connective tissues

these flashcards go over cells+tissues lec 2-3. epithelial tissue & connective tissue. muscle & nerves will be another deck.

• covers surfaces

• lines cavities and ducts

• glands

• arranged in sheets

general features of epithelial tissue

• microfilament actin

• intermediate filament keratin

cytoskeleton structure

-claudin and occludin proteins span the gap between plasma membranes
-electrically charged seal to maintain cell polarity
-individual transmembrane sealing strands

found in KIDNEYS, STOMACH, BLADDER.

tight junctions

• cadherin protein spans gap,

• within adhesion plaque ‘belt’ CADHERIN to CATENIN.

• CATENIN links to ACTIN.

• prevent cell separation from tension like contraction.

adherens junction

• cadherin spans gap, within adhesion plaque connects to desmoplakin.

• desmoplakin link to keratin (cytoskeleton) and spans out.

• Spans from one desmosome to another on other cell.
  
  BIND muscle cells.
  found in SKIN EPITHELIUM, MUSCLE CELLS

desmosomes

• gap junction

• 6 connexins aggregate = one connexon.

• tunnel from two membranes

junction for communication

• epithelia to basement membrane.

• linker protein is integrin, binding to lamenin (protein in BM).

• integrin also connects to keratin and spans out from adhesion plaque.

hemidesmosome

• basal lamina (secreted by epithelial cells) containing collagen, laminin, proteoglycans, glycoproteins

• reticular lamina (produced by cells of underlying connective tissue, fibroblasts) containing fibrous proteins, fibronectin, collagen.

• exchange of nutrients and waste by diffusion from vessels in connective tissue (epithelium to BM).

BASEMENT MEMBRANE STRUCTURE

• supports epitheliun

• provides surface for epithelial cells to migrate for growth/wound repair

• physical barrier

• filtration of substances in kidney (glomerulus)

functions of basement membrane

• filtration (kidney, glomerulus)

• diffusion (lungs)

• secretion where smooth surface needed

• (outer layer of serous membranes = mesothelium + connective tissue)

simple squamous epithelium

mesothelium - lines pericardial (heart), pleural(guts), peritoneal (lungs)

endothelium - lines inside of heart and the blood and lymphatic vessels

simple squamous subtypes

• pancreas + kidney ducts,

• secretory chambers of thyroid,

• lens surface,

• pigment at posterior of retina
  

simple cuboidal epithelium locations

• non ciliated - goblet cells , may have microvilli ‘brushed border’.

• ciliated - goblet cells, have cilia (long)

simple columnar epithelium subtypes

• in bowmans capsule + glomerulus in kidney,

• inside eye,

• alveoli

simple squamous epithelium locations

• non ciliated - gut mucosa lining from stomach to anus, ducts of many glands, gallbladder

• ciliated - bronchiole, uterine fallopian tubes, sinuses, spinal cord, brain ventricles

simple columnar epithelium subtypes location

• cilia move substances (very long. found in respiratory tract cells e.g moving mucus)

• microvilli increase surface area for absorption nutrients go through BM. (small intestine)

simple columnar epithelium membrane mods

• only bottom layer connected to BM

• protection from trauma, stresses, microbes

• keratinised - dry trauma (skin)

• non-keratinised - wet trauma (mouth, throat, etc)

stratified squamous and subtypes

• all cells actually in contact with bm but look stacked

• ciliated - cilia on some cells, secrete mucus from goblet cells.
  found in most upper airways.

• non-ciliated - no cilia or goblet cells.
  found in larger ducts of glands, male urethra and epididymis.

pseudostratified columnar epithelium + subtypes

• cuboidal - ducts of adult sweat glands, esophageal glands, male urethra

• columnar - (same as last), plus anal mucosal membrane, conjunctiva of eye

• transitional - bladder (expand and retract when empty)

stratified epithelium locations

• secrete directly into blood via traversing intersitial fluid
  found in pituitary , pineal , thyroid , parathyroid (endocrine organs)

e.g insulin (pancreas islet cells)

endocrine gland

• directly into ducts that empty onto surface
  found in sweat and salivary glands, oil glands, wax glands, pancreas (digestion, ducts)

exocrine gland

• binds, supports, strengthens other body tissues

• a major transport system of the body (blood)

• a major site of stored energy reserves (fat or adipose connective tissue)

what is the general role of connective tissue

• secreted by epithelial cells ,

• collagen, laminin, proteoglycans, glycoproteins

• connects epithelium to reticular lamina

basal lamina

extracellular matrix (ecm) + cells

what is connective tissue made up of?

ground substance + fibres

what is ecm made of?

• made of water, protein, polysaccharides / glycosaminoglycans (GAGS)

• GAGS are long, unbranched sugars

• GAGS + proteins = proteoglycans

ground substance components

• the negative charges in sulphate attract positive ions, therefore drawing in water through osmosis.
  

sulphated gags and binding water

protein core, sulphated GAGS join to it, forming ‘bristles’ like a brush. attached are glycoproteins, (links) to join HA to protein cores. this ground substance structure is most common in cartilage connective tissue.

‘like a bottle brush that's been dipped in water’ BECAUSE it is still highly polar and attracts water to make ground substance more jelly-like.

tell me about the structure of an aggrecan aggregate

• it lacks the special linker region (a special sugar sequence) that sulphated gags use to covalently bind to protein core

• joined to various proteoglycans through linker protein, GLYCOPROTEIN.

non-sulphated gags and binding water

• connects basal lamina to connective tissue

• produced by underlying fibroblasts

• fibrous proteins, fibronectin, collagen

reticular lamina

a non-sulphated GAG that is viscous and slippery; binds cells together, lubricates joints, and helps maintain the shape of the eyeball.

what is the function of hyaluronic acid?

an enzyme that breaks down hyaluronic acid, increasing permeability of ground substance to allow movement of cells and substances.

what is hyaluronidase and its function?

widely distributed, migratory cells that secrete protein fibres and components of the extracellular matrix. major in connective tissue.

what are fibroblasts and their function?

fat-storing cells located under the skin and around organs; store triglycerides.

what are adipocytes and their function?

fixed or wandering cells that engulf pathogens and debris at infection or injury sites.

what are macrophages?

found in gut, lungs, salivary glands, lymph nodes, spleen, and bone marrow.

where are plasma cells found?

cells near blood vessels that release histamine to dilate vessels and promote inflammation.

what are mast cells and their function?

white blood cells that migrate from blood into tissues to respond to infection.

what are leukocytes in connective tissue?

embryonic connective tissue that gives rise to all other connective tissues; contains cells in semi-fluid ground substance with reticular fibres.

what is mesenchyme?

the most common connective tissue; contains collagen, reticular, and elastic fibres; functions in support, elasticity, and packing under epithelium.

what is areolar connective tissue?

tissue dominated by adipocytes for energy storage and insulation. stores energy as triglycerides.

what is adipose connective tissue?

buttocks, flanks, abdomen, orbit of the eye.

where is adipose tissue found?

reticular cells forming a framework (stroma) in organs, a filter for microbes lymph nodes and spleen.

what is reticular connective tissue?

more fibres and fewer cells, mainly collagen

what characterises dense connective tissue?

parallel collagen fibres found in tendons, ligaments, aponeuroses. provides strength along one axis.

what is dense regular connective tissue?

contains elastic fibres, allows stretch and recoil. found in lungs, arteries and vocal chords.

what is elastic connective tissue?

cells (chondrocytes) and extracellular matrix.

cartilage components

smooth, resilient cartilage with fires not obvious. found in nose, trachea, bronchi, ends of long bones.

hyaline cartilage

strongest cartilage with dense collagen, found in intervertebral discs, pubic symphysis and menisci.

what is fibrocartilage?

mesenchyme stem cells that differentiate into ostebolasts and begin collagen production

what are osteogenic cells

bone-forming cells that secrete collagen and initiate mineralisation

what are osteoblasts

mature bone cells that maintain tissue and exchange nutrients via gap junctions

what are osteocytes

multinucleated cells that break down bone for remodelling and mineral release

what are osteoclasts

osteoclasts remove dead bone, chondroblasts form cartilage, osteoblasts form new bone, osteoclasts remodel.

what are the steps of bone repair?

red blood cells without a nucleus; transport oxygen and carbon dioxide.

what are erythrocytes?

the ability to engulf and digest pathogens or debris.

what does phagocytic mean?

phagocytose and destroy bacteria.

what do neutrophils and monocytes do?

release histamine to promote inflammation.

what do basophils and mast cells do?

fight parasites and participate in allergic responses.

what do eosinophils do?

mediate immune response and produce antibodies

what do lymphocytes do?

large bone marrow cells that produce platelets

what are megakaryocytes?