Bone physiology I: cartilage and bone tissue and gross and microscopic anatomy of bones

Cartilage 

connective tissue in between bones

structure of cartilage

cartilage plate surrounded by a well vascularized dense CT membrane-perichondrium. Nutrients diffuse to chondrocytes from blood vessels in perichondrium

Skeletal Cartilage

type of connective tissue that forms the framework of the skeleton.

fetal skeleton

made of cartilage and fibrous membranes which are eventually replaced by bones.

what are the three skeletal cartilages

hyaline, elastic, and fibrocartilage

hyaline cartilage

-provides support with flexibility and resilience.

-it is the most abundant type of skeletal cartilage.

locations:

-ends of movable joints - articular cartilage.

-connecting the ribs to the sternum - costal cartilage.

-forming the skeleton of the larynx - laryngeal cartilage.

-reinforcing passageways to the respiratory system - tracheal and bronchial cartilages.

-supporting the external nose - nasal cartilages

Elastic cartilage

able to withstand repeated bending.

-found in two skeletal locations: external ear and the epiglottis.

Fibrocartilage

-highly compressible and provides for tensile strength.

-found in skeletal locations that are subjected to heavy pressure and stretch.

-pad-like cartilages of the knee - menisci.

-intervertebral disks.

Appositional cartilage growth

growth from the outside.

-chondrocytes below surrounding perichondrium secrete a new matrix against the existing cartilage.

Interstitial cartilage growth

growth from within.

-lacunae bound chondrocyte divide and secrete new matrix

Organic components of bone

responsible for bone’s flexibility and high tensile strength, has GAG, glycoproteins, collagen

what are the cell types

Osteoblast, osteocytes, osteoclasts

Osteoblasts

found in inner and outer surfaces of a bone

osteocytes

trapped by osteoid, mature bone cells, enclosed by mineralized osteoid maintain matrix-resorptive, synthetic

Osteoclasts

found in inner and outer surfaces of a bone. destroy bone, secrete proteases and acids

Proteases

destroy osteoid

Acids

dissolve bony matrix, release stored calcium and phosphates

Osteoid

organic part of matrix, secreted by osteoblast: GAG, glycoproteins, and collagen fibers

collagen fibers

responsible for bone's flexibility and high tensile strength

Hydroxyapatites

mineral salts, mostly calcium phosphates

calcium hydroxide

Responsible for hardness of bones

How are bones classified?

by shape as long, short, flat, or irregular

two types of osseous tissue

compact bone and spongy bone

compact bone

smooth and homogenous. dense and solid

spongy bone

composed of trabeculae and has much open space; space between the trabeculae is filled with marrow.

Large bones

-longer than wide

-include most bones of limbs.-

primarily compact bone but can contain spongy bone in the interior

Short bones

-include bones of the wrist and ankle.

-roughly cube-like.

-mostly spongy bone with a thin compact bone surface layer.

Flat bones

-include the sternum, ribs, and most skull bones.

-thin, flattened, and slightly curved.

-two, roughly parallel, compact bone surfaces with enclosing a layer of spongy bone.

Irregular bones

-include the vertebrae and hip bones.

-don't fit in any of the previous classes.

-mostly spongy bone enclosed by a thin layer of compact bone.

Periosteum

doubled layered membrane that lines the external bone surface.

periosteum is richly supplied with nerves and blood vessels, secured to the underlying bone by collagen fibers extending from the outer fibrous layer (Sharpey's Fibers)

·      outer fibrous layer - dense irregular connective tissue.

-inner osteogenic layer - abuts bone surfaces; osteoblasts, osteoclasts

Endosteum

a delicate connective tissue membrane lining all internal bone surfaces: trabeculae of spongy bones in marrow cavities, medullary cavities in compact bone, canals of compact bone; contains osteoblasts and osteoclasts.

Structure of short, irregular and flat bones

thin pates of periosteum covered compact bone enclosing endosteum covered spongy bone -no diaphysis or epiphyses.

-bone marrow is found between the trabeculae.

-in flat bone the inner layer is spongy bone = diploë.

Location of hematopoietic tissue in bones

found within some cavities of spongy bone in long bones and in diploë of flat bones.

Microscopic structure of compact bones

very dense, contains thorough system of canals and passageways.

-osteon (Haversian System) - structural unit of compact bone.

osteon (Haversian System)

-elongated cylinders running parallel to the long axis of the bone.

-formed groups of hollow tubes of bone matrix arranged concentrically.

-each matrix tube is called a lamella.

-collagen fibers within lamella run in a single direction, in adjacent lamella fibers run in opposite directions - withstand tensions.

-core of the osteon - Haversian canal (central canal) - contains blood vessels and nerve fibers serving cells in osteon.

-Perforating canals (Volkmann's): lie perpendicular to the long axis of bone.

-connect nerve and vascular supply of periosteum to those in the central canals and medullary cavity .

Compact bone – osteon structure

Osteocyte, canaliculi, interstitial lamellae, circumferential lamellae

Osteocyte

spider shaped mature bone cells occupy lacunae between lamellae.

canaliculi

hair-like canals between lacunae, continuous with central canal

circumferential lamellae

lamellae beneath periosteum, extend around circumference of the shaft.

interstitial lamellae

incomplete lamellae.

Spongy bone

consists of trabeculae a few cell layers thick; contain irregular lamellae and osteocytes interconnected with canaliculi; no osteons.

-trabeculae are arranged along the lines of stress.

osteogenesis

the process of bone formation

in embryos - leads to the formation of bony skeleton.

-in childhood through early adulthood - results in bone growth and increased size.

-in adulthood - remodeling and repair of bones.

Osteogenesis

formation of bony skeleton

Formation of bony skeleton: (ossification in embryo)

at 6 weeks, the skeleton of an embryo - fibrous membranes/hyaline cartilage.

-bone formation involves replacing this skeleton with bone tissue.

intramembranous ossification

a type of bone formation that occurs directly from mesenchymal tissue, without a cartilage intermediate, resulting in the flat bones of the skull, clavicles, and mandible

bone develops from a fibrous membrane.

formation of all flat bones.

-mesenchymal cells of fibrous membrane differentiate into osteoblasts, secrete osteoid.

endochondral ossification

bone develops from hyaline cartilage.

a process by which cartilage is converted into bone tissue, forming most of the bones in the human skeleton

forms other bones of the skeleton (non-flat bones).

-template is hyaline cartilage.

-begins at the primary ossification center at the center of the hyaline cartilage shaft.

All bones grow in thickness by

appositional growth

Why do carrier proteins have to be phosphorylated in active transport?

Increases the affinity for the substrate.

What happens to a carrier when a substrate binds?

Carrier undergoes conformational change.

What happens to the carrier after the change?

De-Phosphorylation of carrier follows conformational change.

How much sodium and potassium are moved in and out of a NaK pump?

3 Na
2 K

Does Sodium potassium pump actively use atp?

yes

NaK pump creates?

electrical gradient

What does NaK pump establish?

ion gradient

Synport?

2 molecules are moved in the same direction
Secondary Active
One molecule moved low to high, other molecule moves high to low
SGLT

Antiport?

Two substances move in opposite directions
Sodium Potassium Pump

Uniport

Facilitated diffusion into body cells; one substance transported

What does secondary active transport need to do

Create sodium gradient- has no direct use of ATP

Which messenger has cholesterol

Steroids

Are steroids polar or nonpolar

nonpolar

Are amines polar or nonpolar

nonpolar

Are peptides polar or nonpolar

polar

Where do prostaglandins act?

Smooth muscles, platelets, kidney and bone

What is mode of action

how chemical messengers exert effects on other cells varies- depends on chemical structure of messenger

Hormone binding receptors can...

alter membrane permeability by acting on a channel protein directs, directly activate enzyme, alter cytoskeletal shape, result in production of second messenger

What differs in epinephrine and heart cells and ADH and Kidneys if the membrane pathway is the same?

Protein that phosphorylates is different.

What initiates transcription in lipid soluble messengers?

Hormone/receptor complex binding to DNA promoter

Where is cartilage most prominent?

Areas where tensile strength and resiliency is needed

What are the two properties of cartilage

H2O (resiliency) and Collagen (strength)

Can cartilage regenerate?

Has limited opportunities

More collagen=

more exposure to stressors

What are the functions of bones?

Support, protection, movement, storage, blood cell formation

Organic components of bone tissue

Cells (osteoblasts, osteoclasts, osteocytes)
Matrix
Collagen

What are the inorganic components of bone tissue

Calcium salts

What are osteocytes

mature bone cells, enclosed by mineralized osteoid

What are osteoblasts

Builds bones (osteoids)

Diaphysis

shaft of lone bone

epiphyses

ends of long bone

epiphyseal line

remnant of epiphyseal plate

2 parts of periosteum (outer bone)

outer fibrous layer, inner osteogenic layer (with cells)

Endosteum (inner bone)

lining in the hollow part of a bone (cells)

What is the periosteum

double layered membrane that lines external bone surface

double layered membrane that lines external bone surface

red marrow

What type of marrow do adults have

yellow marrow

Osteons

concentric bone layers that run longitudinally alone bone

What is the function of perforating canals and central canals

help nutrients into the bone via vessels

What does the concentric lamellae do?

Make longitudinal stress easier

What do canaliculi help do?

diffuse nutrients

Where are trabeculae located

along lines of stress

are lamellae concentric

no

Properties of carrier mediated transport

specificity, competition, saturation

What is specificity

Can move ions- made to only bind to certain ions

What is saturation

limited amount of substance can be transported across a membrane by a given carrier

What is competition

Rate of "X" transport will go down when "Y" is introduced

What is neuroendocrine

Neuron messages into blood

endocrine

messenger into cell into body

Paracrine

local

Autocrine

Message into cell