A&P Chapter 6

Hyaline cartilage covers the ends of long bones as articular cartilage, providing springy pads that absorb compression at joints.

Hyaline cartilage is found on the ends of bones that form movable joints, where it is referred to as articular cartilage.

Interstitial growth occurs when chondrocytes divide and form new matrix, thereby expanding the cartilage tissue from within. (Note: the word inter means between, and stitial means space; these are common roots for anatomical terms.)

This is false; long bones include all limb bones except the patella, tarsals and carpals.

The main role of the appendicular skeleton involves locomotion; it also allows us to manipulate our environment. The axial skeleton is mostly involved in supporting other body parts and protecting vital organs.

Red bone marrow found within certain regions of spongy bone is the site of blood cell formation from the differentiation of hematopoietic stem cells.

Glycogen production (glycogenesis) is not a role of bone; it takes place primarily in muscle and liver cells.

Bone is a reservoir for calcium and phosphate.

The external membrane of bone, the perisosteum, includes a fibrous outer layer composed of dense irregular connective tissue.

The articular cartilage at the ends of long bones is formed from hyaline cartilage.

The shaft of an adult long bone is composed of compact bone.

Yellow bone marrow within the medullary cavity is composed primarily of adipose tissue (fat).

Hematopoietic tissue is found in the spaces within the red bone marrow found within certain body locations consisting of spongy bone. Examples include the diploe of flat bones and the proximal epiphyses of the femur and humerus (pictured).

Lamellae are layers of bony matrix synthesized by osteoblasts during bone growth and maintenance.

A Haversian (or central) canal runs lengthwise at the center of each osteon.

Cytoplasmic extensions of osteocytes form contacts within hairlike canals, termed canaliculi, within the lamellae. Сanaliculi allow for communication and exchange of materials between osteocytes.

Calcium is an inorganic component of the bone matrix and is deposited from the interstitial fluids. The organic osteoid secreted by bone-forming cells is composed of proteoglycans, glycoproteins, and collagen.

The honeycomb-like network of spongy bone is constructed of bony plates called trebeculae.

Osteoblasts are the bone-forming cells that produce the organic bone matrix, the osteoid. Mature bone is produced once the inorganic matrix forms around the cells and collagen fibers of the organic matrix.

The structural unit of compact bone is the osteon, an elongated cylinder oriented parallel to the long axis of the bone.

A trochanter is a bone projection. All of the other choices listed are categorized as depressions or openings.

In adults, much of the yellow marrow is located in the medullary cavity of the long bones.

Osteoclasts are derived from the same hematopoietic stem cells that differentiate into macrophages; they are not derived from osteogenic cells.

In infants, but not adults, red marrow (hematopoietic tissue) is found in the medullary cavity of long bones.

The osteon, also called the Haversian system, is the structural unit of compact bone.

The exceptional hardness of bone, which allows it to resist compression, is attributed to the presence of mineral salts called hydroxyapatites. The hydroxyapatites, mainly calcium phosphates, form the inorganic matrix of bone.

Long bones elongate from growth at the epiphyseal plate, a layer of hyaline cartilage between the epiphyses and diaphysis of long bones.

Flat bones consist of two thin plates of compact bone enclosing a diploë (spongy bone layer).

The figure illustrates the formation of new bones within a fibrous membrane ("intramembranous") during embryonic development.

Mesenchymal cells are stem cells that differentiate into the matrix-forming cells of the various connective tissues, including the osteoblasts that form bone.

The figure illustrates a step in the embryonic formation of a bone from a cartilage model.

The figure illustrates a step in the embryonic formation of a bone from a cartilage model.

The cartilage models used to form bones are composed of hyaline cartilage. This tissue persists within the epiphyseal plate at the boundary between primary and secondary ossification centers.

The expansion of the matrix results in the pushing of the epiphysis away from the diaphysis. This leads to the lengthening of the bone by interstitial growth.

Calcification of the cartilage matrix leads to its deterioration and replacement by bone.

Growth in width involves the adding of layers of lamellar (compact) bone along the bone's outer surface. This process of growth by "layering" is termed appositional growth and is distinct from growth by expansion of the interior matrix (interstitial growth).

As the bone widens, the matrix at the endosteal surface is resorbed to maintain the proper thickness of the walls surrounding the medullary cavity.

Endochondral ossification is the formation of bone from hyaline cartilage models. The hyaline cartilage must be broken down and replaced with the bone tissue.

During infancy and childhood the single most important stimulus for bone growth is growth hormone. It directly stimulates growth of the hyaline cartilage that forms the epiphyseal plates in long bones, causing the bones to lengthen.

Parathyroid hormone functions to stimulate the activity of osteoclasts in bone tissue.

In order, here are the stages of bone fracture healing: (1) formation of a hematoma, (2) formation of a fibrocartilaginous callus, (3) formation of a bony callus, and (4) bone remodeling.

Glucagon's main action is to increase blood glucose levels by triggering the breakdown of glycogen in the liver; it does not affect bone remodeling.

In a compound (open) fracture the fractured bone ends penetrate the skin. Such open injuries carry a higher risk of infection.

From start to finish, a fracture is repaired by: (1) formation of a hematoma, (2) formation of a fibrocartilaginous callus, (3) formation of a bony callus, and (4) bone remodeling. Use the pneumonic HFBR (His Femur Better Repair!) to help you remember the order. H = hematoma, F = fibrocartilaginous callus, B = bony callus, R = remodeling.

Osteoporosis refers to groups of diseases in which bone resorption outpaces bone deposit. The bones become fragile and easily fractured. The composition of the matrix remains normal, but bone mass declines, and the bones become porous and light.

Correct, Paget's disease is associated with excessive and haphazard bone deposition and resorption.

-Hyaline cartilage -elastic cartilage -fibrocartilage

Skeletal cartilage is primarily WATER. (matrix of cartilage has lots of water) -This allows it to RESIST COMPRESSION.

End of long bones

Ear and epiglottis

Intervertebral discs, pubic symphysis, meniscus

Hyaline Cartilage

Elastic Cartilage

Fibrocartilage

Skeletal cartilage have no NERVES, no BLOOD VESSELS -surrounded by PERICHONDRIUM (membrane) -Layer of 'DENSE IRREGULAR' connective tissue surrounding cartilage -Source of 'BLOOD VESSELS SUPPLYING NUTRIENTS' by diffusion to cartilage cells' (nutrients are diffused from here) FUNCTIONS: SUPPORT & PROTECTION, CUSHIONING SHOCK BETWEEN BONES, & CONNECTING TISSUES

APPOSTITIONAL GROWTH

INTERSTITIAL GROWTH

CALCIFICATION OF CARTILAGE

AXIAL SKELETON

APPENDICULAR SKELETON

LONG BONES

IRREGULAR BONES

FLAT BONES

SHORT BONES

-SUPPORT -PROTECTION -MINERAL AND GROWTH FACTOR STORAGE -HEMATOPOIESIS IN RED MARROW CAVITIES (BLOOD CELL FORMATION) -TRIGLYCERIDE (FAT) STORAGE IN BONE CAVITIES AS SOURCE OF ENERGY -HORMONE PRODUCTION OSTEOCALCIN, HELPS REGULATE INSULIN SECRETION, GLUCOSE LEVELS, AND METABOLISM -ANCHORAGE LEVERS FOR SKELETAL MUSCLE ACTION

ORGANS

-OSSEOUS TISSUE -NERVOUS -CARTILAGE FIBROUS CONNECTIVE -SMOOTH MUSCLE -EPITHELIAL CELLS IN ITS BLOOD VESSELS

COMPACT BONE; SPONGY BONE

COMPACT (LAMELLAR)

SPONGY (TRABECULAR) - INTERNAL LAYER

PLATES

ENDOSTEUM

Spongy Bone

Compact bone

OSTEOGENIC

PERIOSTEUM

DEPOSITION

DIPLOË

-Proximal epiphysis -Diaphysis (shaft) -Distal epiphysis

-found within TRABECULAR CAVITIES of SPONGY BONE of long bones and DIPLOE (flat bones) ex: sternum; called RED MARROW CAVITIES

Hematopoietic

-'ADULTS' long bones have 'LITTLE red marrow' *Only found in HEADS of FEMUR & HUMERUS* -Red marrow in diploe & some irregular bones is the MOST ACTIVE

YELLOW MARROW can convert to 'RED MARROW' if red blood cells are needed (ex: anemia)

Osteogenic cell

Osteoblast

Osteocyte

Osteoclast

ORGANIC MATTER

INORGANIC MATTER

-dry weight is 1/3 organic, 2/3 inorganic matter -combination provides for 'STRENGTH & RESILIENCE' -minerals resist compression; collagen resists tension(stretching)

A SINGLE OSTEON

LAMELLAE

CANALICULI

WITHSTAND TORSION STRESSES (TWISTING FORCE)

ARTERIES, VEINS, NERVE FIBER

PERFORATING (VOLKSMANN'S) CANALS

ENDOSTEUM

CANALICULI

INTERSTITIAL LAMELLA

-APPEARS POORLY ORGANIZED, ONLY A FEW CELLS THICK

- NO OSTEONS -TRABECULAE 'ALIGN ALONG LINES OF STRESS' TO HELP BONE 'RESIST STRESS'

LAMELLAE

OSTEOCYTES

FALSE

OSSIFICATION (OSTEOGENESIS)

INTRAMEMBRANOUS OSSIFICATION

ENDOCHONRAL OSSIFICATION

1. MESENCHYMAL CELLS CLUSTER AND BECOME OSTEOBLASTS, FORMING OSSIFICATION CENTERS 2. OSTEOID IS SECRETED, THEN CALCIFIED 3. OSTEOID IS LAID DOWN BETWEEN BLOOD VESSELS, RESULTING IN TRABECULAE CALLED WOVEN BONE - MESENCHYME CONDESES TO FROM PERIOSTEUM 4. LAMELLAR BONE REPLACES WOVEN BONE AND RED MARROW APPEARS (VIA ITS VASCULAR TISSUE)

1 BONE COLLAR FORMS AROUND THE DIAPHYSIS OF THE HYALINE CARTILAGE MODEL 2 CARTILAGE IN THE CENTER OF THE DIAPHYSIS CALCIFIES AND THEN DEVELOPS CAVITIES 3 THE PERIOSTEAL BUD (blood vessels, nerves, red marrow, osteogenic cells, and osteoclasts) INVADES THE INTERNAL CAVITIES AND SPONGY BONE 4 THE DIAPHYSIS ELONGATES AND A MEDULLARY CAVITY FORMS. SECONDARY OSSIFICATION CENTERS APPEAR IN THE EPIPHYSES 5 THE EPIPHYSES OSSIFY. WHEN COMPLETED, HYALINE CARTILAGE REMAINS ONLY IN THE EPIPHYSEAL PLATES AND ARTICULAR CARTILAGES

Osteoblasts

Epiphyseal plate

True

Appositional growth

Growth hormone

spongy bone

osteoblasts

Mechanical signals

Osteoclasts

parathyroid hormone (PTH)

negative feedback hormonal loop for Ca2+ homeostasis - controls blood Ca2+ levels Responses to mechanical stresses - including gravitational forces

WOLFF'S LAW

osteomalacia (soft bones)

rickets (osteomalacia or children)

osteoporosis

1. a hematoma forms 2. fibrocartilaginous callus forms 3. bony callus forms 4. bone remodeling occurs

osteoporosis

Paget's disease