1. Ass. Prof. Faculty of Medicine
Essentials of Human Anatomy The Skeletal System 2 The Axial Skeletal System
Chapter 5
Dr Fadel Naim
Ass. Prof. Faculty of Medicine
IUG 1

2. Skeletal Organization
Axial Skeleton
head
neck
trunk
Appendicular Skeleton
upper limbs
lower limbs
pectoral girdle
pelvic girdle

4. The Skull
Cranial bones form the rounded cranium, which completely surrounds and encloses the brain.
Facial bones form the bones of the face. They also
protect the entrances to the digestive and respiratory systems as well as
provide attachment sites for facial muscles

5. Cranium
Frontal (1)

6. Cranium
Parietal (2)

7. Cranium
Occipital (1)

8. Cranium
Temporal (2)

9. Cavities of The Skull
The largest cavity is the cranial cavity, which encloses, cushions, and supports the brain.
The skull also has several smaller cavities, including the orbits (eye sockets), the oral cavity (mouth), the nasal cavity, and the paranasal sinuses.

10. Cranium
Sphenoid (1)

11. Cranium
Ethmoid (1)

12. Facial Skeleton
Maxillary (2)

13. Facial Skeleton
Palatine (2)

14. Facial Skeleton
Zygomatic (2)

15. Facial Skeleton
Lacrimal (2)
Nasal (2)

16. Facial Skeleton
Vomer (1)

17. Facial Skeleton
Inferior Nasal Conchae (2)

18. Facial Skeleton
Mandible (1)

19. Sinuses
Have a mucous lining that helps to humidify and warm inhaled air.
Cause these skull bones to be lighter.
Provide resonance to the voice.

21. Hyoid Bone

22. Fontanels
The regions between the cranial bones are thickened, fibrous membrane remnants that are not yet ossified.
Sometimes referred to as the “soft spots” on a baby’s head.
They close by 15 months of age.
When a baby travels through the birth canal, the cranial bones overlap at these fontanels, in order to ease the baby’s passage.
Newborns frequently have a “cone-shaped” head due to this temporary deformation.
Fontanels – fibrous membranes

24. Sutures of the Skull
Sutures are immovable fibrous joints that form the boundaries between the cranial bones.
Dense regular connective tissue seals cranial bones firmly together at a suture.
Allow the cranium to grow and expand during childhood.
In adulthood, when cranial growth has stopped, the sutures fuse and are obliterated.

27. Functions Of Vertebral Column
1) Support weight
Transmits weight to pelvis and lower limbs
2) Houses and protects spinal cord
spinal nerves leave cord between vertebrae
3) Permits movements
4) Provides for muscle attachments
muscles of back
muscles of head
Neck
upper extremity
thorax

28. Regions and Normal Curvatures
Formed from 33 bones in the adult
Divided into five major regions
Cervical vertebrae
7 vertebrae of the neck region
Thoracic vertebrae
12 vertebrae of the thoracic region
Lumbar vertebrae
5 vertebrae of the lower back
Sacrum
Inferior to lumbar vertebrae
Articulates with coxal bones
Coccyx
Most inferior region of the vertebral column

29. Regions and Normal Curvatures
Four distinct curvatures give vertebral column an S-shape
Cervical and lumbar curvature
concave posteriorly
Thoracic and sacral curvatures
convex posteriorly
Curvatures increase the resilience of the spine

30. General Structure of Vertebrae

32. Cervical Vertebrae Atlas – 1st; supports head
Axis – 2nd; dens pivots to turn head
transverse foramina
bifid spinous processes
vertebral prominens – useful landmark

33. Thoracic Vertebrae
long spinous processes
rib facets

34. Lumbar Vertebrae
large bodies
thick, short spinous processes

35. Sacrum five fused vertebrae median sacral crest
posterior sacral foramina
posterior wall of pelvic cavity
sacral promontory

36. Coccyx
tailbone
four fused vertebrae

37. The Axial Skeleton Throughout Life
Curvatures of the vertebral column
Primary curvatures
thoracic and sacral curvatures
An infant's spine is C-shaped at birth
Secondary curvatures
cervical and lumbar curvatures
Develop when a baby begins to walk
Redistributes weight of the upper body over the lower limbs

38. Three Main Spinal Curvature Deformities
Kyphosis is an exaggerated thoracic curvature that is directed posteriorly, producing a “hunchback” look.
Lordosis is an exaggerated lumbar curvature, often called “swayback,” that is observed as a protrusion of the abdomen and buttocks.
Scoliosis is an abnormal lateral curvature that sometimes results during development when both the vertebral arch and body fail to form, or form incompletely, on one side of a vertebra.
scoliosis is the most common spinal curvature deformity.

41. Thoracic Cage
Consists of the thoracic vertebrae posteriorly, the ribs laterally, and the sternum anteriorly.
Acts as a protective cage around vital organs, such as the heart, lungs, trachea, and esophagus.
Provides attachment points for many muscles supporting the pectoral girdles, the chest, the neck, the shoulders, the back, and the muscles involved in respiration.

43. Ribs Both males and females 12 pairs
Ribs 1–7 are called true ribs. At the anterior body wall, the true ribs connect individually to the sternum by separate cartilaginous extensions called costal cartilages.
Ribs 8–12 are called false ribs because their costal cartilages do not attach directly to the sternum. The costal cartilages of ribs 8–10 fuse to the costal cartilage of rib 7 and thus indirectly articulate with the sternum.
The last two pairs of false ribs (ribs 11 and 12) are called floating ribs because they have no connection with the sternum.

44. THE END