Ch 2 Tissues

tissue

• collection of cells that are serving a common function isnide body

• give rise to organs

• defined by differences in

  • cellular composition

  • extracellular makeup

  • function

extracellular matrix

• contains proteins, salts, water, macromolecules, ions

• ground substance + fibers

4 primary tissue types

• epithelial tissue

• connective tissue

• nervous tissue

• muscle tissue

epithelial tissue functions

• physical protection

  • from water, chemicals, physical injury

• selective permeability

  • create lining on surface of organ or lumen

• secretion and absorption

  • small intestinal lining brings simple molecules into bloodstream

• sensation

  • epithelial skin have specialized touch receptors

lumen

• space within organ

duct cells

• create secretion

• composed in cell and released to tissue surface

• ex. sweat and saliva

general characteristics of epithalia

1. cellularity

2. polarity

3. attachment

4. avascularity

5. regenerative capacity

cellularity of epithelia

• high cell density, low EC matrix

polarity of epithelia

• anatomy oriented to apical or basolateral side

• ex. protective features on apical side, nutrient absorption on basolateral side

attachment of epithelial tissue

• connective tissue on one side with basement membrane

avascularity of epithelial tissue

• rely only on connective tissue for nutrients and waste disposal

regenerative capacity of epithelial tissue

• face lots of abrasion with short life spans

• can regenerate quickly, keratinize and rise in skin over time

exchange epithelia

• one cell layer of flattened cells

  • squamous layer with gaps

• permit rapid exchange of materials between 2 compartments

• easy passage of most molecules with simple PARACELLULAR diffusion

• ex. alveoli

functional types of epithelia

• exchange

• transporting

• ciliated

• protective

• secretory

transporting epithelia

• permit rapid exchange of materials between 2 compartments

• lines small intestine, kidney, exocrine glands

• TRANSCELLULAR movement

  • prevent free movement between adjacent cells

• substances pass through epithelial cell and cross membrane

• has specific transport proteins to maintain selective permeability

ciliated epithelia

• promote movement of extracellular particles

• lines airways

• ex. trachea moves food away from lung, ovarian tube moved egg to uterus

cilia

• microscopic folds of membrane

• sweep substances towards exit

kartagener’s syndrome

• primary ciliary dyskinesia

  • immobile/abnormal movement of cilia

• improper clearing of mucus from respiratory system → chronic colds, sinus infections → pulmonary disease

• symptom of sitis inversus

sitis inversus

• reverse organ position

• caused by kartagener’s syndrome

• due to cilia being involved in organ placement during fetal development

secretory epithlia

• organized into glands

• can be endocrine vs exocrine glands

endocrine glands

• release their secretions into blood or interstitial fluid

• made of secretory epithelia

• no duct structures

• ex. thyroid

exocrine glands

• release their secretions into ducts

• made of secretory epithelia

• secretion travels onto surface of neighboring epithelia → more localized effect

• ex. sweat gland, salivary gland

structural classifications of glands

• simple tubular

• simple alveolar

• compound tubular

• compound alveolar

• compound tubuloalveolar

examples of simple tubular glands

• intestinal glands

• gastric glands

simple alveolar gland examples

• sebaceous glands

compound tubular gland exmaples

• mucous glands in mouth

compound alveolar gland examples

• mammary glands

compound tubuloalveolar glands

• salivary glands

functional classifications of glands

• merocrine

• apocrine

• holocrine

merocrine glands

• most common functional glands

• most common

• ex. salivary glands

• secretory vesicle merges with membrane from inside cell → exocytosis releases secretion outside

apocrine gland

• secretion leaves gland in pinches off apex portion of cell

  • contains cytosol + secretion → more nutrients

• ex. mammary glands

holocrine gland

• entire cell ruptures via apoptosis → secretes all cell contents

• high mitotic division rates because to continue secretions need to make entire new cell

• very nutrient rich

• ex. sebaceous glands

  • ex. oil → bacteria feast on oil → bacteria create waste → acne/clogged ducts

intercellular junctions

• how epithelial cells are bound to each other on lateral surfaces

• types:

  • tight junctions

  • adhering junctions

  • desmosomes

  • gap junctions

tight junctions

• found along membranes of interconnected epithelia

• restrict paracellular movement

• water tight seal

  • use proteins rather than cytoskeleton

paracellular movement

• movement between epithelial cells

transcellular movement

• movement through epithelial cells

adherens junctions

• found along membranes of interconnected epithelia and basal membrane

• attach to cytoskeleton

  • actin protein goes through membrane and attaches to internal cytoskeleton of adjacent cell

• encircling of adjacent cells

• NOT WATER TIGHT

desmosomes

• found along membranes of interconnected epithelia in patches

  • abundant in basement membrane

• physical connection between adjacent cells

• patches of glycoproteins on inner surface of cell membrane

  • adhesion molecule kedherin embedded in pathc → projects through cell membrane to link with ketherin of adjacent cells

• most flexible and supportive intercellular junction

pemphigus vulgaris

• characterized by separation of epidermal layers and blistering

• autoimmune disorder

  • antibodies target desmosomes in skin/epidermis → separation of epidermal layers

gap junctions

• found along membranes of interconnected epithelia

• electrochemical connection between adjacent cells

• facilitate movement of ions and small molecules between adjacent cytoplasm

  • create passageway for electric/metabolic cell coupling

transitional epithelia

• epithelia that stretches or grows

• ex. bladder

cystic fibrosis

• caused by mutation in cytic fibrosis transmembrane receptor

• CTFR channel embedded in mucus membrane

  • usually moves chloride outside cell and sodium inside cell

• mutant CTFR channel → doesnt move chloride ions outside cell and sodium inside → water follows sodium → mucus gets thick outside cell → clogs lumens

connective tissue

• most diverse and abundant tissue type

• connects other tissues together

• usually originate from mesenchyme

characteristics of connective tissue

• low cellularity

• protein fibers

  • collagen, elastin

• ground substance

  • gel-like fluid between cells, water, ions

collagen

• ropes around ropes with some flexibility

elastin

• stretchy and elastic

extracellular matrix

• protein fibers + ground substance in connective tissue

general functions of connective tissue

• physical protection

  • cushioning

• support and structure

• storage

  • ex. bone for calcium

• binding of structures

  • to epithelia

• transport

  • ex. fluids like blood/lymph

• immune protection

  • ex. immune cells

types of connective tissue proper

• loose connective tissue

• dense connective tissue

types of supporting connective tissue

• cartilage

• bone

types of fluid connective tissue

• blood

• lymph

loose connective tissue

• fewer fibers, more ground substance

• type of connective tissue proper

1. areolar

2. adipose

3. reticular

dense connective tissue

• more fibers, less ground substance

• type of connective tissue proper

1. regular

2. irregular

3. elastic

cartilage

• semisolid matrix

• type of supporting connective tissue

1. hyaline

2. fibrocartilage

3. elastic

bone

• solid matrix

• type of supporting connective tissue

1. compact

2. spongy

areolar tissue

• type of loose connective tissue

• loosely packed assembly of all fiber types, fibroblasts, and immune cells

• primary function is to cushion organs

• contains key mediators of immunity

  • macrophages minimizes invasions of pathogens

• located under epithelial layers and surrounding organs

  • provides nutrients to epithelia

adipose tissue

• type of loose connective tissue

• matrix crowded by tightly packed adipocytes

• insulates and protects organs, stores lipids

• located around almost all organs and deepest layer of skin

reticular tissue

• type of loose connective tissue

• meshwork of reticular fibers loosely organized for flexibility

• supports tissue and immune cells of few organs

• located in lymph nodes, bone marrow, and splenic pulp

regular dense connective tissue

• fibroblasts embedded within regularly ordered assembly of collagen fibers

  • PARALLEL COLLAGEN

• resists stress of being pulled in given direction

• high strength, low flexibility

• located in tendons and ligaments

irregular dense connective tissue

• irregularly arranged collagen fibers with fibroblasts embedded within

• irregular organization provides tissue ability to resist forces in many directions

• multi-directionally strong, more flexible

• located in dermis, joint capsules, underneath epithelial linings

  • ex. under GI tract epithelia

blood

• type of fluid connective tissue

• water matrix with suspended colloid

• contains platelets, RBCs, WBCs, and neutrophils

lymph

• type of fluid connective tissue

• made from blood

• transports nutrients and waste

• provides immune system protection via surveillance and delivery of WBC to other tissues

compact/cortical bone

• absorbs great deal of mechanical energy before fracture

• organized in osteon haversion system

trabecular/spongy/cancellous bone

• can be deformed without fracture

• looser structure

osteon haversion system

• a system of tubes within tubes

• highly vascular

periosteum

• outer fibrous connective tissue around bone

• active cell activity where blood vessels originate

lamellae

• concentric layers of bone tissues surrounding central canal

• composed of salts

  • NO CELLS

lacunae

• small spaces within lamellae where osteocytes live and grow

central canal

• has blood vessels running along bone

• middle of osteon

canaliculi

• pass oxygen and CO2 between blood in central canal and osteocytes

perforating fibers

• connect blood vessels between adjacent osteons

hydroxyapatite

• mineral that most of calcium in body exists as

• the calcium and phosphate reservoir within bones

osteoprogenitors

• compact bone stem cells

• produce osteoblasts

osteoblasts

• compact bone builder cells

• secrete bony matrix

• made from osteoprogenitors

• become osteocytes

osteocytes

• mature compact bone cells

• made from osteoblasts

osteoclasts

• compact bone recycler cells

• come from different origin than osteoprogenitors/osteoblasts/osteoclasts

maturation of osteoblasts to osteocytes

• live at cell border near periosteum

• osteoblasts create bony matrix → matrix surrounds osteoblast → creates lacunae → lacunae solidifies → osteoblast becomes osteocyte

compact bone cell types

1. osteoprogenitors

2. osteoblasts

3. osteocytes

4. osteoclasts

osteoclasts

• reside at edges of compact bone

• break down bony matrix for calcium → release Ca into bloodstream

  • aka resorption

cartilage

• found throughout entire body

• semirigid connective tissue

  • not as strong as bone, but more flexible

• AVASCULAR

  • limited repair capacity → doesn’t regrow quickly

types of cartilage

• hyaline

• fibrocartilage

• elastic

chondroblasts

• begin to produce ECM

• immature cartilage cells

chondrocytes

• cells that continue to produce matrix and become surrounded by the matrix

• come from chondroblasts

chondroclasts

• breakdown cartilage

hyaline cartilage

• flexible, firm gel matrix secreted by chondroblasts → embedded in lacunae

  • 2 lacunae together

• cushions, supports, reinforces tissues and organs

  • very flexible

• located in nose, trachea, ribs, end of long bones, embryonic skeleton

fibrocartilage

• firm hyaline matrix but with more organized collagen fibers

• capable of resisting compressive force

  • shock absorption

  • less flexible

• located in components of joints with limited flexibility

  • ex. intervertebral discs, menisci, pubic symphysis

elastic cartilage

• organized same as hyaline cartilage, enriched with elastin fibers

• greater degree of flexibility and stretch

  • allows tissue to return to original shape

• no collagen fibers

• located in outer ear and epiglottis

models of cartilage growth

• interstitial growth

• appositional growth

interstitial growth

• model of cartilage growth

  • growth from within

• begins with mature cells

1. chondrocytes in lacunae undergo mitosis → 2 chondrocytes occupy 1 lacuna

2. cells synthesize and secrete own ECM → separated from each other by matrix border

3. results in 2 chondrocytes, 2 lacuna, more ECM secretion

appositional growth

• model of cartilage growth

• growth in length

• begins with stem cells

1. stem cells along internal edge of perichondrium begin to divide into chrondroblasts

2. chondroblasts begin to produce ECM → differentiate into chondrocytes → form new lacunae

cauliflower ear

• injury in ear → impaired blood flow → overgrowth of fibrocartilage

endochondral ossification

• model of bone growth

• bones coming from cartilage in fetus

  • cartilage models of bones

• cartilage model formation → hypertrophy and calcification → primary ossification center → perichondrium into periosteum → medullary cavity formation → secondary ossification center

epiphyseal plate

• cartilage between diaphysis and epiphysis

• remains during endochondral ossification

fibrodysplasia ossificans progressiva

• injured muscle tissues and connective tissue replaced by bone

• mutation to gene → receptor turned on

metaplasia

• one tissue type replaced by another

• ex. barrets esophagus, barrets adenocarcinoma

barrets esophagua

• metaplasia disorder

• replace esophagus stratified squamous epithelia with stomach simple columnar secretory mucus membrane → chronic acid reflux

barretts adenocarcinoma

• ciliated trachea epithelia replaced by stratified squamous epithelia of skin

• lose cilia sweeping out debris → problem compounded → smokers cough

hypertrophy

• cell growth in absence of division

• ex. cardiac hypertrophy

  • thick heart walls → difficult circulation

hyperplasia

• tissue growth due to normal cell growth

  • cells multiply faster than normal but have no different characteristics

• ex. benign prostatic hyperplasia

neoplasia

• tissue growth due to uncontrolled abnormal cell growth

• neoplasm = tumor