Functions and Structure of Bone

Study Notes

Functions of Bone and Skeletal System

Bones provide support for the body
Protect internal organs
- The Cranium protects the brain
- Vertebrae protect the spinal cord
- Ribs protect the heart and lungs
Bones assist in movement; skeletal muscles attach to bone and contractions pull on bones producing movement.
Bones help mineral homeostasis; bone tissue stores minerals like calcium (99% of the body's content) and phosphorus, serving as a reservoir.
Bones produce blood cells in the red bone marrow (hemopoiesis) including red blood cells, white blood cells, and platelets.
Bones store triglycerides in yellow bone marrow in adipose cells which serve as a potential energy reserve.

Structure of Bone

Diaphysis is the shaft of the bone
Epiphysis is the end of the bone
Metaphysis is the area between the diaphysis and epiphysis
Epiphyseal Growth Plate is the area of growth (hyaline cartilage) in immature bone between the diaphysis and epiphysis
Articular Cartilage covers the ends of bones at joints
Periosteum is the fibrous connective tissue covering the outer surface of bone that contains perforating fibers that secure the periosteum to the bone.
Medullary Cavity is the hollow space within the diaphysis containing bone marrow
Endosteum is the thin membrane that lines the medullary cavity

Histology of Bone Tissue

Bone tissue is connective tissue with an extracellular matrix surrounding cells.
Matrix contains 25% water, 25% collagen fibers, and 50% crystallized mineral salts. The most abundant mineral salt is calcium phosphate.
Calcification is initiated by osteoblasts when mineral salts are deposited and crystalize in the collagen fiber framework of the extracellular matrix.
Collagen fibers provide flexibility to bone.
Four types of cells are present in bone tissue:
- Osteogenic Cells: Undergo cell division, developing into osteoblasts
- Osteoblasts: Bone-building cells, synthesize the extracellular matrix
- Osteocytes: Mature bone cells exchanging nutrients and waste with the blood
- Osteoclasts: Digest mineral components of bone matrix (resorption), regulating blood calcium levels

Histology of Bone Tissue - Categories and Types

Bone may be classified as compact or spongy.
Compact Bone resists stresses from weight and movement, arranged in structural units called osteons or Haversian systems.
- Osteons: Contain a central (Haversian) canal with concentrically arranged lamellae around the canal, lacunae, and osteocytes, which are connected by canaliculi.
- Canaliculi connect lacunae forming a system of interconnected canals providing routes for nutrients and oxygen to reach osteocytes.
- The osteon's organization changes with the physical demands on the skeleton.
Spongy Bone lacks osteons, lamellae arranged in a thin column lattice called trabeculae.
- Spaces between trabeculae make bone lighter and support red bone marrow.
- Hemopoiesis occurs in spongy bone.
- Trabeculae are oriented along lines of stress to help bones resist stress without breaking.
Spongy Bone is located in the epiphyses of long bones and short, flat, and irregular bones and does not contain osteons but has irregular arrangement of lamellae and osteocytes.
- Trabeculae contain osteocytes in lacunae with radiating canaliculi.

Blood and Nerve Supply of Bone

Bone is richly supplied with blood.
- Periosteal arteries accompanied by nerves supply the periosteum and compact bone.
- Epiphyseal veins carry blood away from bones.

Description

Explore the vital functions and unique structure of bones within the skeletal system. This quiz delves into how bones support the body, protect organs, and aid in movement, as well as their roles in mineral storage and blood cell production.