Chapter 6:Cartilage and Bone tissues
Skeletal System
Composed of dynamic living tissues. Interacts with all of the other organ systems. Continually rebuilds and remodels itself. Includes the bones of the skeleton as well as cartilage, ligaments, and other
connective tissues that stabilize or connect the bones. Supports our weight. Interacts with muscles to produce movements. Permits us to sit, stand, walk, and run.
3 Major Functions of Cartilage Supporting soft tissues. Providing a gliding surface at articulations (joints), where two bones meet. Providing a model for the formation of most of the bones in the body.
Types of Cartilage The human body has three types of cartilage:Hyaline Cartilage
Most abundant type Found in: trachea, larynx, articular (joint) surfaces, epiphyseal plates Flexible support with cushioning Surrounded by a connective tissue covering called a perichondrium
Fibrocartilage Extracellular matrix has numerous collagen fibers Resists stretching and compression Acts as a shock absorber, especially between vertebrae (discs), in the knee and
between the pubic bones Lacks a perichondrium
Elastic Cartilage Matrix contains highly branched elastic fibers Found in external ear (pinna) and epiglottis Located where very flexible support is needed
Growth Patterns of Cartilage
A. Interstitial growth; (growth from within)
Chondrocytes undergo mitosis Two cells are now in a single lacuna As new cells secrete matrix, they are pushed apart Now each cell is in its own lacuna; growth has
occurred
New VocabularyChondro-”cartilage”Osteo –”bone”Blast- “immature cell” often undifferentiated; usually means to make something (e.g. mitosis)
Ex. Chondroblast, osteoblastCyte- “cell”
Ex. Chondrocyte, osteocyteClast-”break down” something
Homeostasis Note-blast and –clasts are usually in equilibrium and maintain homeostasis with each other
Building (Blasts) For example building cartilage or bone
Collapse (Clasts)For example break down cartilage or bone
Growth Patterns of CartilageB. Appositional growth; (growth on the outside edge)
Stem cells inside of perichondrium divide into chondroblasts
New chondrocytes produce matrix around themselves becoming chondrocytes in a lacuna
New growth has now occurred on the outside of the cartilage
Bone tissueFunctions of Bone
Bones are composed of all tissue types. Their primary component is osseous connective
tissue. The matrix is sturdy and rigid due to calcification, or mineralization.
Support and Protection
Bones provide structural support and serve as a framework for the entire body. Bones also protect many delicate tissues and organs from injury and trauma.
Movement Muscles attached to the bones of the skeleton contract and exert a pull on the
skeleton, which then functions as a series of levers.
Hematopoiesis Blood cell production in red bone marrow, which is located in some spongy bone. Red bone marrow contains stem cells that form all of the blood cell types.
Storage of Mineral and Energy Reserves More than 90% of the body’s reserves of the minerals calcium and phosphate are
stored and released by bone. Calcium is an essential mineral for such body functions as muscle contraction,
blood clotting, and nerve impulse transmission. Phosphate is needed for ATP utilization and phospholipid production, among
other things.
Classification of Bone by ShapeLong;
- greater length than width- Posses an epiphysis (end) and diaphysis (shaft)- Found primarily in appendicular skeleton
Short- Equal length and width- Found in wrists and ankles and knee cap
Classification of Bone by ShapeFlat
- Flat, thin surface- Extensive surfaces for muscle attachment- Found in skull, shoulder blade, and chest bones
Irregular- Complex shapes- Found in vertebrae and skull
Long bone structure
Diaphysis; shaft (long part) contains medullary (marrow
cavity)Metaphysis;
area of growth between diaphysis an epiphysis, disappears after maturity (when growth stops)
Epiphysis; ends containing spongy bone
Articular cartilage; hyaline for shock absorption
Medullary (marrow) cavity; contains bone marrow
Endosteum; fibrous lining of marrow cavity that assists with bone repair after break
Periosteum; fibrous cover of bone which allows blood vessels into bone, assists with
repair, and prevents organs from damaging contact with bone
Four Types of Bone Cells
Osteoprogenitor cells stem cells derived from mesenchyme which produce other stem cells and
osteoblasts Osteoblasts
produce new bone, and once osteoblasts become entrapped in the matrix they produce and secrete, they differentiate into osteocytes
Osteocytes mature bone cells
Osteoclasts are involved in bone resorption
Flat Bones Within the Skull Composed of two layers of compact bone, with a region of spongy bone
sandwiched between them. Both layers of compact bone are covered by periosteum
Bone Ossification (synonymous with bone tissue formation) Begins in the embryo and continues as the skeleton grows during childhood and
adolescence. Even after the adult bones have formed, ossification continues. By the eighth through twelfth weeks of embryonic development, the skeleton
begins forming from either thickened condensations of mesenchyme or a hyaline cartilage model of bone.
These models are replaced by hard bone.
Intramembranous Ossification It begins when mesenchyme becomes thickened and condensed with a dense supply of blood capillaries, and continues in several steps.
Endochondral Ossification Begins with a hyaline cartilage model and produces most of the other bones of the skeleton, including the bones of the upper and lower limbs, the pelvis, the vertebrae, and the ends of the clavicle.
Epiphyseal Line FormationEndochondral ossification of a long bone occurs in progressive stages. Bone growth is complete when each epiphyseal plate has ossified and the epiphyseal line has formed.
Bone RemodelingAlthough adult bone size has been reached, the bone continues to reshape itself throughout a person’s lifetime in a constant process of bone resorption and deposition.
Bone Growth
Appositional growth occurs within the periosteum. Bone Remodeling
The continual deposition of new bone tissue and the removal (resorption) of old bone tissue.
o helps maintain calcium and phosphate levels in body fluids, and can be stimulated by stress on a bone
o occurs at both the periosteal and endosteal surfaces of a bone o
Bone remodeling after injury
Blood Supply and Innervation Bone is highly vascularized, especially in regions containing red bone marrow. Blood vessels enter bones from the periosteum. The nutrient artery and the nutrient vein supply the diaphysis of a long bone.
Effects of Hormones Control and regulate growth patterns in bone by altering the rates of both
osteoblast and osteoclast activity. Growth hormone affects bone growth by stimulating the formation of another
hormone, somatomedin which is produced by the liver. Somatomedin directly stimulates growth of cartilage in the epiphyseal plate.
Thyroid hormone stimulates bone growth. Growth hormone and thyroid hormone regulate and maintain normal activity at
the epiphyseal plates until puberty. Calcitonin inhibits osteoclast activity.