The document provides a detailed overview of the human axial skeleton, which includes the skull, vertebral column, and bony thorax. It describes the composition and functions of these structures, highlighting the different types of bones within the skull and their roles in protecting vital organs. Additionally, it outlines the vertebral column's structure, consisting of various regions, each with specific characteristics and functions.

1. The Axial
Skel etal
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.

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

6. 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)

7. 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.

8. 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)

9. 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

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

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

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

13. 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

14. 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

15. Sphenoid
Ethmoid

16. HUMAN SKULL, SUPERIOR VIEW

17. 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.

18. 2 zygomatic or cheek bones
2 maxilla
2 nasal bones
2 lacrimal bones
1 vomer
2 palatine bones
2 inferior conchae
1 mandible

19. • 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

20. • 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

21.  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

22. 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

23. 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

24. 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.

25. 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.

26. 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.

27. 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.

28. 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.

29. • Nasal
• Zygomatic
• Maxilla
• Mandible
• Lacrimal
• Palatine
• Inferior Nasal
Conchae
• Vomer
Bones of the face:

30. 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.

31. 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.

32. 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

33. 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

34. 3. Lumbar Vertebrae (L1-L5)
 Formed skeletal support for posterior
abdominal wall Characterized by large in size
4. Sacrum Vertebrae
 Fusion of 5 sacral 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

35. 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

36. • Largest thick part of vertebra.
• Disc-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

37.  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

38. 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

39. 29
 seven processes arise from
the vertebral arch
two transverse processes
 One spinous process
 four articular processes
PROCESS OF THE VERTEBRAE

40. 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

41. 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

42.  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

43. Each vertebral discs consist of:
▶ an outer fibrous ring consisting of
fibrocartilage called annulus fibrosus
(annalus = ringlike).
▶ Inner soft, pulpy, highly elastic substance
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

44.  Nucleus pulposus hardens and
less elastic with age.
 Narrowing of discs and
compression of the vertebrae
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

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

46. ▶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.

47. 47
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.

48. 48
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.

49. 49
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.

50. 50
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.

51. 51
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.

52. 52
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.

53. 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

54. The Bony Thorax

55. The Bony Thorax

56. 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.

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

58. 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.

60. A typical rib

61. 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