The Skeletal System

• The human skeleton consists of 206 named bones
• Bones of the skeleton are grouped into two principal divisions:
• Axial skeleton
• Consists of the bones that lie around the longitudinal axis of the human body: Skull bones, auditory ossicles (ear bones), hyoid bone, ribs, sternum (breastbone), and bones of the vertebral column.
• The primary function is protection of vital organs.
• Appendicular skeleton
• Consists of the bones of the upper and lower limbs (extremities), plus the bones forming the girdles that connect the limbs to the axial skeleton. The primary function of this division is movement.

Divisions of the Skeletal System

Bones of the Human Body

Bone Tissue

Bone is a specialized type of connective tissue characterized by the presence of a calcified extracellular matrix (called bone matrix) and three types of cells: Osteoblasts, Osteocytes and Osteoclasts.

Functions of bones:

1. Support fleshy structures.
2. Protect vital organs (example: skull protect the brain).
3. Assist in movement.
4. Synthesis of blood element.
5. Storage of fat.
6. Storage of minerals (calcium and phosphate).

Cells of bones:

Multinucleated

Bone remodelling

Bone matrix:

• Bone matrix is formed of various organic and inorganic molecules.
• Collagen fibers is abundant in bone matrix.

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Periosteum:

• A thick connective tissue layer that covers the bone.
• It’s important for the nourishment of bone, in the formation of bone and in fracture repair.

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Endosteum:

• A thin connective tissue layer that lines the cavities inside the bone.

Calcium hydroxyapatite: most abundant inorganic material

Osteoprogenitor cells

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Classification of bones

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• In a cross section two forms appear:
• Compact (cortical) bone: a dense area with generally no cavities.
• Cancellous (trabecular or spongy) bone: have several interconnected cavities.
• Histologically, both the compact bone and the trabeculae of the spongy bone have the same features (lamellar bone).

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According to Gross Morphology:

According to Histological Features:

• Primary (woven) bone in which the collagen fibers of the matrix have no specific arrangement.

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• Secondary (lamellar) bone in which the collagen fibers are arranged in layers called lamellae.

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• In secondary bone, the lamellae usually form concentric circles around a central cavity in what’s called Osteons.

An osteon is formed of:

1. Central Canal: this contains blood vessels, nerves and loose connective tissue.
2. Several concentric lamellae.
3. Several lacunae containing osteocytes and located between the lamellae.
4. Several canaliculi that connect the lacunae together.

• Bones can be classified into five types based on shape:
• Long
• Short
• Flat
• Irregular
• Sesamoid

According to Shape:

• Long Bones
• Greater length than width and are slightly curved for strength
• Femur, tibia, fibula, humerus, ulna, radius, phalanges
• Short bones
• Cube-shaped and are nearly equal in length and width
• Carpal, tarsal
• Flat bones
• Thin and composed of two nearly parallel plates of compact bone tissue enclosing a layer of spongy bone tissue
• Cranial, sternum, ribs, scapulae
• Irregular bones
• Complex shapes and cannot be grouped into any of the previous categories
• Vertebrae, hip bones, some facial bones, calcaneus
• Sesamoid bones
• Protect tendons from excessive wear and tear
• Patellae, in foot, in hand

Various parts of long bones.

Upper End

Lower End

Shaft

• Bones have characteristic surface markings
• Structural features adapted for specific functions
• There are two major types of surface markings:
• 1) Depressions and openings
• Allow the passage of blood vessels and nerves or form joints
• 2) Processes
• Projections or outgrowths that form joints or serve as attachment points for ligaments and tendons

Bone Surface Markings

• The Axial Skeleton

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ااااااعلان هام جداااااا

الى طلبة تشريح إنسان سيكون الامتحان الاول للفصل الدراسي الاول

2016-2017

يوم الاحد الموافق

23/10/2016

الساعة 11-12 ظهرا

المكان : محتبرابن حيان

نتمنى لكم النجاح

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• The skull (Cranium) Consists of 22 bones
• Bones of the skull are grouped into two categories:
1. Cranial bones
• Eight cranial bones form the cranial cavity
• Frontal bone, two parietal bones, two temporal bones, the occipital bone, the sphenoid bone, ethmoid bone

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• Facial bones
• Fourteen facial bones form the face
• Two nasal bones, two maxillae, two zygomatic bones, the mandible, two lacrimal bones, two palatine bones, two inferior nasal conchae, vomer

The Skull

• The cranial and facial bones protect and support special sense organs and the brain
• Besides forming the large cranial cavity, the skull also forms several smaller cavities
• Nasal cavity
• Orbits (eye sockets)
• Paranasal sinuses
• Small cavities which house organs involved in hearing and equilibrium

Features of the Skull

• Immovable joints called sutures fuse most of the skull bones together
• The skull provides large areas of attachment for muscles that move various parts of the head
• Skull and facial bones provide attachment for muscles that produce facial expressions
• The facial bones form the framework of the face and provide support for the entrances to the digestive and respiratory systems

Cranial Bones:

• Frontal Bone
• Forms the forehead
• Parietal Bones
• Form the sides and roof of the cranial cavity
• Temporal Bones (Zygomatic process and Mandibular fossa of TMJ
• Form the lateral aspects and floor of the cranium
• Consists of 5 parts: squamous part, petrous part, tympanic part, mastoid part and the styloid process

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• Occipital Bone (foramen magnum?)
• Forms the posterior part and most of the base of the cranium
• The perceptible protrusion on the back of the head is the external occipital protuberance

Greater wing

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Temporal & zygomatic bones

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Pterion: middle meningeal artery.

• Sphenoid Bone (optic nerve)
• Lies at the middle part of the base of the skull
• It’s formed of:
• Body (Sella turcica): contain the pituitary gland
• Lesser wings
• Greater wings
• Pterygoid processes
• Sphenoid sinus

• Ethmoid Bone (olfactory nerve)
• Located in the midline in the anterior part of the cranial floor and forms the roof of the nasal cavity

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Parts:

1. Superior and middle conchae: thin bony projections (nose)
2. Transverse plate
3. Perpendicular plate
4. Crista galli
5. Cribriform plate
6. Ethmoid sinuses

• Cribriform plate
• Crista galli

• Nasal Bones
• Form the bridge of the nose
• Maxillae
• Form the upper jawbone
• Has the following processes:
• Frontal process superiorly
• Zygomatic process laterally
• Palatine process posteriorly
• Alveolar process inferiorly. This one contains sockets for the teeth.
• The palatine process 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
• The temporal process of this bone unite with the zygomatic process of the temporal bone to form the zygomatic arch.

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Facial Bones:

Maxillae bone articulates with every bone of the face except the mandible

• 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
• Vomer
• Forms the inferior portion of the nasal septum
• Mandible
• Lower jawbone
• The largest, strongest facial bone
• The only movable skull bone

Temporomandibular joint (TMJ)

Temporal bone and the mandible

Parts of the Mandible:

TMJ

The Nasal Septum:

A partition that divides the nasal cavity into right and left halves. It’s formed of 2 bony part and 1 cartilaginous part:

• The perpendicular plate of the ethmoid bone posterior and superior
• The vomer bone posterior and inferior.
• Septal cartilage (hyaline cartilage) anteriorly.

The Orbital Cavity:

• The bones that participate in the formation of the orbital cavity are:

1-Frontal 2-Lacrimal

3-Ethmoid 4-Maxillary

5-Zygomatic 6-Sphenoid

Main Sutures:

1. Coronal Suture: between the frontal and the two parietal bones.
2. Sagittal Suture: between the two parietal bones.
3. Lambdoid Suture: between the two parietal and the occipital bones.
4. Squamous suture: Temporal and parietal

Sinusitis is an inflammation of the mucous membrane.

Paranasal Sinuses:

• Cavities within cranial and facial bones near the nasal cavity
• Secretions produced by the mucous membranes which line the sinuses, drain into the nasal cavity
• Serve as resonating chambers that intensify and prolong sounds

• Found in the following bones

1-Frontal 2-Ethmoid

3-Sphenoid 4-Maxillary

: Largest

• Areas of unossified tissue that link the cranial bones at birth
• Eventually, they are replaced with bone to become sutures
• Provide flexibility to the fetal skull, allowing the skull to change shape as it passes through the birth canal

Fontanels:

• Located in the upper part of the neck
• The only bone in the body that does not articulate with any other bone
• Supports the tongue, providing attachment sites for some tongue muscles and for muscles of the neck and pharynx and some ligaments
• Formed of body, greater horns and lesser horns

The Hyoid Bone

• Also called the spine, backbone, or spinal column
• Functions to:
• Protect the spinal cord
• Support the head
• Serve as a point of attachment for the ribs, pelvic girdle, and muscles
• Composed of a series of bones called vertebrae (Adult=26)
• 7 cervical are in the neck region
• 12 thoracic are posterior to the thoracic cavity
• 5 lumbar support the lower back
• 1 sacrum consists of five fused sacral vertebrae
• 1 coccyx consists of four fused coccygeal vertebrae

The Vertebral Column

• The vertebral column is curved to varying degrees in different locations
• Curves increase the column strength
• Help maintain balance in the upright position
• Absorb shocks during walking, and help protect the vertebrae from fracture
• These curves are:
• Cervical
• Thoracic
• Lumbar
• Sacral

• Intervertebral Discs (formed of fibrocartilage):

Found between the bodies of adjacent vertebrae and function in:

• Form strong joints
• Permit various movements of the vertebral column
• Absorb vertical shock

The Vertebrae:

Parts of vertebrae: Vertebrae typically consist of:

• A Body (weight bearing)
• A vertebral arch (surrounds the spinal cord)
• Several processes (points of attachment for muscles +)

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“Yes”

“No”

Odontoid process

• Cervical Region

Cervical vertebrae (C1–C7)

The atlas (C1) articulates with the skull (occipital)

The axis (C2) has a vertical process (Odontoid or Dens) that extends superiorly to articulate with atlas

Thoracic Region

Thoracic vertebrae (T1–T12)

Articulate with the ribs

Lumbar Region

Lumbar vertebrae (L1–L5)

Provide for the attachment of the large back muscles

Sacrum

The sacrum is a triangular bone formed by the union of five sacral vertebrae (S1–S5)

Serves as a strong foundation for the pelvic girdle

Coccyx

The coccyx, like the sacrum, is triangular in shape

It is formed by the fusion of usually four coccygeal vertebrae

• Thoracic cage is formed by the:
• Sternum
• Ribs
• Costal cartilages (attach ribs to sternum)
• Thoracic vertebrae
• Functions to:
• Enclose and protect the organs in the thoracic and abdominal cavities
• Provide support for the bones of the upper limbs
• Play a role in breathing

The Thoracic Cage

The Sternum:

• “Breastbone” located in the center of the thoracic wall
• Consists of the manubrium, body, xiphoid process

Angle of louis

2^nd rib

Level: T4&T5

Count ribs

The Ribs:

Each rib is formed of:

1. Head: which articulates with the vertebrae.
2. Neck: a constricted region immediately after the head.
3. Tubercle: this contains an articular facet for the transverse process.
4. Angle: area where the shaft bends forwards.
5. Shaft (Body).
6. Costal groove: this runs along the inferior border of the inner surface of the shaft.

• 12 pairs of ribs give structural support to the sides of the thoracic cavity
• The upper 7 pairs are called true ribs because they’re attached to the sternum through their own costal cartilage.
• Pairs 8-10 are called false ribs because they’re attached anteriorly to each other and to the seventh rib by means of their costal cartilages.
• Pairs 11 and 12 are called floating ribs because they have no anterior attachment.

The Ribs: