Essentials of Human Anatomy The Skeletal System 2 The Axial Skeletal System

1. Essentials of Human AnatomyThe Skeletal System 2The 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