Anatomy & Histology (Bio-3122)

Level-3 (Pharmaceutical Biotechnology);

Lecture 3
Title: Skeletal System (Axial Skeleton)
18/10/2023
Assoc. Prof. / Reda M. Mansour
reda.mansour@buc.edu.eg
Office : 235 Biotechnology

Office Hours: Wednesday 2:00 pm to 4:00 pm

Text Books
1- Drake, R.L; Vogl, A.W.; Mitchel, A.W.M. (2003): Grayʼs Human Anatomy. Churchill Livingstone, Elsevier, Inc.
2- Hansen, J.T. (2010): Netterʼs Clinical Anatomy. Saunders, Elsevier Inc.
3- Scanlon, V.C. and Sanders, T (2019): Essentials of Anatomy & Physiology (8th edition). Davis Company.
Philadelphia
Skeletal System
(Axial Skeleton)
 The human skeleton

Bones of the appendicular

The human skeleton Bones of the axial skeleton include the
contains 206 bones: 80 skeleton include the clavicle, scapula, humerus,
form the axial skeleton facial and cranial bones, radius, ulna, metacarpals,
and 126 form the hyoid bone, vertebrae, pelvic bone, femur, patella,
appendicular skeleton. ribs, and sternum. fibula, tibia, and
metatarsals.
* Bone classification:
Bones are typically classified by shape. Thus, bones may be;
1. long (such as the humerus, radius, femur, and tibia),
2. short (such as the carpals and tarsals),
3. flat (such as the scapula, ribs, and skull),
4. irregular (such as the vertebrae and mandible),
5. sesamoid (such as the patella).
Bone functions:
Bones perform various anatomic (mechanical) and physiologic functions:
1. They protect internal tissues and organs; for example, the 33 vertebrae surround
and protect the spinal cord.
2. They stabilize and support the body.
3. They provide a surface for muscle, ligament, and tendon attachment.
4. They move through “lever” action when contracted.
5. They produce red blood cells in the bone marrow (a process called
hematopoiesis).
6. They store mineral salts—for example, approximately 99% of the body’s calcium.
 Joints
Joints (articulations) are points of contact between two bones that hold the bones
together. Many joints also allow flexibility and movement. Joints can be classified
by function (extent of movement) or by structure.
I- Functional classification:
1- Immovable joints (synarthrosis or fibrous joints) include skull sutures,
articulations between teeth and mandible or maxilla (gomphoses), and joint
between tibia and fibula (syndesmosis).
2- Slightly movable or immovable (amphiarthrosis or Cartilaginous joints) include
joint between 1st pair of ribs and sternum (synchrondosis) and the pubic
symphysis of the pelvic girdle.
3- Freely movable joints (diarthrosis or Synovial joints) Examples of these include
the elbow, shoulder, and ankle.
Only for reading Synovial joints:
Contiguous bony surfaces in the synovial joints are covered by articular cartilage
and joined by ligaments lined with synovial membrane.
Freely movable, synovial joints include most joints of the arms and legs.
Other features of synovial joints include:
joint cavity, a potential space that separates the articulating surfaces of the two
bones
articular capsule—a saclike envelope whose outer layer is lined with a vascular
synovial membrane
synovial fluid—a viscid fluid, produced by the synovial membrane, that lubricates
the joint reinforcing ligaments consisting of fibrous connective tissue, which
connect bones within the joint and reinforce the joint capsule.
Based on their structure and the type of movement they allow, synovial joints fall
into various subdivisions— gliding, hinge, pivot, condylar, saddle, and ball-and-
socket.
Only for reading
 Skeletal System Anatomy
This skeletal system can be divided into the axial and appendicular systems. In an
adult body, it is mainly composed of 206 individual bones which are organized into
two main divisions:
1- Axial skeleton
2- Appendicular skeleton (next lecture).
1- Axial skeleton: The axial skeleton is composed of 80 bones and it consists of:
1. Skull Bone: It includes 8 cranial bones, 14 facial bones, 6 auditory ossicles, and
the Hyoid Bone: support tongue
2. The bone of the thoracic cage: It includes 25 bones of the thorax- a breastbone
and 24 ribs.
3. The bone of the vertebral column: It includes 24 vertebrae bones, the sacrum
bone, and the coccyx bone.
The Skull and Associated Bones
 The Skull and Associated Bones
The skull consists of 8 cranial bones and 14 facial bones. Also in the head are 3
small bones in each middle ear cavity and the hyoid bone that supports the base of
the tongue.
The cranial bones form the braincase (lined with the meninges) that encloses and
protects the brain, eyes, and ears.
These are the frontal bone, parietal bones (two), temporal bones (two), and
occipital bone. The sphenoid bone and ethmoid bone are part of the floor of the
braincase and the orbits (sockets) for the eyes.
The frontal bone forms the forehead and the anterior part of the top of the skull.
Parietal means “wall,” and the two large parietal bones form the posterior top and
much of the side walls of the skull. Each temporal bone on the side of the skull
contains an external auditory meatus (ear canal), a middle ear cavity, and an inner
ear labyrinth.
• The occipital bone forms the lower, posterior part of the braincase. Its foramen
magnum is a large opening for the spinal cord, and the two condyles (rounded
projections) on either side articulate with the atlas, the first cervical vertebra.
• The sphenoid bone is said to be shaped like a bat, and the greater wing is visible
on the side of the skull between the frontal and temporal bones. The body of the
bat has a depression called the sella turcica, which encloses the pituitary gland.
• The ethmoid bone has a vertical projection called the crista galli (“rooster’s
comb”) that anchors the cranial meninges. The rest of the ethmoid bone forms
the roof and upper walls of the nasal cavities, and its perpendicular plate forms
the upper part of the nasal septum.
All of the joints between cranial bones are immovable joints called sutures. It may
seem strange to refer to a joint without movement, but the term joint (or
articulation) is used for any junction of two bones.
Sutures of the Skull
The boundaries between skull bones are immovable joints called sutures.
The lambdoid suture, separating the occipital bone from the parietal bones.
The coronal suture, separating the anterior frontal bone from the more posterior
parietal bones.
the sagittal suture begins at the superior midline of the lambdoid suture and
extends anteriorly between the parietal bones to the coronal suture
Lateral view of the bones of
the adult skull
 Anterior view of the
bones of the adult skull

Only for reading

Only for reading

Inferior view
of skull,
mandible
removed
Sectional Anatomy of the Skull, Part I. Horizontal section: A superior view showing major landmarks in the floor of the cranial
cavity.

Only for reading

Sectional Anatomy of the Skull, Part II. Sagittal section: A medial view of the right half of the skull. Because the bony nasal
septum is intact, the right nasal cavity cannot be seen.
Only for reading
 Facial Bones
The Maxillae: The left and right maxillae, or maxillary bones, are the largest facial
bones and form the upper jaw.
The Palatine Bones: form the posterior portions of the bony palate and contribute
to the floor of the orbit.
The Nasal Bones: The paired nasal bones articulate with the frontal bone at the
midline and articulate with cartilages that form the superior borders of the
external nares.
The Inferior Nasal Conchae: One inferior nasal concha is located on each side of
the nasal septum, attached to the lateral wall of the nasal cavity. They increase
the epithelial surface area and create turbulence in the inspired air. The superior
and middle conchae of the ethmoid perform the same functions.
The Zygomatic Bones: The temporal process of the zygomatic bone articulates
with the zygomatic process of the temporal bone to form the zygomatic arch
The Lacrimal Bones: The paired lacrimal bones are the smallest bones in the skull.
They are situated in the medial portion of each orbit. Each lacrimal bone forms a
lacrimal groove with the adjacent maxilla, and this groove leads to a nasolacrimal
canal that delivers tears to the nasal cavity.
The Vomer: The vomer forms the inferior portion of the nasal septum. It is based
on the floor of the nasal cavity and articulates with both the maxillae and the
palatines along the midline.
The Mandible: The mandible is the entire lower jaw. It articulates with the
temporal bone at the temporomandibular joint.
Only for reading
Orbital and Nasal Complexes and the Hyoid Bone
The Orbital Complex: Seven bones form the orbital complex, a bony recess that
contains an eye: frontal, lacrimal, palatine, and zygomatic bones and the ethmoid,
sphenoid, and maxillae.
The Nasal Complex: The nasal complex includes the bones and cartilage that
enclose the nasal cavities and the paranasal sinuses. Paranasal sinuses are hollow
airways that interconnect with the nasal passages. Large paranasal sinuses are
present in the frontal bone and the sphenoid, ethmoid, and maxillae.
The Hyoid Bone: The hyoid bone, suspended by stylohyoid ligaments, consists of a
body, the greater horns, and the lesser horns. The hyoid bone serves as a base for
several muscles concerned with movements of the tongue
and larynx.
The Skulls of Infants, Children, and Adults
● Fibrous connections at fontanels permit the skulls of infants and children to
continue growing.