1.💗BONE AS AN ORGAN. STRUCTURE OF MATURE BONE: OSSEOUS TISSUE, COMPACT AND SPONGY BONE TISSUE. TYPES OF BONES. THE SKELETON – DEFINITION, FUNCTION💗

How many bones are in an adult human skeleton?

206

How many bones are in a fetal skeleton?

275

Into what two groups can the skeleton be divided?

Axial and Appendicular

What bones are included in the axial skeleton?

- Skull
- Vertebral columns
- Ribs and sternum
- Cranium
- Spine
- Atlas and axis

What bones are included in the appendicular skeleton?

- Upper and lower limbs
- Scapula
- Clavicle
- Pelvic girdle
- Pectoral girdle
- Hip bone

What is the definition of the skeleton?

A hard framework consisting of inorganic material that supports and protects the soft parts/internal organs of an animal and serves as an attachment for muscles.

What are the functions of the skeleton?

- Movement: Bones act as a lever and form joints allowing muscles to pull on them and produce joint movements.
- Support: Protects organs within the human body (e.g., cranium protects the brain, vertebrae protect the spinal cord).
- Production of blood cells: Certain bones contain red marrow and produce RBCs, WBCs, and platelets (e.g., pelvis, sternum).
- Storage of minerals: Acts as a mineral store for calcium and phosphorus, released when needed.
- Attachment: Serves as attachment for muscles.

What is bone the primary site of?

haematopoiesis

What are the four types of bone cells?

- Osteoblasts (bone forming cells)
- Osteoclasts (bone reabsorbing cells)
- Osteocytes (mature bone cells)
- Osteogenic cells (divide into osteoblasts to form new bones)

What is compact bone?

- Dense bone surrounded by spongy bone, homogenous, hard outer layers, lacks spaces between lamellae

What is spongy bone?

- Contains blood, forms cells, has many opening spaces between lamellae, more porous inner layers of bone

What are examples of long bones?

- Metacarpals
- Metatarsals
- Humerus

What are examples of short bones?

- Carpals
- Tarsals

What are examples of flat bones?

- Rib
- Scapula
- Skull
- Sternum

What are examples of irregular bones?

- Vertebrae
- Some facial bones

What is an example of a sesamoid bone?

Patella

What are the main sections of a bone?

Diaphysis and epiphysis

What is the diaphysis?

- Hollow, tubular shaft that runs between proximal and distal ends of bone, contains medullary canal (filled with yellow bone marrow in adults) with outer walls composed of dense and hard compact bone

What is the epiphysis?

- Wider section filled with spongy bone, meets with diaphysis at metaphysis

What is the metaphysis?

- Contains the epiphyseal plate, the site of long bone elongation

What is the endosteum?

- Lining adjacent to the medullary canal, consisting of bone cells that allow bone to grow, repair, and remodel

What is the periosteum?

- The double layer of cells on the outside layer of bone, containing blood vessels, lymphatic vessels, and nerves to nourish compact bone

What secures the periosteum to the underlying bone?

- Sharpey's fibers

What is cortical bone?

- Consists of lamellae, which are concentric layers of mineralized bone

What is trabecular bone?

- Can be spongy with a lattice structure

What is bone marrow composed of?

- Stroma
- Myeloid tissue
- Fat and lymphatic tissue

What are the two types of bone marrow and their functions?

- Red bone marrow: RBC production and hematopoietic tissue
- Yellow bone marrow: Less vascularized, contains a large number of fat cells

What do the vessels in bones do?

- Supply bones, muscles of the skeletal system, and joints with blood