Anulus fibrosus
of disc
Nucleus
pulposus
of disc
(c) Superior view of a herniated intervertebral disc
Figure 7.17c

24. Vertebral Column: Curvatures
Increase the resilience and flexibility of the spine
Four normal curvatures
Two primary curvatures- Thoracic and sacral
Born with primary curvatures
Two secondary curvatures- Cervical and lumbar
Develop after birth

25. Figure 7.37

26. The Appendicular Skeleton
Characteristics
Includes: The upper and lower limbs and their girdles (pectoral and pelvic girdle)

27. Comparison of Male and Female Pelves
The true pelvis is: the region inferior to the pelvic brim containing pelvic organs
The pubic angle is degrees in females and degrees in males
The acetabula are: smaller and farther apart in females and larger and closer together in males

28. Animation: Rotatable pelvis
Base of sacrum
Iliac crest
Sacroiliac
joint
Iliac fossa
Anterior
superior
iliac spine
Sacral
promontory
Coxal
bone
(os coxae
or hip
bone)
Anterior inferior
iliac spine
llium
Sacrum
Pubic
bone
Pelvic brim
Coccyx
Acetabulum
Pubic tubercle
Ischium
Pubic crest
Pubic symphysis
Pubic arch
PLAY
Animation: Rotatable pelvis
Figure 7.29

29. Table 7.4

30. Table 7.4

31. Frontal bone Glabella Parietal bone Frontonasal suture
Supraorbital foramen
(notch)
Squamous part
of frontal bone
Supraorbital margin
Nasal bone
Superior orbital
fissure
Sphenoid bone
(greater wing)
Optic canal
Temporal bone
Inferior orbital
fissure
Ethmoid bone
Lacrimal bone
Middle nasal
concha
Zygomatic bone
Ethmoid
bone
Infraorbital foramen
Perpendicular
plate
Maxilla
Inferior nasal concha
Mandible
Vomer
Mental
foramen
(a) Anterior view
Mandibular symphysis
Figure 7.4a

32. Intermaxillary suture Hard palate Palatine bone (horizontal plate)
(palatine process)
Incisive fossa
Intermaxillary suture
Hard
palate
Palatine bone
(horizontal plate)
Median palatine suture
Infraorbital foramen
Maxilla
Zygomatic bone
Sphenoid bone
(greater wing)
Temporal bone
(zygomatic process)
Foramen ovale
Vomer
Foramen spinosum
Foramen lacerum
Mandibular
fossa
Carotid canal
External acoustic meatus
Styloid process
Stylomastoid
foramen
Mastoid process
Temporal bone
(petrous part)
Jugular foramen
Occipital condyle
Pharyngeal tubercle
of basilar region of
the occipital bone
Inferior nuchal line
Parietal bone
Superior nuchal line
External occipital crest
External occipital
protuberance
Foramen magnum
(a) Inferior view of the skull (mandible removed)
Figure 7.6a