Ch. 6: Bone Tissue

Examples of flat bones

scapula, cranial bones (except temporal), sternum, pelvis, ribs

Osteoclasts are used as target cells in ________

osteoporosis

Epiphyseal plate histology

(superior to inferior) 1. Zone of calcified cartilage 2. Zone of hypertrophic cartilage 3. Zone of proliferating cartilage 4. Zone of resting cartilage

Periosteum

- attachment point for ligaments and tendons on long bones - lines medullary cavity externally - contains blood vessels and takes nutrients to osteocytes

Osteoblasts characteristics

- bone Building cells (blast for building) - synthesize and secrete collagen fibers (secrete extracellular matrix) - transform into osteocytes after being trapped by calcification

Osteoprogenitor cells characteristics

- bone stem cells (originate from mesenchymal cells that form most of conn. tissue) - only bone cell that undergoes cell division - become osteoblasts

Two types of bone formation and basic definitions

- both involve replacement of pre-existing connective tissue with bone 1. Intramembranous ossification - bone forms directly within condensed mesenchyme - arranged in sheetlike layers that resemble membranes 2. Endochondral ossification - bone forms within hyaline cartilage that develops from mesenchyme

Mineral storage and release

- calcium (99% in bone) - phosphorus - contribute to bone strength - when needed, minerals are pulled from bone tissue into bloodstream and get distributed

Mineral salts present in ECM of bone tissue

- calcium phosphate (most abundant) - ^ + calcium hydroxide = hydroxyapatite (crystals)

Histology of Bone Tissue

- cells are surrounded by abundant extracellular matrix - 15% water - 30% collagen fibers - 55% crystalized mineral salts

How do applied stresses relate to compact bone tissue?

- compact bone tissue tends to be thickest in parts of bone where stresses are applied - lines of stress can change as a result of strenuous activities

Blood cell production (hemopoiesis/hematopoiesis)

- connective tissue (red bone marrow) produces red blood cells, white blood cells, platelets

Trabeculae of spongy bone characteristics

- form network of spiky bones that gives bone structure and makes it weigh less - important for epiphysis of long bones - organized along stress lines

Development of primary ossification center (E.O.) in detail

- forms from outside inward 1. nutrient artery enters perichondrium and calcifying cartilage through the neural foramen (hole) 2. stimulates osteoprogenitor cells in perichondrium to differentiate into osteoblasts 3. perichondrium starts to form bone -> periosteum 4. (mid-region) periosteum capillaries grow into disintegrating calcified cartilage inducing growth of center 5. osteoblasts deposit bone ECM over calcified cartilage making spongy bone trabeculae 6. primary oss. center spreads from center to both ends of cartilage model (now inside out)

Development of periosteum (I.O.) in detail

- from mesenchyme present on outer spongy bone (thin outermost layer) - transformation of outer spongy bone into thin compact bone on both sides

What is an osteon? Describe main structural components.

- functional unit of compact bone - has concentric lamellae arranged around a central canal that contains a small network of blood vessels and nerves

Sulcus: definition and example

- furrow along bone surface that accommodates a blood vessel, nerve, or tendon - intertubercular sulcus of the humerus (passageway for long head of biceps brachii tendon) - on top of bone

appositional/exogenous growth

- growth from outer surface - increases thickness - deposition of extracellular matrix to periphery

interstitial/endogenous growth of cartilage

- growth from within - increases length - chondrocytes divide and secrete new matrix

Osteoclasts characteristics

- huge cell derived from fusion of monocytes - has several nuclei - concentrated in endosteum - ruffled border (enzymes dissolve ECM) - bone resorption - helps regulate blood calcium level in response to certain hormones

Articular cartilage

- hyaline cartilage covering ends of long bones where they articulate - contains no blood vessels so is affected by wear and tear; harder to repair damage

Formation of articular cartilage and epiphyseal plate (E.O.) in detail

- hyaline cartilage present in outer epiphysis and in-between epiphysis and diaphysis 1. outer cartilage transforms into articular cartilage 2. cartilage between epiphysis and diaphysis forms epiphyseal plate

Chondroblasts characteristics

- immature cartilage cells - found near perichondrium - produce components of extracellular matrix - involved in appositional growth of cartilage

function of ruffled border in osteoclasts

- increases surface area - faces inner part of bone in contact w/ ECM - releases powerful lysosomal enzymes and acids that digest protein and mineral components of extracellular matrix

Osteoprogenitor cell location

- inner portion of periosteum - endosteum - canals of bone that contain blood vessels

Medullary cavity

- inside shaft of long bones (diaphysis) - contains yellow bone marrow

Condyle: definition and example

- large, round protuberance with a smooth articular surface (to avoid friction when articulating) at the end of a bone - lateral condyle of the femur; occipital condyle (rests on top of first vertebra)

Endosteum

- lines medullary cavity of long bones internally

Line: definition and example

- long, narrow ridge or border (less prominent than crest) - linea aspera of femur (attaches adductors)

Osteocytes characteristics

- mature bone cells - main cells in bone tissue - maintain daily metabolism (exchange of nutrients and wastes with the blood) - do not undergo cell division

Chondrocytes characteristics

- mature cartilage cells - secrete and are embedded within extracellular matrix - maintain and nourish cartilage - involved in interstitial growth of cartilage

Assistance in movement

- muscles contract - pull of bone to produce movement by tendons

Fissure: definition and example

- narrow slit between adjacent parts of bones where blood vessels or nerves pass - superior/inferior orbital fissures of the sphenoid bone; carotid canal

Function of collagen fibers secreted from osteoblasts

- needed to build ECM of bone tissue - initiates calcification

Spongy bone differs from compact bone...

- not organized into osteons - no functional units - no central canals (have many thin spaces = spongy)

Foramen: definition and example

- opening where blood vessels, nerves, or ligaments pass - optic foramen (canal) of the sphenoid bone (optic nerve passes through); foramen ovale; foramen spinosum

Main components of compact bone

- osteon - lamellae - osteonic canal - canaliculi - lacunae

Orientation of osteons and purpose?

- osteons are aligned in the same direction and are parallel to length of diaphysis - shaft of long bone is able to resist bending and fracturing when considerable force is applied from either end of the bone

Development of medullary cavity (E.O.) in detail

- primary oss. center grows to ends of bone inside up 1. osteoclasts will start to breakdown some of newly formed spongy bone trabeculae and forms a cavity 2. cavity forms inside diaphysis - most of diaphysis wall will be replaced by compact bone

What are bone surface markings (processes for connective tissues)? Name all seven.

- projections or outgrowths on bone that form attachment points for connective tissue, like ligaments and tendons 1. Crest 2. Epicondyle 3. Line 4. Spinous process 5. Trochanter 6. Tubercle 7. Tuberosity

What are bone surface markings (processes that form joints)? Name all three.

- projections or outgrowths on bone that form joints 1. Condyle 2. Facet 3. Head

Crest: definition and example

- prominent ridge or elongated projection - iliac crest of hip bone

Functions of compact bone

- protection - support - resist stresses produced by movement and weight

Protection

- protects internal organs - cranial bones=brain - vertebrae=spinal cord - rib cage=heart and lungs

Advantages of communication through canaliculi

- provides many routes for nutrients and O2 to reach osteocyte - removal of waste from blood vessels located in central canal

Epiphysis

- proximal and distal ends of a long bone - contains spongy bone - contains articular cartilage

Red bone marrow during development and in newborns

- red bone marrow becomes yellow with development - all bone marrow in newborns is red and involved in hemopoiesis

Tuberosity: definition and example

- variable sized projection with rough, bumpy surface - ischial tuberosity of hip bone (absorbs weight when sitting; near ischial bursa)

Tubercle: definition and example

- variable sized rounded projection - greater tubercle of humerus (attaches muscles of rotator cuff)

Trochanter: definition and example

- very large projection - greater trochanter of femur

Six main steps of Endochondral ossification

1. Development of cartilage model 2. Growth of cartilage model 3. Development of primary ossification center 4. Development of the medullary cavity 5. Development of secondary ossification centers 6. Formation of articular cartilage and epiphyseal plate

Four main steps of Intramembranous ossification

1. Development of ossification center 2. Calcification 3. Formation of trabeculae 4. Development of periosteum

Formation of trabeculae (I.O.) in detail

1. ECM develops into trabeculae that fuse to form spongy bone around network of blood vessels 2. mesenchyme associated with blood vessels will differentiate into red bone marrow

Ossification occurs in which four principal situations?

1. Embryo and fetus- initial bone formation 2. Infancy, childhood, adolescence- bone growth until adult 3. Remodeling of bone- replacing old for new throughout life 4. Repair fractures throughout life

Types of Bones with short descriptions

1. Long- larger length than width 2. Short- cube shaped; equal width, depth, and length 3. Flat- for protection; provide extensive areas for muscle attachment 4. Irregular- don't have a specific shape 5. Sesamoid- increases mechanical advantage of knee joint 6. Pneumatized- bones with pockets 7. Sutural- between structures

Types of cells in bone tissue

1. Osteoprogenitor cells 2. Osteoblasts 3. Osteocytes 4. Osteoclasts

Functions of Bone and Skeletal System

1. Support 2. Protection 3. Assistance in movement 4. Mineral storage and release 5. Blood cell production 6. Triglyceride storage

Growth of cartilage model (E.O.) in detail

1. chondroblasts become deeply buried in cartilage ECM and mature into chondrocytes 2. chondrocytes go through cell division (interstitial growth) 3. continuous secretion of cartilage ECM increase length of cartilage model (interstitial/endogenous growth) 4. perichondrium has chondroblasts -> ECM is added on surface of models -> thickness (appositional/exogenous growth) 5. chondrocytes in mid region increase in size 6. surrounding cartilage matrix calcifies 7. other chondrocytes die because nutrients can't diffuse quick enough through ECM -> makes space = lacunae

Third step of bone growth in thickness

1. endosteum continues to encircle blood vessel 2. osteoblasts continue building concentric lamellae inward toward center of tunnel, forming a new osteon

How does the zone of calcified cartilage become new diaphysis?

1. extracellular matrix deposited between columns of lacunae calcify -> kills chondrocytes 2. osteoclasts dissolve calcified cartilage 3. osteoblasts and capillaries from diaphysis will lay down bone ECM (replacing calcified cartilage) -> endochondral ossification 4. zone becomes new diaphysis and is firmly cemented to the rest of the diaphysis of the bone

Development of cartilage model (E.O.) in detail

1. in diaphysis, mesenchymal cells will relieve chemical messengers making them crowd together in general shape of future bone 2. mesenchymal cells develop into chondroblasts 3. chondroblasts secrete cartilage ECM producing cartilage model (present in future diaphysis consisting of hyaline cartilage) 4. perichondrium wraps around cartilage model (made of mesenchyme)

Development of secondary ossification centers (E.O.) in detail

1. nutrient artery branches out into sec. oss. center 2. epiphyseal artery enters epiphysis and starts process - bone formation similar to primary oss. center except spongy bone will remain in the interior of epiphysis (no formation of medullary cavity) 3. ossification proceeds outwards from center of epiphysis to outer surface of bone

Fourth step of bone growth in thickness

1. osteoblasts continue depositing new circumferential lamellae which grows bone outward 2. deposits ECM which adds thickness 3. osteon formation repeats as periosteal ridges fold over blood vessels

First step of bone growth in thickness

1. periosteum will give rise to osteoblasts 2. osteoblasts will secrete ECM and become osteocytes 3. process forms grooves -> ridges

Second step of bone growth in thickness

1. ridges will come together where blood vessel gets entrapped in tunnel (periosteum on outside; endosteum on inside) 2. continuous secretion of ECM

Development of ossification center (I.O.) in detail

1. specific chemical messengers cause mesenchymal cells to cluster and differentiate into osteoprogenitor cells -> osteoblasts -> osteocytes 2. osteoblasts secrete ECM

What is the process of returning to homeostasis when blood calcium level is high?

1. thyroid gland releases calcitonin 2. calcitonin inhibits osteoclasts and stimulates osteoblasts 3. this stimulates calcium deposition in bones and reduces calcium uptake in kidneys 4. blood calcium level returns to normal

How many bones in an adult human body?

206

Which zone of cartilage in the epiphyseal plate is closest to the diaphysis?

zone of calcified cartilage

Which zone of cartilage anchors the epiphyseal plate to the epiphysis?

zone of resting cartilage

Support

- serves as structural framework - supports soft tissues - provides attachment points for muscle tendons

Fossa: definition and example

- shallow depression - coronoid fossa of the humerus (articulates with ulna during flexion); radial fossa; mandibular fossa - articulation of two bones

Spinous process: definition and example

- sharp, slender projection - spinous process of vertebra

What are bone surface markings (depressions and openings)? Name all five.

- sites allowing the passage of soft tissue (nerves, blood vessels, ligaments, tendons) or formation of joints 1. Fissure 2. Foramen 3. Fossa 4. Sulcus 5. Meatus

Facet: definition and example

- smooth, flat, slightly concave/convex articular surface - superior articular facet of vertebra (articulates with inferior articular facet of vertebra above)

What surrounds the body of an osteocyte and its projections?

- the body is in a small space called lacuna - small projections are in tunnels that help osteocytes communicate called canaliculi (filled with extracellular fluid)

Main components of spongy bone

- trabeculae - lamellae - lacunae - canaliculi

Meatus: definition and example

- tubelike opening - external and internal auditory meati of the temporal bone

Epicondyle: definition and example

- typically roughened projection above a condyle - lateral epicondyle of femur (attaches fibular ligament to knee joint)

Head: definition and example

- usually rounded articular projection supported on neck (constricted portion) of a bone - head of the femur (articulates with acetabulum of pelvis)

Two ways of remodeling bone

1. Bone resorption 2. Bone deposition

Metaphysis

- between diaphysis and epiphysis of long bone - where bone growth occurs

Calcification (I.O.) in detail

1. osteocytes develop extended cytoplasmic processes into canaliculi 2. calcium & mineral salts are then deposited 3. ECM hardens & calcifies

What is the process of returning to homeostasis when blood calcium level is low?

1. parathyroid glands release parathyroid hormone (PTH) 2. PTH stimulates osteoclasts 3. osteoclasts degrade bone matrix and release calcium from bones 4. this increases calcium uptake in kidneys 5. calcitriol (vitamin D) increases calcium uptake in intestines 6. blood calcium level returns to normal

______% of bodyweight is bone tissue

18-20

Which ossification process forms most bones of the body?

Endochondral ossification

Red bone marrow location

Fetus- developing bones Adults- hip bones, ribs, sternum, vertebrae, skull, epiphysis of long bones

Osteon also called

Haversian system

Which ossification process forms flat bones of the skull, most facial bones, the mandible, and the clavicle?

Intramembranous ossification

Which ossification process is generally simpler?

Intramembranous ossification

Mnemonic for irregular bones

Irregularly Shaped Teens Vape in Cars

Mnemonic to remember long bones

Long CHaRming Unicorns FulFill Time to MediTate and MediCate Patients

Mnemonic for pneumatized bones

Pneum/a->lungs->big pockets->bones with pockETs

Bone resorption

REmoval (REsorption) of minerals and collagen fibers from bone by osteoclasts

Mnemonic to remember flat bones

Sarah Could SliP wRong

Mnemonic for sesamoid bone

Sesame buns at Panera

Example of sutural bones

between the flat bones of the skull

Bone deposition

addition of minerals and collagen fibers to bone by osteoblasts

Compact bone lines surface of which bone types?

all bones

Spongy bone makes interior of which bone types?

all bones

Which bones will grow in thickness by appositional growth?

all bones

Red bone marrow components

blood cells, adipocytes, fibroblasts, macrophages, reticular fibers

Once the epiphyseal plate fades there is no more...

bone growth

Trabeculae spaces are for yellow bone marrow if...

bone produces adipose tissue

Trabeculae spaces are for red bone marrow if...

bone produces red blood cells

Ligaments attach _______ to _______

bone to bone

Components of Skeletal System

bones, cartilages, ligaments, and connective tissues

Hormones involved in calcium homeostasis

calcitonin, parathyroid hormone, calcitriol (vitamin D)

_______, ________, and ________ form an intricate and miniature system of interconnected canals throughout the bone

canaliculi; lacunae; central canals

Examples of short bones

carpals, tarsals

Epiphyseal plate closes for females (18 yrs) and males (21 yrs) when...

cartilage cells stop dividing and are all replaced by bone

Diaphysis

central shaft/ body/longest part of long bone

What is a way to detect if an individual is still growing?

check for epiphyseal line

Concentric lamellae

circular plates of mineralized extracellular matrix of increasing diameter

Examples of long bones

clavicle, humerus, radius, ulna, femur, fibula, tibia, metatarsals, metacarpals, phalanges

Where is compact bone located in long bones?

diaphysis

Epiphyseal plate develops into

epiphyseal line

What does the epiphyseal plate become in adulthood?

epiphyseal line

Example of pneumatized bones

ethmoid

Bone surface markings that are essentially holes

fissure, foramen, meatus

What does the zone of hypertrophic cartilage consist of?

large maturing chondrocytes arranged in columns

Which bones will grow in length by interstitial growth?

long bones

Tendons attach _______ to ________

muscle to bone

What type of cells align along trabeculae of new bone?

osteoblasts

When calcium levels in the blood fall below homeostasis, which bone cells act to raise calcium levels and through what mechanism?

osteoclast; resorption

Example of sesamoid bone

patella

Ossification/osteogenesis

process by which bone is formed

What is the correct order of events for bone remodeling?

resorption, deposition, osteocyte mineralization

What is the correct order in which bone reformation occurs?

resorption, reversal, matrix deposition, mineralization, resting bone

_______ + _______ = crystallize and hardens tissue = _________

salts; collagen fibers; calcification

What does the zone of proliferating cartilage consist of?

slightly larger chondrocytes stacked in rows that will undergo interstitial growth and replace cells that die further up closer to diaphysis

What does the zone of resting cartilage consist of?

small, tiny chondrocytes that do not function in bone growth

What does intramembranous ossification harden in babies?

soft spot that helps the fetus pass through the birth canal, later hardens through this type of ossification

Examples of irregular bones

sphenoid (butterfly bone), temporal bone, vertebrae, calcaneus (heel)

Osteology

study of specific bone structures and treatment of diseases having to do with the bone

Mnemonic to remember short bones

the CaT is short

If osteoclast activity exceeds osteoblast activity, how will the mass of the bone be affected?

the bone would have an decreased mineral content and, as a result. it would also be weaker.

What is the role of the epiphyseal plate in bone growth? What processes does it involve?

the growth in length of a long bone which involves: - interstitial growth - replacement of cartilage with bone by endochondral ossification on the diaphyseal side of the epiphyseal plate

Each of us will create _______ bone features that are useful for ________

unique; identification (age, gender, race, size, height, health, injuries)

Triglyceride storage

yellow bone marrow- consists mainly of adipose cells which store triglycerides (energy storage)