This document provides information about the skeletal system, specifically focusing on the axial skeleton. It defines the main types of bones and classifies them as long, short, flat, irregular, or sesamoid. It then describes the functions of bones and divides the skeletal system into the axial and appendicular skeleton. The majority of the document describes the bones that make up the axial skeleton, including the skull, vertebral column, ribs, and sternum. It provides details on the individual bones of the skull and vertebral column, including their features and locations.

1. Human Anatomy & Physiology-I
Skeletal System- Axial
Presented By: Lovekesh Singh
Assistant Professor
ISF College Of Pharmacy, Moga

2. Contents
• Introduction
• Types of bones
• Functions of bones
• Classification of skeletal system
• Axial Skeletal System and its different types

3. Introduction
Bone- Bone is a strong and
durable type of connective
tissue. It consists of:
• water (25%)
• organic constituents
including osteoid (the
carboncontaining part of
the matrix) and bone cells
(25%)
• inorganic constituents,
mainly calcium phosphate
(50%).

4. Types of bones
Bones are classified as long, short, irregular, flat and sesamoid.
Long bones As the name suggests the length is much greater
than the width and slightly curved for strength. If bones were
straight, the weight of the body would be unevenly distributed,
and the bone would fracture more easily Examples include the
femur, tibia and fibula.
Short bones are somewhat cube-shaped and are nearly equal in
length and width. They consist of spongy bone tissue.
Examples of short bones are the carpal (wrist) bones and the
tarsal (ankle) bones (except for the calcaneus or heel bone,
which is an irregular bone).

5. • Flat bones are generally thin and composed of two nearly
parallel plates of compact bone tissue enclosing a layer of
spongy bone tissue. Flat bones include the cranial bones,
which protect the brain; the sternum (breastbone) and ribs,
which protect organs in the thorax; and the scapulae
(shoulder blades).
• Irregular bones have complex shapes. They vary in the
amount of spongy and compact bone present. Such bones
include the vertebrae (backbones), hip bones, certain facial
bones, and the calcaneus.
• Sesamoid bones (like a sesame seed) develop in certain
tendons where there is considerable friction, tension, and
physical stress, such as the palms and soles. They may vary in
number from person to person. Example; patella (knee cap).

7. Functions of bones
Bones have a variety of functions. They-
• provide the framework of the body
• give attachment to muscles and tendons
• permit movement of the body as a whole and of parts of the
body, by forming joints that are moved by muscles
• form the boundaries of the cranial, thoracic and pelvic
cavities, protecting the organs they contain
• contain red bone marrow in which blood cells develop:
haematopoiesis.
• provide a reservoir of minerals, especially calcium phosphate.

8. Classification
The bones of the skeleton are divided into two groups:
1. The axial skeleton – This part consists of the
• Skull
• Vertebral column
• Ribs
• Sternum.
2. The appendicular skeleton
• Pectoral (shoulder) girdles
• Upper limbs
• Pelvic (hip) girdle
• Lower limbs

9. Axial bones Appendicular bones
Skull
Cranium 8
Face 14
Hyoid 1
Auditory
Ossicles 6
Vertebral
column 26
Thorax
Sternum 1
Ribs 24
Subtotal = 80
Pectoral (shoulder)
girdles
Clavicle 2
Scapula 2
Upper limbs
Humerus 2
Ulna 2
Radius 2
Carpals 16
Metacarpals 10
Phalanges 28
Pelvic (hip) girdle
Hip, pelvic, or coxal bone 2
Lower limbs
Femur 2
Patella 2
Fibula 2
Tibia 2
Tarsals 14
Metatarsals 10
Phalanges 28
Subtotal = 126
Total in an adult
skeleton = 206

12. Skull
The skull rests on the upper end of the vertebral column and its
bony structure is divided into two parts: the cranium and the face.
Cranium The cranium is formed by a number of flat and irregular
bones that provide a bony protection for the brain. It has a base
upon which the brain rests and a vault that surrounds and covers
it. In the mature skull the joints (sutures) between the bones are
immovable (fibrous). The bones have numerous perforations (e.g.
foramina, fissures) through which nerves, blood and lymph vessels
pass. The bones of the cranium are:
1 frontal bone 1 ethmoid bone
2 parietal bones 1 sphenoid bone
2 temporal bones
1 occipital bone
• .

14. Conti….
Frontal bone
• The frontal bone forms the forehead (the anterior part of the
cranium), the roofs of the orbits (eye sockets), and most of the
anterior part of the cranial floor.
• Soon after birth, the left and right sides of the frontal bone are
united by the metopic suture, which usually disappears between the
ages of six and eight.
• The coronal suture joins the frontal and parietal bones and other
fibrous joints are formed with the sphenoid, zygomatic, lacrimal,
nasal and ethmoid bones.

15. Conti….
Parietal bones
• These bones form the sides and roof of the skull. They articulate with
each other at the sagittal suture, with the frontal bone at the coronal
suture, with the occipital bone at the lambdoidal suture and with the
temporal bones at the squamous sutures.
• The inner surface is concave and is grooved by the brain and blood
vessels.
Temporal bones
The two temporal bones forms the inferior parts of cranial cavity.
These bones lie one on each side of the head and form immovable
joints with the parietal, occipital, sphenoid and zygomatic bones. It
consist of following parts
Temporal squama – It is flat part which have zygomatic process
which for connection with zygomatic bone .

16. Conti….
• Petrous part – It forms base of the skull and also forms of bone of
internal ear .
• Mastoid process – It contai mastoid process , A thick region
behind ear .
• Temporamandebular joint – The part where temporal bone joints
with mendible bone .
• External acousticmeatus – Imegiately behind temporamandibular
joint is enternal acoustic meatus which passes inward to the
petrous part .
• Styloid process – It project form lower process of temporal bone
.
• Zygomatic process – The bridge present between the temporal
and zygomatic bone .

17. Occipital bone
• This bone forms the back of the head and part of the base of the
skull. It has immovable joints with the parietal, temporal and
sphenoid bones.
• Formen magnum – The forman magnum is in the inferior part of
the bone, with in their forman medulla olongata connected with the
spinal cord .
• Occipital condyls – The occipital condyles are oval with convex
surface.
Sphenoid bone
• It lies at the middle part of the base of the skull. it articulates with
the occipital, temporal, parietal and frontal bones. This bone is a link
between cranial and facial bones.
• On the superior surface in the middle of the bone there is a little
saddle-shaped depression, the hypophyseal fossa in which the
pituitary gland rests.

18. Conti….
Ethmoid Bone
• It is situated at the roof of nose and between orbits. On each
side are two projections into the nasal cavity, the upper and
middle conchae.
• It is a very delicate bone containing many air sinuses lined with
ciliated epithelium and with openings into the nasal cavity.
• The horizontal flattened part, the cribriform plate, forms the
roof of the nasal cavity and has numerous small foramina
through which nerve fibres of the olfactory nerve (sense of
smell) pass upwards from the nasal cavity to the brain.
• There is also a very fine perpendicular plate of bone that forms
the upper part of the nasal septum.

19. Face
The skeleton of the face is formed by 13 bones in addition to
the frontal bone. It includes
• 2 zygomatic or cheek bones
• 1 maxilla (originated as 2)
• 2 nasal bones
• 2 lacrimal bones
• 1 vomer
• 2 palatine bones
• 2 inferior conchae
• 1 mandible (originated as 2).

21. Conti….
Zygomatic or cheek bones The zygomatic bones form the
prominences of the cheeks and part of the floor and lateral walls of
the orbital cavities.
Maxilla or upper jaw bone 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.
Nasal bones These are two small flat bones which form the greater
part of the lateral and superior surfaces of the bridge of the nose.
Lacrimal bones These two small bones are posterior and lateral to the
nasal bones and form part of the medial walls of the orbital cavities.
Each is pierced by a foramen for the passage of the nasolacrimal
duct which carries the tears from the medial canthus of the eye to
the nasal cavity.

22. Conti….
• Vomer The vomer is a 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.
• Palatine bones 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.
• Inferior conchae 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.

23. • Mandible This is the only movable bone of the skull. It originates as
two parts which unite at the midline. Each half consists of two main
parts: a curved body with the alveolar ridge containing the lower
teeth and a ramus which projects upwards almost at right angles to
the posterior end of the body.
• At the upper end the ramus divides into the condi/lar process which
articulates with the temporal bone to form the temporomandibular
joint and the coronoid process that gives attachment to muscles and
ligaments. The point where the ramus joins the body is the angle of
the jaw.

24. Conti….
Hyoid bone
This is an isolated horse-shoe-shaped bone lying in the soft tissues of
the neck just above the larynx and below the mandible . It does not
articulate with any other bone but is attached to the styloid process
of the temporal bone by ligaments. It gives attachment to the base
of the tongue.
The functions of hyoid bone are:
• to give resonance to the voice
• to lighten the bones of the face and cranium, making it easier for
the head to balance on top of the vertebral column.

25. Conti….
• Fontanelles of the skull At birth, ossification of the cranial sutures is
incomplete.
• Where three or more bones meet there are distinct membranous
areas, or fontanelles. The two largest are the anterior fontanelle, not
fully ossified until the child is 12 to 18 months old, and the posterior
fontanelle, usually ossified 2 to 3 months after birth. The skull bones
do not fuse before birth to allow for moulding of the baby's head
during its passage through the birth canal.

26. Vertebral column
• The vertebral column consists of 24 separate movable, irregular
bones, the sacrum (five fused bones) and the coccyx (four fused
bones). The 24 separate bones are in three groups:
• 7 cervical, 12 thoracic and 5 lumbar.
• The movable vertebrae have many characteristics in common but
some groups have distinguishing features.

27. Conti….
Thoracic vertebrae
The bodies and transverse processes have
facets for articulation with the ribs.

29. Parts of typical vertebra
Vertebrae typically consist of a body, a vertebral arch, and
several processes.
Body The body, the thick, disc-shaped anterior portion, is the
weight bearing part of a vertebra. The anterior and lateral
surfaces contain nutrient foramina, openings through which
blood vessels deliver nutrients and oxygen and remove carbon
dioxide and wastes from bone tissue.
Vertebral Arch Two short, thick processes, the pedicles , project
posteriorly from the vertebral body to unite with the flat
laminae, to form the vertebral arch.
Processes Seven processes arise from the vertebral arch.

30. Conti….

31. Cervical vertebrae
• The cervical spine has 7 distinct vertebrae called vertebrae, labeled
C1 through C7. The top of the cervical spine connects to the skull,
and the bottom connects to the upper back at about shoulder level.
• The cervical spine consists of seven, two of which are given unique
names: the first cervical vertebrae (C1) is known as the atlas, and
the second cervical vertebrae (C2) is known as the axis differ from
the other vertebrae because they are designed specifically for
rotation.
• These two cervical vertebrae support the neck to rotate in so many
directions.
• Each vertebra has a large hole (vertebral foramen) for the spinal
cord to pass through. Together, these vertebrae keep the spinal
cord shielded inside a bony tunnel called the spinal canal.

32. Conti….
• The cervical spine handles a heavy load, as the head weighs
on average between 10 and 13 pounds.
• In addition to supporting the head, the cervical spine allows
for the neck’s flexibility and head’s range of motion.
• Small holes (foramina in the transverse processes) in the
cervical spine provide a passageway for vertebral arteries to
carry blood to the brain.
• These openings for the blood vessels are present only in the
vertebrae of the cervical spine from C1 down to C6 (not in
C7 or lower).

34. Features of Vertebral Column
Intervertebral discs
• The bodies of adjacent vertebrae are separated by intervertebral
discs, consisting of an outer rim of fibrocartilage (annulus fibrosus)
and a central core of soft gelatinous material (nucleus pulposus).
They are thinnest in the cervical region and become progressively
thicker towards the lumbar region.
• The posterior longitudinal ligament in the vertebral canal helps to
keep them in place. They have a shock-absorbing function and the
cartilaginous joints they form contribute to the flexibility of the
vertebral column as a whole.

35. Thoracic Region
• Thoracic vertebrae (T1–T12) are considerably larger and stronger
than cervical vertebrae. In addition, the spinous processes on T1 and
T2 are long, laterally flattened, and directed inferiorly. In contrast,
the spinous processes on T11 and T12 are shorter, broader, and
directed more posteriorly.
• Compared to cervical vertebrae, thoracic vertebrae also have longer
and larger transverse processes. The feature of the thoracic
vertebrae that distinguishes them from other vertebrae is that they
articulate with the ribs. Except for T11 and T12, the transverse
processes have facets for articulating with the tubercles of the ribs.
The bodies of thoracic vertebrae also have either facets or
demifacets (half facets) for articulation with the heads of the ribs.
• The articulations between the thoracic vertebrae and ribs, called
vertebrocostal joints, occur on both sides of the vertebral body.

37. Lumbar Region
• The lumbar vertebrae are bones that make up the spinal column or
backbone, specifically within the lower back.
• These bones are below the cervical and thoracic vertebrae but above
the sacrum or pelvis.
• They are the largest of the unfused vertebrae, and are larger than
the bones located above.
• There are five lumbar vertebrae in humans, referred to as L1 through
L5. L1 is closest to the thoracic vertebrae, while L5 is adjacent to the
pelvis.
• The lumbar vertebrae’s function is to support the great weight of the
body and allow certain movements, such as lifting objects.

38. Conti….
• The lumbar vertebrae flex and extend through rotation
between the vertebrae and movements in the sagittal
plane between them.
• These bones also protect the spinal cord and nerves from
injury and provide a measure of support.
• The lumbar vertebrae are the biggest vertebral bones.
• They increase in size further down the spine in order to
support the increasing weight of the body.

40. Sacrum
• The sacrum is a triangular bone formed by the union of five sacral
vertebrae (S1–S5).
• The sacral vertebrae begin to fuse in individuals between 16 and 18
years of age, a process usually completed by age 30. Positioned at
the posterior portion of the pelvic cavity medial to the two hip
bones.
• The sacrum is located in between the right and left iliac bones (hips)
and forms the back of the pelvis.
• The sacrum, along with the coccyx and 2 sacroiliac joints make up
the pelvic girdle.

42. Coccyx
• The coccyx, like the sacrum, is triangular in shape. It is formed by the
fusion of usually four coccygeal vertebrae. The coccygeal vertebrae
fuse somewhat later than the sacral vertebrae, between the ages of
20 and 30.
• On the lateral surfaces of the coccyx are a series of transverse
processes; the first pair are the largest. The coccyx articulates
superiorly with the apex of the sacrum. In females, the coccyx points
inferiorly to allow the passage of a baby during birth; in
males, it points anteriorly.
• The coccyx, commonly known as the tailbone.
• Both structures (sacrum and coccyx) are weight-bearing and integral
to functions such as walking, standing and sitting.

43. Functions of the vertebral column
• Collectively the vertebral foramina form the vertebral canal which
provides a strong bony protection for the delicate spinal cord lying
within it.
• The pedicles of adjacent vertebrae form intervertebral foramina,
one on each side, providing access to the spinal cord for spinal
nerves, blood vessels and lymph vessels.
•The numerous individual bones enable a certain amount of
movement.
• It supports the skull.
• The intervertebral discs act as shock absorbers, protecting the brain.
• It forms the axis of the trunk, giving attachment to the ribs, shoulder
girdle and upper limbs, and the pelvic girdle and lower limbs.

44. Functions of the vertebral column
• Collectively the vertebral foramina form the vertebral canal which
provides a strong bony protection for the delicate spinal cord lying
within it.
• The pedicles of adjacent vertebrae form intervertebral foramina,
one on each side, providing access to the spinal cord for spinal
nerves, blood vessels and lymph vessels.
•The numerous individual bones enable a certain amount of
movement.
• It supports the skull.
• The intervertebral discs act as shock absorbers, protecting the brain.
• It forms the axis of the trunk, giving attachment to the ribs, shoulder
girdle and upper limbs, and the pelvic girdle and lower limbs.

45. Thoracic cage
• The term thorax refers to the entire chest.
• The thoracic cage (rib cage) forms the thorax (chest) portion
of the body.
• The costal cartilages attach the ribs to the sternum.
• The thoracic cage is narrower at its superior end and
broader at its inferior end and is flattened from front to
back.
• It encloses and protects the organs in the thoracic like heart
and lungs, provides support for the bones of the upper
limbs.
• It also plays a role in breathing.

46. Thoracic cage
• The bones of the thorax or thoracic cage are:
• 1 sternum
• 12 pairs of ribs
• 12 thoracic vertebrae
• Sternum or breast bone
Strenum (15cm long) consists of three parts. The superior part is the manubrium,
the middle and largest part is the body; and the inferior, smallest part is the
xiphoid process.
This flat bone also known as breast bone can be felt just under the skin in the
middle of the front of the chest. The manubrium is the uppermost section and
articulates with the clavicles at the sternoclavicular joints and with the first two
pairs of ribs. The body or middle portion gives attachment to the ribs.
The xiphoid process is the tip of the bone. It gives attachment to the diaphragm,
muscles of the anterior abdominal wall and the linea alba.

47. •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 through seventh pairs of ribs have a direct anterior
attachment to the sternum by a strip of hyaline cartilage called
costal cartilage.

48. Conti….
• The costal cartilages contribute to the elasticity of the thoracic cage and prevent
various blows to the chest from fracturing the sternum and/or ribs.
• The ribs that have costal cartilages and attach directly to the sternum are called
true (vertebrosternal) ribs.
• The first rib does not move during respiration.
• The spaces between the ribs are occupied by the intercostals muscles. During
inspiration, when these muscles contract, the ribs and sternum are lifted upwards
and outwards, increasing the capacity of the thoracic cavity.
• The remaining five pairs of ribs are termed false ribs because their costal
cartilages either attach indirectly to the sternum or do not attach to the sternum
at all. The cartilages of the eighth, ninth, and tenth pairs of ribs attach to one
another and then to the cartilages of the seventh pair of ribs. These false ribs are
called vertebrochondral ribs.
• The eleventh and twelfth pairs of ribs are false ribs designated as floating
(vertebral) ribs because the costal cartilage at their anterior ends does not attach
to the sternum at all

49. Conti….

50. References
• Essentials of Medical Physiology by K. Sembulingam and P.
Sembulingam. Jaypee Brothers Medical Publishers, New Delhi.
• Anatomy and Physiology in Health and Illness by Kathleen J.W. Wilson,
Churchill Livingstone, New York.
• Physiological basis of Medical Practice-Best and Tailor. Williams and
Wilkins Co, Riverview, MI USA.
• Text book of Medical Physiology- Arthur C, Guyton and John.E. Hall.
Miamisburg, OH, U.S.A.
• Principles of Anatomy and Physiology by Tortora Grabowski. Palmetto,
GA, U.S.A.
• Human Physiology (vol 1 and 2) by Dr. C.C. Chatterrje, Academic
Publishers Kolkata.

51. Questions
• Classify bones.
• Write about various types of bones.
• Classify the bones of axial akeletal system.
• Draw a neat and clean diagram of skull and mentions various types of
bones in skull along with their functions.
• What are the various functions of bones?
• Enlist the bones of face along with their functions.

53. THANKS