Axial Skeleton..........................

Human Anatomy & Physiology

1. T h e Axial Sk el e t a l BY Dr.V.S . Neharkar, M.Pharm,Ph.D Dept. of Pharmacology, RMDIPER,Chinchwad,Pune

2. Axial skeleton supports and protects organs of head, neck and trunk Axial skeleton: skull (cranium and facial bones) hyoid bone (anchors tongue and muscles associated with swallowing) vertebral column (vertebrae and disks) bony thorax (ribs and sternum) Appendicular skeleton includes bones of limbs and bones that anchor them to the axial skeleton Appendicular skeleton: pectoral girdle (clavicles and scapulae) upper limbs (arms) pelvic girdle (sacrum, coccyx) lower limbs (legs)

3. Axial Skeleton The axial skeleton is composed of the skull, vertebral column, and thoracic cage . Each of these is essentially a “shaped box” which house and protect the most vital organs of the human body, such as the brain, spinal cord , heart, lungs, and kidneys.

4. Part One The Skull – consists of 29 bones and can be subdivided into five areas:

5. Five Subdivisions of the Skull: Cranium (8) Facial Bones (14) Hyoid Bone(1) Ossicles of the Ear (6) Wormian Bones (?) ( Wormian bones, also known as intrasutural bones or sutural bones, are  extra bone pieces  that can occur within a suture (joint) in the skull)

6. THE CRANIUM BONE Enclose the cranial cavity, which supports and protects the brain as well as act as attachment sites for some head and neck muscles The cranium consists of eight (8) bones and is specifically defined as the rounded, bony case enclosing and protecting the brain . The cranium also functions as an attachment surface for important groups of muscles , and in the formation of the sinuses , which serve as resonance chambers and help to reduce the total weight of the skull .

7. SUMMARY OF THE CRANIAL BONES Bones of the cranium : Total 8 bones- Frontal Bone (1) Parietal bones (2) Occipital bone (1) Temporal bones (2) Sphenoid bone (1) Ethmoid bone (1)

8. The frontal bone is the single bone that forms the forehead The frontal bone also forms the supraorbital margin of the orbit. Near the middle of this margin, is the supraorbital foramen, the opening that provides passage for a sensory nerve to the forehead . 1.Frontal Bone Frontal Bone

9. – “top & sides of the head” 2. Parietal Bones (2) Which form the middle part of skull cap

10. – the “back” of the head 3. Occipital Bone (1) Which forms posterior part of the skull and base of the skull.

11. – the “temples” 4. Temporal Bones (2) Which forms the lateral part i.e. ear region of the skull & part of cranial floor.

12. back of the eye socket, anterior temples & base of cranium Sphenoid Bone (1) The sphenoid bone is a single, complex bone of the central skull. It serves as a “keystone” bone, because it joins with almost every other bone of the skull. The sphenoid forms much of the base of the central skull and also extends laterally to contribute to the sides of the skull

13. Ethmoid bone (1) The ethmoid bone is a single, midline bone that forms the roof and lateral walls of the upper nasal cavity, the upper portion of the nasal septum, and contributes to the medial wall of the orbit

14. S p h en o id E t h m o id

15. HUMAN SKULL, SUPERIOR VIEW

16. The Facial Bones The facial bones consist of 14 bones that compose what is known as the human face. Along with the cranial bones, they help to form the nasal cavity and also provide numerous attachment sites for important muscles that control facial expressions and move the jaw.

17. The Facial Bones 2 zygomatic or cheek bones 2 maxilla 2 nasal bones 2 lacrimal bones 1 vomer 2 palatine bones 2 inferior conchae 1 mandible

18. Nasal Bones Form the bridge of the nose Maxillae Form the upper jawbone Form most of the hard palate Separates the nasal cavity from the oral cavity Zygomatic Bones commonly called cheekbones, form the prominences of the cheeks Lacrimal Bones Form a part of the medial wall of each orbit Palatine Bones Form the posterior portion of the hard palate Inferior Nasal Conchae Form a part of the inferior lateral wall of the nasal cavity The Facial Bones

19. Vomer Forms the inferior portion of the nasal septum Mandible Lower jawbone The largest, strongest facial bone The only movable skull bone Nasal Septum Divides the interior of the nasal cavity into right and left sides “Broken nose,” in most cases, refers to septal damage rather than the nasal bones themselves Orbits Eye socket Foramina Openings for blood vessels , nerves , or ligaments of the skull The Facial Bones

20. Nasal bones (2) – “bridge of the nose” These are two small flat bones which form the greater part of the lateral and superior surfaces of the bridge of the nose. They also support the cartilages that form the lateral walls of the nose

21. Maxillary bones or Maxillae (2) upper jaw roof of mouth This originates as two bones but fusion takes place before birth. The maxilla forms the upper jaw, the anterior part of the roof of the mouth, the lateral walls of the nasal cavity and part of the floor of the orbital cavities. The curved, inferior margin of the maxillary bone that forms the upper jaw and contains the upper teeth is the alveolar process of the maxilla

22. Zygomatic bones (2) – “cheek bones” The zygomatic bone is also known as the cheekbone. Each of the paired zygomatic bones forms much of the lateral wall of the orbit and the lateral-inferior margins of the anterior orbital opening The short temporal process of the zygomatic bone projects posteriorly, where it forms the anterior portion of the zygomatic arch

23. Mandible (1) – “jaw bone” or “lower jaw” The mandible forms the lower jaw and is the only moveable bone of the skull. At the time of birth, the mandible consists of paired right and left bones, but these fuse together during the first year to form the single U-shaped mandible of the adultskull . Each side of the mandible consists of a horizontal body and posteriorly, a vertically oriented ramus of the mandible.

24. Lacrimal bones (2) – medial part of the eye socket Each lacrimal bone is a small, rectangular bone that forms the anterior, medial wall of the orbit. The anterior portion of the lacrimal bone forms a shallow depression called the lacrimal fossa , and extending inferiorly from this is the nasolacrimal canal .

25. Palatine bones (2) – posterior portion of the roof of mouth & base of the eye socket roof of mouth & base of the eye socket These are two L-shaped bones. The horizontal parts unite to form the posterior part of the hard palate and the perpendicular parts project upwards to form part of the lateral walls of the nasal cavity. At their upper extremities they form part of the orbital cavities.

26. Inferior nasal conchae (2) – nasal cavity “baffles ” Each concha is a scroll-shaped bone which forms part of the lateral wall of the nasal cavity and projects into it below the middle concha. The superior and middle conchae are parts of the ethmoid bone. These are bony plates that curve downward as they project into the space of the nasal cavity. They serve to swirl the incoming air , which helps to warm and moisturize it before the air moves into the delicate air sacs of the lungs. This also allows mucus, secreted by the tissue lining the nasal cavity, to trap incoming dust, pollen, bacteria, and viruses.

27. Vomer bone (1) The unpaired vomer bone, often referred to simply as the vomer , is triangular-shaped thin flat bone which extends upwards from the middle of the hard palate to form the main part of the nasal septum. Superiorly it articulates with the perpendicular plate of the ethmoid bone.

28. Nasal Zygomatic Maxilla Mandible L ac r i ma l P a lati n e Inferior Nasal Conchae V o me r Bones of the face :

29. The Hyoid Bone The hyoid bone is an independent bone that does not contact any other bone and thus is not part of the skull. It is a small U-shaped bone located in the upper neck near the level of the inferior mandible , with the tips of the “ U”pointing posteriorly . The hyoid serves as the base for the tongue above, and is attached to the larynx below and the pharynx posteriorly . Movements of the hyoid are coordinated with movements of the tongue, larynx , and pharynx during swallowing and speaking.

30. The Vertebral Column The vertebral column is also known as the spinal column or spine . It consists of a sequence of vertebrae (singular = vertebra), each of which is separated and united by an intervertebral disc . Together, the vertebrae and intervertebral discs form the vertebral column . It is a flexible column that supports the head, neck , and body and allows for their movements . It also protects the spinal cord, which passes down the back through openings in the vertebrae.

31. The vertebral column consists of 24 separate movable, irregular bones 7 cervial vertebrae 12 thoracic movable 5 lumbar 1 sacrum (5 fused 1 coccyx (4 fused) The Vertebral Column immovable

32. General Structure of Vertebrae 1. Cervical vertebrae (C1-C7) Formed framework of neck region Support skull Small in size Presense foramen in each transverse process 2. Thoracic vertebrae (T1-T12) Formed posterior part of thoracic cage Articulates with associated ribs

33. 3 . Lumbar Vertebrae (L1-L5) 34 Formed skeletal support for posterior abdominal wall Characterized by large in size 4. Sacrum Vertebrae Fusion of 5 sacra l bones Immovable (synostosis) Articulates with L5 at lumbosacral joint Articulates laterally with pelvic bone at sacroiliac joint. Formed posterior wall of lower abdominal and pelvic cavity 5. Coccyx Fusion of 4 coccyx bones Immovable (synostosis) Formed part of pelvic cavity

34. Structure of a Typical Vertebrae Within the different regions of the vertebral column, vertebrae vary in size and shape, but they all follow a similar structural pattern. A typical vertebra will consist of a- body vertebral arch seven processes two transverse processes One spinous process four articular processes Typical Vertebrae

35. Largest thick part of vertebra. D isc -shaped anterior portion Weight bearing portion – size increases inferiorly Its inferior and superior surfaces are roughened and give attachment to the intervertebral disc . Anterior and lateral surfaces contain nutrient foramina – pathway for blood vessels . 36 BODY OF VERTEBRAE

36. Extend backwards from the body of the vertebra. ▶ Consists of a pair of pedicles and a pair of laminae. ▶ The pedicle project backward from the body to unite with the laminae. 37 VERTEBRAL ARCH

37. Pedicle: ▶ two short, thick processes, which project backward. ▶ the concavities above and below the pedicles are named the vertebral notche Laminae: ▶ two broad & flat plates directed backward and medialward from the pedicles. ▶ the laminae end in a single sharp, slender projection called a spinous process. VERTEBRAL ARCH

38. 2 9 seven processes arise from the vertebral arch two transverse processes One spinous process four articular processes PROCESS OF THE VERTEBRAE

39. TRANSVERSE PROCESS: ▶ Extends posterolaterally for the junction between pedicle and laminae on each side (left and right) ONE SPINOUS PROCESS: ▶ A single spinous process projects posteriorly from the junction of the laminae. ▶ These 3 processes serve as points of attachment for muscles. PROCESS OF THE VERTEBRAE

40. ARTICULAR PROCESSES ( Zygapophyses ): ▶ At the junction between pedicles and lamina meet, also projecting superior and inferior articular process. ▶ At the end of these processes – concave surface (facet) 41

41. Between the bodies of the adjacent vertebrae C2 to the sacrum . Each disc forms a cartilaginous joint to allow slight movement of the vertebrae, and acts as a ligament to hold the vertebrae together. 42 INTERVERTEBRAL DISCS

42. Each vertebral discs consist of: ▶ a n o ut e r f i b r ou s ring co n s i s tin g o f fibrocartilage called annulus fibrosus (annalus = ringlike). ▶ I n ne r so f t , pu l p y, h i gh l y e l as ti c subs t anc e called the nucleus pulposus (pulposus = pulplike), which is acts as a shock absorber , absorbing the impact of the body's daily activities and keeping the two vertebrae separated 43

43. Nucleus pulposus hardens and less elastic with age. Narrowing of discs and c o m p r e ss i o n o f t h e ve r t eb r a e results in a decrease in the height with age . A tear can occur within the annulus fibrosus (ring) and cause the nucleus pulposus may track into the vertebral canal or intervertebral foramen to impinge on neural structures 44

44. Binds the vertebrae and forms a strong joint Permits various movements of the vertebral column Absorbs vertical shock and avoid friction during intervertebral joints movements. 45

45. ▶ Vertebral foramen contains : spinal cord and its roots, spinal meninges, ASA and PSA, Venous Plexus ▶ The vertebral foramina of all vertebrae form the vertebral (spinal) canal.

46. 47 Cervical Vertebrae Typical cervical vertebrae, such as C4 or C5, have several characteristic features that differentiate them from thoracic or lumbar vertebrae. Cervical vertebrae have a small body, reflecting the fact that they carry the least amount of body weight. Cervical vertebrae usually have a bifid (Y-shaped) spinous process. The spinous processes of the C3–C6 vertebrae are short, but the spine of C7 is much longer. The superior and inferior articular processes of the cervical vertebrae are flattened and largely face upward or downward , respectively.

47. 48 Cervical Vertebrae- Atlas The first and second cervical vertebrae are further modified, giving each a distinctive appearance. The first cervical (C1) vertebra is also called the atlas , because this is the vertebra that supports the skull on top of the vertebral column . The C1 vertebra does not have a body or spinous process . Instead, it is ring-shaped, consisting of an anterior arch and a posterior arch . The transverse processes of the atlas are longer and extend more laterally than do the transverse processes of any other cervical vertebrae. The superior articular processes face upward and are deeply curved for articulation with the occipital condyles on the base of the skull. The inferior articular processes are flat and face downward to join with the superior articular processes of the C2 vertebra.

48. 49 Cervical Vertebrae- Axis The second cervical (C2) vertebra is called the axis, because it serves as the axis for rotation when turning the head toward the right or left. The axis resembles typical cervical vertebrae in most respects, but is easily distinguished by the dens (odontoid process), a bony projection that extends upward from the vertebral body. The dens joins with the inner aspect of the anterior arch of the atlas, where it is held in place by transverse ligament.

49. 50 Thoracic Vertebrae The bodies of the thoracic vertebrae are larger than those of cervical vertebrae. The characteristic feature for a typical mid-thoracic vertebra is the spinous process , which is long and has a pronounced downward angle that causes it to overlap the next inferior vertebra. The superior articular processes of thoracic vertebrae face anteriorly and the inferior processes face posteriorly. These orientations are important determinants for the type and range of movements available to the thoracic region of the vertebral column. Thoracic vertebrae have several additional articulation sites, each of which is called a facet, where a rib is attached.

50. 51 Lumbar Vertebrae Lumbar vertebrae carry the greatest amount of body weight and are thus characterized by the large size and thickness of the vertebral body. They have short transverse processes and a short, blunt spinous process that projects posteriorly. The articular processes are large, with the superior process facing backward and the inferior facing forward.

51. 52 Sacrum and coccyx The sacrum is a triangular-shaped bone that is thick and wide across its superior base where it is weight bearing and then tapers down to an inferior, non-weight bearing apex. It is formed by the fusion of five sacral vertebrae, a process that does not begin until after the age of 20. The anterior and posterior surfaces of the sacrum have a series of paired openings called sacral foramina that connect to the sacral canal through spinal nerves to exit The coccyx, or tailbone , is derived from the fusion of four very small coccygeal vertebrae . It articulates with the inferior tip of the sacrum. It is not weight bearing in the standing position, but may receive some body weight when sitting .

52. Bony Thorax Forms the framework of the chest Components of the bony thorax Thoracic vertebrae – posteriorly Ribs – laterally Sternum and costal cartilage – anteriorly Protects thoracic organs Supports shoulder girdle and upper limbs Provides attachment sites for muscles

53. The Bony Thorax

54. The Bony Thorax

55. Sternum This flat bone can be felt just under the skin in the middle of the front of the chest. Formed from three sections Manubrium – superior section Articulates with medial end of clavicles at the sternodavicular joints and with the first two pairs of ribs. Body – bulk of sternum Sides are notched at articulations for costal cartilage of ribs 2–7 Xiphoid process – inferior end of sternum. It gives attachment to the diaphragm, muscles of the anterior abdominal wall.

56. Sternum Anatomical landmarks Jugular notch Central indentation at superior border of the manubrium Sternal angle A horizontal ridge where the manubrium joins the body

57. RIBS There are 12 pairs of ribs which form the bony lateral walls of the thoracic cage and articulate posteriorly with the thoracic vertebrae. The first 10 pairs are attached anteriorly to the sternum by costal cartilages, some directly and some indirectly All ribs attach to vertebral column posteriorly True ribs - superior seven pairs of ribs Attach to sternum by costal cartilage False ribs – inferior five pairs of ribs Ribs 11–12 are known as floating ribs- have no anterior attachment.

58. A typical rib

59. The head articulates posteriorly with the bodies of two adjacent thoracic vertebrae and on the tubercle there is a facet that articulates with the transverse process of one . The sternal end is attached to the sternum by a costal cartilage, i.e. a band of hyaline cartilage. The superior border is rounded and smooth while the inferior border has a marked groove occupied by the intercostal blood vessels and nerves. The first rib does not move during respiration. The spaces between the ribs are occupied by the intercostal muscles . During inspiration, when these muscles contract the ribs and sternum are lifted upwards and outwards , increasing the capacity of the thoracic cavity CHARACTERISTICS OF A RIB