Bones and Skeletal System Anatomy

• The skeletal system is made of bones, cartilages, and joints.

Human Anatomy

• Anatomy in Greek means "to cut."
• Anatomy in Latin means "to dissect."

Levels of Studying Anatomy

• Macroscopic or gross anatomy studies large visible structures.
• Microscopic anatomy, also known as histology, studies structures at a microscopic level.
• Radiological anatomy uses imaging techniques like X-rays to study anatomy.

Anatomical Planes

• Sagittal (Longitudinal) Plane: Divides the body into right and left halves.
  • The median plane divides the body into equal right and left halves.
• Coronal (Frontal) Plane: Divides the body into anterior and posterior sections.
• Transverse (Axial) Plane: Divides the body into upper and lower parts.

Anatomical Terms of Position

• Superior: towards the head
• Inferior: away from the head
• Anterior (Ventral): towards the front
• Posterior (Dorsal): towards the back
• Medial: towards the midline
• Lateral: away from the midline
• Proximal: closer to the origin of the body part
• Distal: farther from the origin of the body part
• External (Outer): located on the outside
• Internal (Inner): located on the Inside
• Superficial: closer to the surface
• Deep: away from the surface

The Skeletal System

• The skeleton represents 20% of body weight and includes axial and appendicular subdivisions.

Axial Skeleton

• The axial skeleton lies along the central axis of the body.
• It is formed by the skull, vertebral column, and bones of the thoracic cage.

Appendicular Skeleton

• Consists of bones of the upper and lower limbs.
• Includes the shoulder and pelvic girdles.

The Skull

• The skull has cranial and facial portions.
• The cranial portion is made of 8 bones, and the facial portion is made of 14 bones.
• The base of the skull holds the foramen magnum for spinal cord passage and multiple small foramina for nerves and blood vessels.
• The anterior view of the skull contains the openings and cavities for the orbit, the nose, and the mouth.
• The fetal skull bones are connected via membranes termed fontanels and these allows for growth with age.
• The skull features paranasal air sinuses.
  • These sinuses reduce skull weight.
  • Sinusitis is Clinical anatomy.

Cranial Portion

• Composed of 8 flat bones articulated with non-mobile strong fibrous joints called sutures.
• It includes one frontal bone, one occipital bone, one sphenoid bone, one ethmoid bone, two parietal bones, and two temporal bones.

Facial Portion

• Formed of 14 flat irregular bones joined by sutures including two nasal bones, two zygomatic bones, two maxillary bones, two lacrimal bones, two palatine bones, two inferior nasal conchae, one vomer, and one mandible.

The Vertebral Column

• It supports the head, encloses the spinal cord, and transmits body weight.
• It is formed of separate vertebrae and some are fused.
• There are 33 vertebrae divided into 5 groups: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused into a single bone called sacrum), and 4 coccygeal (fused in a single bone called coccyx).
• Each vertebra contains the vertebral body and anterior.
• The vertebral arch is posterior.
• Superior and inferior articular processes.
• Each vertebra has a vertebral foramen that allows passage of the spinal cord
• The vertebrae are articulated with each other by the inter vertebral discs

Characteristics of Vertebrae

• Cervical vertebrae feature a bifid spinous process.
  • C1 is called atlas.
  • C2 is called axis.
• Thoracic vertebrae has articular surfaces for rib articulation on the body and transverse processes.
• The lumbar vertebrae is the largest and has a kidney shaped body.

Thoracic cage

• Formed of the sternum anteriorly, 12 thoracic vertebrae posteriorly, and 12 pairs of ribs.
• 12 pairs of ribs

Sternum

• This is a flat bone with three parts:
  • Manubrium.
  • Body.
  • Xiphoid process.

Ribs

• There are three groups: True ribs (1st-7th) articulate with the sternum anteriorly and thoracic vertebrae posteriorly False ribs (8th, 9th, and 10th) attach to each other anteriorly but articulate posteriorly to the thoracic vertebrae Floating ribs (11th, 12th) articulate posteriorly to the thoracic vertebrae but are free anteriorly.

Appendicular Skeleton

Shoulder Girdle

• It is formed of 2 bones, the clavicle anteriorly, and the scapula posteriorly.

Pelvic Girdle

• Formed of the right and left hip bones.
• Each hip bone is formed of three fused bones: ilium, pubis, and ischium.
• Bones of the Free Upper Limb

Humerus

• Known to be in the arm

Radius and Ulna

• Located in the forearm

Carpal Bones

• It has 8 small irregular bones in the wrist

Metacarpal Bones

• Known to be in the hand

Phalanges

• It contains 14 short irregular bones in the finger.
• Bones of the Free Lower Limb

Femur

• It is located in the thigh

Tibia and Fibula

• It is located in the leg

Tarsal Bones

• It has 7 irregular bones in the heel and ankle.

Metatarsal Bones

• Contains 5 bones

Phalanges

• The structure has 14 bones in the toes (digits).

Classification of Bones

Classified on the Basis of Shape:

• Long bones include the humerus, femur, tibia, fibula, radius, and ulna.
• Short bones are the carpals and tarsals of the hands and feet.
• Irregular bones include vertebrae.
• Flat bones include the scapula, sternum, hip, and bones of the skull.
• Sesamoid bones, the largest of which is the patella.

Functions of Bones

• Supports the body
• Protects soft organs.
• Movement due to attached skeletal muscles (passive)
• Stores minerals and fats.
• Responsible for blood cell formation.

Explore bone classification, function, and anatomical location within the skeletal system. This includes types of bones like sesamoid and their functional significance. Understand how bone damage affects movement.