BIOL 2401 Unit #2 Exam (Ch. 6) Osseous Tissue and Bone Structure

When calcitonin is released what two major effects does it have?

1. Osteoclast activity decreased 2. Kidneys increase secretion of calcium in the urine, & secrete less calcitriol lessening the calcium absorption in the intestines

When parathyroid hormone is released what three major effects does it have?

1. Stimulate osteoclast activity to release calcium into the blood 2. Increase absorption of calcium in the intestine 3. Increase absorption of calcium in the kidney, lower calcium loss in urine

How much calcium is in the typical human body and where is most of it deposited?

2.2-4.4 lbs of calcium, 99% stored in the skeleton

How many bones does the adult skeleton typically contain?

206 major bones

Lacunae

A pocket sandwiched between layers of bone matrix with a single osteocyte occupying the lacuna

How much of the skeleton is recycled each year in a young adult?

Almost 1/5 of the skeleton

What is the endosteum?

An incomplete cellular later that lines the medullary cavity

What is an osteon?

Basic functional unit of mature compact bone

What happens if the activity of osteoclasts exceeds the activity of osteoblasts in a bone?

Bone matrix would be broken down by osteoclasts without enough bone matrix being rebuilt by osteoblasts

What hormone is released when blood calcium concentrations rise above normal and what gland produces it?

Calcitonin from the thyroid gland

Calcitriol and vitamin D

Calcitriol is synthesized in the kidneys & essential for normal calcium & phosphate ion absorption in the digestive tract. Calcitriol is synthesized from a related steroid, cholecalciferol (vitamin D3) which can be produced in the skin or absorbed f/ the diet

What materials comprise the bone matrix?

Calcium phosphate (2/3 weight of bone) Collagen fibers (1/3 weight of bone)

What type of tissue is replaced by bone during endochondral ossification?

Cartilage

Medullary cavity

Central space within bone, marrow cavity, surrounded by compact bone

Sinus

Chambers within a bone, normally filled with air (openings)

In endochondral ossification what is the original source of osteoblasts?

Chondrocytes

What is the role of collagen in bone matrix?

Collagen fibers are flexible but tough, can easily tolerate twisting /bending but offer little resistance to compression (calcium phosphate crystals are very hard but relatively inflexible/quite brittle)

What are Sharpey's fibers?

Collagen fibers incorporated into bone tissue from tendons & ligaments, as well as from the superficial periosteum

What type of tissue is osseous tissue?

Connective tissue

Spongy bone

Consists of an open network of tabeculae within epiphses

Central canal (Haversian canal)

Contains one or more blood vessels, run parallel to the surface of the bone

Fissure

Deep furrow, cleft or slit (Openings)

What is the difference between endochondral ossification and intramembranous ossification?

Endochondral ossification: cartilage models gradually being replaced by bone Intramembranous ossification: osteoblasts differentiate within a mesenchymal or fibrous connective tissue

What is the difference in an epiphyseal plate and an epiphyseal line?

Epiphyseal plate is epiphyseal cartilage where new cartilage is still being produced Epiphyseal line is what remains after epiphyseal growth has ended. After puberty, the rate of epiphyseal cartilage production slows & the rate of osteoblast activity increases, thus the epiphyseal cartilage gets narrower until it disappears.

Sex hormones

Estrogen in females & testosterone in males stimulate osteoblasts to produce bone faster than the rate at which the epiphyseal cartilage expands, leading to epiphyseal closure

Epiphysis

Expanded area at the end of long bone

Head

Expanded articular end of a epiphysis, often separated f/ the shaft by a narrower neck (Ex: round part of bony protrusion on femur) (Projections for forming joints)

Perforating canal (Volkmann's canals)

Extend perpendicular to the surface & supply blood to osteons deeper in the bone & to tissue of the medullary cavity

Diaphysis

Extended tubular shaft of long bone

Interstitial lamellae

Fills the spaces between osteons in compact bone, are remnants of osteons whose matrix components have been almost completely recycled by osteoclasts

Circumferential lamellae

Found at the outer & inner surfaces of the bone, where they are covered by the periosteum & endosteum, produced during growth of the bone

Fracture

Fractures are named by 4 either/or categories, each w/ 2 groupings 1. position of bone ends (nondisplaced or displaced) 2. completeness of break (complete or incomplete) 3. orientation of break to the bone's long axis (linear or transverse) 4. whether bone penetrates skin (open/compound or closed/simple)

Growth hormone and thyroxine

Growth hormone is produced by the pituitary gland & thyroxine from the thyroid gland & both stimulate bone growth by stimulating protein synthesis & the rates of cell division & cell growth

What is appositional growth and how does it take place?

Growth in width, bone increases in diameter at the outer surface

Osteon

In an osteon, osteocytes are arranged in concentric layers around a vascular central canal that contains blood vessels that carry blood to and from the osteon

Osteopenia

Inadequate ossification, bones become thinner & weaker

Trochanter

Large, rough projection (projections where muscles, tendons, or ligaments attach)

Concentric lamellae

Layers of the bone matrix, each osteon forms a series of nested cylinders are the central canal

What are trabeculae?

Located in spongy bone where lamellae are not arranged in osteons, instead a matrix forms a meshwork of supporting bundles of fibers

Line

Low ridge (Projections where muscles, tendons, or ligaments attach)

Osteocyte

Mature bone cells that make up most of the cell population

What kind of tissue is replaced by bone during intramembranous ossification?

Mesenchymal or fibrous connective tissue

Neck

Narrow connection between the epiphysis & diaphysis (projection for forming joints)

Sulcus

Narrow groove (depression)

Canaliculi

Narrow passageways that radiate through the bone matrix, containing cytoplasmic extensions of osteocytes, supporting cell-to-cell communication between osteocytes in different lacunae & give access to nutrients supplied by blood vessels in the central canal

Metaphysis

Narrow zone connecting the epiphysis and diaphysis

Minerals

Normal bone growth & maintenance cannot take place w/o sources of calcium & phosphorous

Differentiate between ossification and calcification.

Ossification: bone formation (osteogenesis) 1. endochondral ossification 2. intramembraneous ossification Calcification: the deposition of calcium salts takes place during ossification, but can occur in other tissues

List the four types of bone cells and their functions.

Osteogenic cells (osteoprogenitor cells) are stem cells that divide to produce daughter cells that differentiate into osteoblasts Osteoblasts product new bone matrix (osteogenesis) or (ossification) Osteocytes are mature bone cells that make up most of the cell population, occupied within a single lacuna between layers of matrix, & cannot divide Osteoclasts are cells that absorb & remove bone matrix, large with 50 or more nuclei, usually in osteoclastic crypts

Calcitonin and parathyroid hormones

PTH from the parathyroid glands stimulate osteoclast activity, increase absorption of calcium in the intestines & kidneys to increase the blood calcium ion level Calcitonin from the thyroid gland decreases osteoclast activity, decreases the absorption of calcium in the intestines & kidneys to decrease the blood calcium ion level

What hormone is released when blood calcium concentrations fall below normal and what gland produces it?

Parathyroid hormone (PTH) from the parathyroid gland

Ramus

Part of a bone that forms an angle w/ the rest of the structure (Projections)

Meatus

Passage or channels, especially the opening of a canal (openings)

Spine

Pointed process (projections where muscles, tendons, or ligaments attach)

Process

Projection or bump (projections)

What is the difference between red bone marrow and yellow bone marrow?

Red bone marrow forms red blood cells Yellow bone marrow forms lipids (adipose tissue important as an energy reserve)

Osteoporosis

Reduction in bone mass sufficient to compromise normal function (brittle/fragile bones)

Describe the effects of exercise on bone.

Regular exercise is an important stimulus for maintaining normal bone structure. Whenever a bone is stressed, the mineral crystals generate minute electrical fields, osteoblasts are attracted to these electrical fields, & once in the area begin to produce bone

Vitamin C

Required for certain key enzymatic reactions in collagen synthesis, & stimulates osteoblast differentiation, lack of vitamin C causes loss of bone mass/strength

Tuberosity

Rough projection (projections where muscles, tendons, or ligaments attach)

Foramen

Rounded passageway for blood vessels or nerves (Ex: ) (Openings)

Fossa

Shallow depression (distal end of humerus above the condyle & trochlea) (Depressions)

Facet

Small, flat articular surface (Ex: distal end of femur flat surface on condyle) (Projections for forming joints)

Tubercle

Small, rounded projection (projections where muscles, tendons, or ligaments attach)

Trochlea

Smooth, grooved articular process shaped like a pulley (projections for forming joints)

What is the periosteum and what is its function?

Superficial layer of compact bone that covers all bones, a membrane with a fibrous outer layer & cellular inner layer It isolates the bone from surrounding tissues, provides a route for the blood vessels & nerves, & takes part in bone growth & repair

Describe five functions of the skeletal system.

Support (structural, framework for attachment of soft tissue & organs) Storage of minerals & lipids (calcium, lipids in yellow bone marrow) Blood cell production (RBC & WBC are produced in red bone marrow) Protection (protect the heart, lungs, brain, spinal cord, digestive/reproductive organs) Leverage (bones function as levers, range of movement)

What are the six categories used to classify bones based on their shapes? (Provide an example for each category.)

Sutural bones (coronal suture) Irregular bones (vertebra) Short bones (carpal & tarsal bones) Flat bones (patietal bone, sternum, ribs) Long bones (femur) Sesamoid bones (patella)

What is bone remodeling?

The process of continually recycling the organic and mineral components of the bone matrix

Compact bone

The wall of the diaphysis consists of compact bone, which is relatively dense & solid, that surrounds the medullary cavity

Describe the structure of a flat bone.

Thin, parallel surfaces (roof of skull, sternum, ribs, shoulder blades)

Vitamin A K B12

Vitamin A stimulates osteoblast activity Vitamin K & B12 are required for the synthesis of proteins in normal bone

Canal

duct or channel (Ex: skull) (openings)

Crest

prominent ridge (Ex: edge of pelvis) (Projections where muscles, tendons, or ligaments attach)

Condyle

smooth, rounded articular process (Ex: distal end of femur) (Projections for forming joints)