The Skeleton Overview

The Skeleton

• The skeleton is a type of connective tissue composed of cells, fibers, and a matrix.
• The matrix is hardened due to calcification.
• Bones have multiple functions, including supporting and protecting vital organs, enabling movement, and acting as a reservoir for ions like calcium and magnesium.
• Bones also perform hematopoietic action, meaning they contribute to the production of blood cells.

Objectives

• The lecture intends to cover the definition, functions, and classification of bones, covering diverse categories.
• Different types of bones will be discussed, categorized by location, structure, ossification method, and shape.
• The presentation will explore the anatomical layout of a typical long bone.
• The blood supply and specific parts of a long bone will be delineated.

Bone Types According to Position

• The skull is part of the axial skeleton.
• The ribs, sternum, and spine are also part of the axial skeleton.
• The clavicle and scapulae are part of the appendicular skeleton.
• The humerus, radius, and ulna are part of the appendicular skeleton.
• The femur, tibia, and fibula are part of the appendicular skeleton.
• The phalanges (fingers and toes) are part of the appendicular skeleton.
• The pelvis is part of the axial skeleton.

Axial Skeleton

• The axial skeleton forms the central axis of the body.
• It includes the skull, spine, and ribcage.
• It provides crucial support and protection for vital organs within the torso.

Skull

• The skull is the bony structure that encases the brain.
• It includes the cranium and the mandible.
• The cranium is the upper part of the skull.
• The mandible is the lower jaw.
• Further categorized parts of the skull/cranium identified are: skull cap, base of the skull and facial bones..

Vertebral Column

• The vertebral column is the spine.
• It is composed of 33 individual vertebrae, some of which fuse to form larger structures.
• The mobile vertebrae (cervical, thoracic and lumbar) are categorized by their relative location.
• The non-mobile vertebrae (sacrum and coccyx) are fused.
• The spine allows for flexion, extension, lateral flexion, and rotation..

Thoracic Cage

• The rib cage (thoracic cage) encloses the thoracic organs.
• It consists of ribs attached to the spine, connected to the sternum by cartilage, which is a crucial part of breathing.

Appendicular Skeleton

• This component comprises the bones of the limbs and their supporting structures.
• It includes the bones of the upper and lower extremities.

Bone Types According to Structure

• Cancellous bone is a spongy, porous type of bone.
• Compact bone is a dense, hard type of bone.

Bone Types According to Ossification

• Membranous bones develop directly from a sheet of connective tissue.
• Cartilaginous bones form from a cartilaginous model.

Bone Types According to Shape

• Long bones are longer than they are wide (e.g., femur).
• Short bones are roughly equal in length and width (e.g., carpal bones).
• Irregular bones have complex shapes (e.g., vertebrae).
• Flat bones are thin and flattened (e.g., skull bones).
• Sesamoid bones are small, round bones embedded within tendons (e.g., patella).
• Pneumatic bones are bones containing air-filled spaces (e.g. mastoid bone).

Basic Structure of a Bone

• The periosteum is a membrane that covers the outer surface of the bone.
• The medulla is the inner part of the bone.
• The cortex is the hard outer layer of bones, comprised of compact bone.
• The medullary cavity is the central cavity inside the bone containing bone marrow.

Parts of a Long Bone

• The diaphysis is the shaft of a long bone.
• The epiphysis are the ends of a long bone.
• The epiphyseal cartilage or line separates the diaphysis and the epiphysis.
• The metaphysis is the area between the diaphysis and the epiphysis.
• The medullary cavity contains bone marrow.
• The periosteum is a tough membrane covering the outer surface of the entire bone.

Blood Supply of a Long Bone

• Blood vessels called nutrient arteries supply blood to the medullary cavity.
• Epiphyseal, metaphysial, and periosteal arteries also supply blood to the various regions of a long bone.