osseous tissue

Flashcards summarizing key vocabulary and concepts related to the integumentary system, focusing on skin, hair, and related glands.

Classification of Bones

• 206 named bones in skeleton

• Divided into two groups: Axial skeleton and appendicular skeleton

Axial skeleton

• Long axis of body

• contains The skull, vertebral column, and rib cage

Appendicular skeleton

• made up of upper and lower limbs

• Girdles attaching limbs to axial skeleton

Primary functions of bones

• Support(provides a framework for tissues and organs)

• Storage of minerals(calcium) and lipids(yellow marrow): an important reserve of calcium and phosphate ions

• Blood cell production(red marrow): blood cell formation occurs within the red marrow

• protection:axial skeleton and pelvic girdle of appendicular

• leverage(force of motion): Bones are levers, on which force can be applied and causes movement

sutural bones

• aka wormian bones found in the skull

• found in between the flat bones of the skull

long bones

• longer than they are wide

short bones

• cube-shaped bones(in wrist and ankle)

• vary in size and number in different individuals

flat bones

• thin, flat, slightly curved

• sternum, scapulae, ribs, most skull bones

irregular bones

• complicated shapes

• vertebrae, coxal bones

sesamoid bones

small, associated with tendons/muscles

bone markings

• sites of muscle, ligament, and tendon attachment on external surfaces

• joint surfaces

• conduits for blood vessels and nerves

• projections: most indicate stresses created by muscle pull or joint modifications

• depressions/openings: usually allow nerves and blood vessels to pass

sulcus

narrow grove

fossa

shallow depression

trochanter

large, rough projection

crest

prominent ridge

spine

pointed process

line

low ridge

tubercle

small, rounded projection

tuberosity

rough projection

head

expanded articular end of an epiphysis, often separated from the shaft by a narrower neck

neck

narrow connection between the epiphysis and diaphysis

facet

small, flat articular surface

condyle

smooth, rounded articular process

trochlea

smooth, grooved articular process shaped like a pulley

Gross anatomy

• Bone textures: compact and spongy bone

• compact: dese outer layer; smooth and solid

• spongy(cancellous or trabecular): Honeycomb of flat pieces(trabecular) of bone deep to compact

Diaphysis

• tubular shaft forms long axis

• compact bone surrounding medullary cavity

epiphyses

-bone ends

-external compact bone; inter spongy bone

-articular cartilage covers articular surfaces

between is epiphyseal line(remnant of childhood bone growth at epiphyseal plate)

Red marrow

the site of blood cell formation

yellow marrow

fat/adipose storage reserve

metaphases

area’region between the diaphysis and epiphysis

the periosteum cover….

the outer surfaces of bones, it consists of the outer fibrous and inner cellular layers

endosteum

• thin membrane inside the medullary cavity, has a single layer of bone-forming cells

• contains osteoblasts, osteoprogenitor cells, and osteoclasts

• is active in bone growth and repair

periosteum

• outer membrane(CT) sheath found on all bones(except at joint cavities)

• Has outer(fibrous) DICT and inner(cellular) layer

• perforating fibers(thick collage fibers) attach the periosteum to the bone beneath

• functions to protect bone, heal fractures, nourishment, and aid in tendon and ligament attachment

structure of short, irregular, and flat bones

• thin plates of spongy bone are covered by compact bones

• no shaft or epiphyses

• has bone marrow throughout spongy bone; no marrow cavity

• Hyaline cartilage covers articular surfaces

Mircoscopic anatomy of Bone: Compact bone

• Aka Lamellar bone

• Osteon or Haversian system

• Sutural unit of compact bone

• elongated cylinder parallel to long axis of bone

• composed of lamellae(each ring of an osteon)

• collagen fibers in each ring run in different directions(this gives the unit added strength)

• Osteocytes surround the central canal

canals

central(Haversian) canal runs through the core of the osteon(contains blood vessels and nerve fibers)

canaliculi

• hairlike canals that connect lacunae to each other and central canal

• allow comunicaton

• permit nutrients and wastes to be relayed from one osteon to another throughout osteon

perforating(volkmann’s) canals

• canals that lines with the endosteum at the right angle to the central canal

• connect blood vessels and nerves of periosteum, medullary cavity, and central canal i

interstitial lamellae

• incomplete lamella not part of complete osteon

• fill gaps between forming osteons

• remnants of osteons cut by bone remodeling

circumferential lamella

• just deep to periosteum

• extend around the entire surface of diaphysis

• resist twisting of long bone

spongy bone

-appears poorly organized

-trabeculae

• align along lines of stress to help resist it

• no osteons

• contain irregularly arranged lamellae and osteocytes interconnected by the canaliculi

• Capillaries in endosperm that supply nutrients

• red marrow is found in-between trabecular

cells of bone tissue

-five major cell types

-each specialized form of same basic cell types

• osteogenic cells

• osteoblasts

• osteocytes

• bone lining cells

• osteoclasts

osteogenic cells

• also called osteoprogenitor cells

• unspecialized bone stem cells derived from mesenchyme

• only bone cells go through mitosis

• mitotically active cells are found in the endosperm

• Differentiates into osteoblasts

Osteoblasts

-bone-forming cells

-synthesize and secrete unmineralized bone matrix(aka osteoid)

• includes collagen and calcium-binding proteins

• osteoblasts become trapped in their secretion(in lacunae) and then become osteocytes

Osteocytes

-mature bone cells in lacunae

-monitors and maintains bone matrix(daily metabolic activities)

-Acts as stress or strain sensors

• responds to and communicates mechanical stimuli to osteoblasts and osteoclasts, so bone remodeling can occur

osteoclasts

-derived from hematopoietic stem cells that become macrophages

-giant, multinucleate cells for bone resorption

-when active, rest in resorption bay and have a ruffled border

• ruffled border increases surface area for enzyme degradation of bone and seals off the area from the surrounding matrix

• resorption is the term for the breakdown of bone matrix, it is part of the normal development, maintenance, and growth

Bone matrix:minerals

• two thirds of bone matrix is calcium phosphate

• reacts with calcium hydroxide

• to form crystals of hydroxyapatite

• which incorporates other calcium salts and ions

matrix proteins

-one-third of bone matrix is protein fibers(collage)

process of bone remodeling

the adult skin: maintains itself, replaces mineral reserves, recycles mineral reserves, renews bone matrix, all 3 cells types are involved

bones continually…

remodel, recycles and replaces

Turnover rate varies

• if deposition is greater than removal, bones get stronger

• if removal is faster than replacement, bones get weaker

effects of exercise on bone

• minerał recycling allows bones to adopt to stress

• heavily stressed bones become thicker and stronger

bone degeneration

• bones degenerates quickly

• up to one-third of bone mass can be lost in a few weeks of inactivity

appositiona; growth vs interstitial growth

Appositional growth:thickens

Interstitial growth: lengthens

bone development

human bones grow untill about age 25

osteogenesis

bone formation

ossification

the process of replacing other tissues with bone

calcification

• the process of depositing calcium salts

• occurs during bone ossification and in other tissues

two main forms of ossification

1. endochondrial ossification

2. intramembranous ossification

endochondral ossification

• ossifies bones that originate as hyaline cartilage

• most bones originate as hyaline cartilage

intramembranouss ossification

-also called dermal ossification

• because it occurs in the dermis

• produces dermal bones such as the mandible(lower jaw) and clavicle(collarbone)

Blood supply of mature bones

1. nutrient artery and vein: a single pair of large blood vessels, enter the diaphysis through the nutrient foramen, femur has more than one pair

2. metaphysical vessels: supply the epiphyseal cartilage, where bone growth occurs

3. periosteal vessels: blood to the superficial osteon, secondary ossification center

exercise, hormones, nutrition

-normal bone growth and maintenance which depends on nutritional and hormone factors

• the hormone calcitriol

• made in the kidneys

• helps absorb calcium and phosphorus from digestive tract

• synthesis requires vitamin D3(cholecaiferol)

exercise, hormones, nutrition part 2

• growth hormone and thyroxine stimulate bone growth

• estrogens and androgens stimulate osteoblasts

• calcitonin and parathyroid hormone regulate calcium and phosphate levels

exercise, hormones, nutrition part 3

-vitamin c is required for collage synthesis and stimulution of osteoblast differentiation

-Vitamin A stimulates osteoblast activity

-Vitan K and B12 helps synthesize bone proteins

the skeleton

• bones store calcium and other minerals

• calcium is the most abundant mineral in the body

• calcium ions are vital to; membrane, neurons, muscle cells, especially heart cells

calcium regulation

• Calcium ions in body fluids

  • Must be closely regulated

• Homeostasis is maintained

  • By calcitonin and parathyroid hormone (PTH)

  • Which control storage, absorption, and excretion

calcitonin and parathyroid hormone control

• Calcitonin and Parathyroid Hormone Control

  • Affect:

1. Bones

• Where calcium is stored

2. Digestive tract

• Where calcium is absorbed

3. Kidneys

• Where calcium is excreted

parathyroid hormone

• Produced by parathyroid glands in neck

• Increases calcium ion levels by:

1. Stimulating osteoclasts

2. Increasing intestinal absorption of calcium

3. Decreasing calcium excretion at kidneys

calcitonin

• Secreted by C cells (parafollicular cells) in thyroid

• Decreases calcium ion levels by:

1. Inhibiting osteoclast activity

2. Increasing calcium excretion at kidneys

fractures

• cracks or breaks in bones

• caused by physical stress

fractures are repair in four steps

1. bleeding

2. cells of the endosperm and periosteum

3. osteoblasts

4. osteoblasts and osteocytes removed the fracture for up to a year

Fractures: bleeding

• Produces a clot (fracture hematoma)

• Establishes a fibrous network

• Bone cells in the area die

cells of the endosperm and periosteum

• Divide and migrate into fracture zone

• Calluses stabilize the break

  • External callus of cartilage and bone surrounds break

  • Internal callus develops in medullary cavity

Fractures:osteoblast

• Replace central cartilage of external callus with spongy bone

• Osteoblasts and osteocytes remodel the fracture for up to a year

  • Reducing bone calluses

major types of factors

• Transverse fractures

• Displaced fractures

• Compression fractures

• Spiral fractures

• Epiphyseal fractures

• Comminuted fractures

• Greenstick fracture

• Colles fracture

• Pott’s fracture

age related changes

• Bones become thinner and weaker with age

  • Osteopenia begins between ages 30 and 40

  • Women lose 8% of bone mass per decade, men 3%

• The epiphyses, vertebrae, and jaws are most affected

  • Resulting in fragile limbs

  • Reduction in height

  • Tooth loss

osteoporosis

• Severe bone loss

• Affects normal function

• Over age 45, occurs in:

  • 29% of women

  • 18% of men

hormones and bone loss

• Estrogens and androgens help maintain bone mass

• Bone loss in women accelerates after menopause

cancerous and bone loss

• Cancerous tissues release osteoclast-activating factor

  • That stimulates osteoclasts

  • And produces severe osteoporosis