Identification of axial bones
Background:
The hard external and internal structure of our body constitutes the skeleton. The skeleton which is external is known as the exoskeleton. For example nails, hair, etc. The endoskeleton consists of those hard parts which are present inside the body of the animal.
Functions Of Skeleton:
The main functions of the endoskeleton are as follows
1) Support: One of the main functions of the skeleton is to give support to the softer body parts.
2) Protection: The endoskeleton protects the delicate body parts.
3) Muscle attachment: The endoskeleton parts provide attachment for large muscles.
4) Movement: Due to the contraction of muscles, the bones or parts of the bones are able to
change their position. Thus, the bones help in bringing about movement also.
5) Body form: It forms a typical body shape and form of an individual animal.
6) Blood cell formation: The red blood corpuscles and white blood corpuscles and platelets are produced by the bone marrow.
7) Mineral reservation: The bones maintain the phosphorus and calcium level of the blood.
8) Helps in breathing and hearing: The cartilage of the larynx, trachea, sternum and ribs are helpful in breathing while the ear bones of the middle ear transmit sound vibration from the tympanic membrane to the internal ear.
On the basis of the position of the skeletal structure of the body, the endoskeleton is divisible into two parts:
i. Axial Skeleton
ii. Appendicular skeleton
Requirement:
Skeletal system model.
Definition of an axial skeleton:
It is present on the median longitudinal axis of the body. It consists of the skull, vertebral column, sternum, and ribs. It includes 80 bones which are as follows
SKULL
The Skeleton of the head is called the skull. It rests upon the upper end of the vertebral column. Its bony structure consists of the following parts:
a) Bones of Cranium:
The cranium is formed by 8 bones.
The bones which form the cranium are- 1 frontal bone, 2 parietal bones, 2 temporal bones, 1 occipital bone, 1 sphenoid bone and 1 ethmoid bone.
The frontal bone is the bone of the forehead. This is involved in the formation of orbital cavities and the prominent ridges above the eye. The parietal bones are two in number and form the sides as well as the skull. The temporal bones lie on each side of the head. The occipital bone forms the back of the head. The sphenoid bone is a bat-shaped bone with its wings outstretched and it occupies the middle portion of the base of the skull. The ethmoid bone occupies the anterior part of the base of the skull.
b) Ear Ossicles:
There are present 6 ear ossicles in the skull- 2 malleus (Hammer shaped), 2 incus (Anvil shaped) and 2 stapes (Stirrup shaped).
c) Hyoid Bone:
One in number. This is an isolated horseshoe-shaped bone. It provides support and protection to the throat.
d) Bones Of The Face:
There are 14 bones which form the skeleton of the face- 2 zygomatic bones, 2 maxilla, 2 nasal bones, 2 lacrimal bones, 1 vomer, 2 palatine bones, 2 inferior nasal conchae, 1 mandible. Zygomatic bone forms the cheek.
Maxilla forms the upper jaw. Nasal bones form the lateral and superior surfaces of the bridge of the nose.
Lacrimal bones lie in the posterior and lateral position to the nasal bones. The vomer is a thin flat bone that extends upward from the middle of the hard palate and separates the two nasal cavities.
Palatine bones are “L” shaped bones which form the posterior part of the hard palate. The two nasal conchae form the lateral part of the nasal cavity. The mandible is one of the strongest bones of the body and is the only movable bone of the skull
VERTEBRAL COLUMN (Back Bone)
The vertebral column is about 71 cm long. It lies in the mid-dorsal line of the neck and trunk. It is made up of 33 vertebrae. The vertebrae are grouped into 5 groups
a) Cervical Vertebrae:
Seven in number, present in the neck. The first cervical vertebra is called the atlas. The second cervical vertebra is called the axis.
b) Thoracic Vertebrae:
12 in number, present in the chest. They are larger and stronger than the cervical vertebrae.
c) Lumbar Vertebrae:
5 in number, present in the abdomen. They are the largest and strongest in the vertebral column.
d) Sacrum:
5 sacral vertebrae are fused in the adult forming one structure called the sacrum.
e) Coccyx:
The four coccygeal vertebrae are fused to form a curved triangular bone called the coccyx. It is considered a vestigial tail.
The vertebral formula of humans is C7T12L5S(5)C(4).
A typical vertebra shows the following structure:
- A body: A body is present anteriorly in each vertebra. It is smaller in the cervical region and larger towards the lumbar end.
- A neural arch: This arch encloses a large foramen called a vertebral foramen.
There is the presence of transverse processes. The spinous process projects backwards.
STERNUM ( Breast Bone)
It is a flat bone which is present in the chest. It is about 15cm long. It consists of three parts. The manubrium is the uppermost part which has articular facets laterally for articulation with the clavicle to form the sternoclavicular joint. The body is the middle portion which shows the presence of facets for articulation with ribs and the xiphoid process is the tip of the bone
RIBS
There are 12 pairs of ribs which form the bony lateral walls of the thoracic cage.
a) The first seven pairs are called true ribs. Because their anterior ends are attached directly to the sternum by means of small pieces of cartilage.
b) The eighth, ninth and tenth pairs of ribs are called false ribs. They articulate by cartilage with costal cartilage of the seventh rib and thus are attached indirectly to the sternum.
c) The last two pairs of ribs are called floating ribs because their anterior ends are not attached to either the sternum or the cartilage of another rib.
The rib is a flat bone and presents a head (articulate with the body of vertebra), neck (constricted part between head and tubercle), Tubercle ( articulates with thoracic vertebra), and Angle (the point at which the bone ends).
Human Anatomy and Physiology Practical Syllabus
First Year B Pharm Notes, Syllabus, Books, PDF Subjectwise/Topicwise
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Understanding Sex and Gender: A Complex Tapestry
Endometriosis: A Silent Struggle
Ozempic: A Closer Look at Potential Side Effects
