Building bodies 1: Cells to tissues

next: - complete the slides which i left incomplete - add on whats in the end of the pdf to this

What are cells arranged into?

tissues

What is a tissue

a collection of similar cells ± support cells

Where do tissues come from

the 3 embryonic primary germ layers

What are the 3 primary germ layers

• Ectoderm

• Mesoderm

• Endoderm

What are the 4 basic tissue types?

• epithelium

• connective tissue

• muscle

• nerve

What is epithelia?

• covering and lining of membranes of the body, so have a free surface

• many types of epithelium, e.g., in lungs, tongue

• separated from the surrounding tissue by the basement membrane

• are specialised according to function (e.g., surface specialisations/cell junctions)

  • protect underlying tissue from outside world

  • protects/separates areas within the body

  • helps hold tissues together

  • thermoregulation

  • hormone release

  • absorption

Where do we find epithelia?

• epithelia on surface

• endothelium (sub) - lining blood vessels

• mesothelium (sub) - lining body cavities

Only bottom layer of epithelia attached to the basement membrane

.

Classification of epithelial cell layers

Simple squamous

Simple cuboidal

Simple columnar

Pseudo-stratified

Stratified squamous

Transitional

simple

1 layer

(in gut and gall bladder)

stratified

many layers

squamous

flat

columnar

taller than wide

in 3 dimension

cuboidal

square shaped

good for blood flow

in 3 dimension

low

What does simple squamous epithelium look like?

Where is simple squamous epithelium located?

• Airsacs of lungs

• lining of the heart

• blood vessels

• lymphatic vessels

What is the function of the simple squamous epithelium?

• Allows materials to pass through by diffusion and filtration

• Secretes lubricating substances

What does the structure of simple cuboidal epithelium look like?

Where is simple cuboidal epithelium located?

• In ducts and secretory portions of small glands and in kidney tubules

What is the function of simple cuboidal epithelium?

Secretes and absorbs

What does simple columnar epithelium look like?

Where is the simple columnar epithelium located?

• Ciliated tissues in:

  • larger bronchioles

  • uterine tubes

  • uterus

• Smooth (non-ciliated tissues) in:

  • digestive tract

  • bladder

What is the function of simple columnar epithelium?

• Absorbs

• secretes mucus and enzymes

What does pseudostratified columnar epithelium look like?

Where is pseudostratified epithelium located?

Ciliated tissue lines the bronchi, trachea, and much of the upper respiratory tract

What is the function of pseudostratified epithelium?

Secretes mucus; ciliated tissue moves mucus

What does the stratified squamous epithelium look like?

What is the location of stratified squamous epithelium?

Lining of:

• esophagus

• mouth

• vagina

What is the function of stratified squamous epithelium?

Protects against abrasion

What does stratified cuboidal epithelium look like?

What is the location of stratified cuboidal epithelium?

• sweat glands

• salivary glands

• mammary glands

What is the function of stratified cuboidal epithelium?

Protective tissue

What does the stratified columnar epithelium look like?

Where is the stratified columnar epithelium located?

• male and female urethrae

• ducts of some glands

What is the function of stratified column epithelium?

• secretes

• protects

What does transitional epithelium look like?

Where is transitional epithelium located?

Lining of:

• bladder

• urethra

• ureters

What is the function of transitional epithelium?

Allows the urinary organs to expand and stretch

Cilia that waft mucus, have gaps with goblets tails at the bottom, linked to gas exchange

.

e.g., urothelium/transitional epithelium characteristics

• protective

• stretches a lot

• secretory/absorptive

• facilitate diffusion

stratified squamous

mouth

simple squamous

alveolar

simple squamous

endothelium layers

What is a basement membrane

sheets of matric at the interface of function tissue (epithelium) and support tissue (connective tissue)

composed mainly of:

• type IV collagen

• glycoproteins (laminin secreted by epithelial cells)

• Fibronectin from fibroblasts and glycosaminoglycans

What is basement membrane mainly composed of?

• type IV collagen

• glycoproteins (laminin secreted by epithelial cells)

• Fibronectin from fibroblasts and glycosaminoglycans

Functions of basement membrane

• adhesion

• barrier (permeability)

• organisation of cells (controlling growth and differentiation)

Pathology of the basement membrane (BM)

• Disorders:

  • renal disease

  • cancer

  • genetic disease

• Skin pathology:

  • epidermolysis bullosa - separation of epidermis and dermis

  • blistering

If you want more secretion then? Or when you need to protect it?

Fold the epithelium

Make glands

(sweat glands have ducts)

Generally, secretory portion are

columnar

Generally ducts are

cuboidal epithelium

Shapes of gland

• tubular, acinar or mixed

• in its simplest form it is a single cell e.g., Goblet cell in the GI tract

• simple or compound (branched)

A great majority of cancers are derived from epithelial cells. What are these called?

Carcinomas

Cancer in glands is called adenocarcinoma

what can glands produce

• hormones

• sweat

• saliva

• mucus

• acids

What are the 2 types of glands?

Exocrine and endocrine

What do exocrine glands do?

secrete their products onto the epithelial surface directly or via a duct for local action e.g., sweat glands, liver

What do endocrine glands do?

release their secretions directly into the blood to act on different tissues e.g., pituitary and thyroid glands

Collagen is a connective tissue

made of 3 separate collagen molecules wrapped together in an alpha helix

support tissue of body

Where does (collagen) originate from

embryonic mesoderm

What are connective tissues made of?

cells, fibres and matrix

What are connective tissues characterised by

by the abundance of the matrix with few cells

What is connective tissue made up of?

cells (5%)

extracellular matrix (ECM) (95%)

What is ECM composed of?

• fibres (collagen and elastin)

• ground substance (glycoproteins and glycosaminoglycans)

What secretes ECM for most tissues?

the fibroblast

What is collagen

• a structural protein

• provides tensile strength and structural strength and structural support

• there are at least 16 different types but mainly types I,II, III (reticulin) and IV

What does elastin provide

Elasticity

Collagen synthesis, how many steps would i like to memorise this in haha

4

Step 1 of collagen synthesis

Procollagen polypeptide chains are synthesized on the ribosomes of the rough endoplasmic reticulum and secreted into the lumen,

Step 2 of collagen synthesis

where they are modified by hydroxylation of certain proline and lysine residues and glycosylation before chain association and triple helix formation

Step 3 of collagen synthesis

The procollagen molecules are secreted into the extracellular space where the N and C propeptides are cleaved by specific proteases.

Step 4 of collagen synthesis

The collagen molecules then assemble into fibrils, which are stabilized by the formation of covalent crosslinks

Collagen structure in detail

• provide tensile strength

• reduced tensile strength from collagen disorders causes tissue laxity, joint hypermobility and susceptibility to injury e.g., Ehlers-Danlos syndrome (type 1 collagen disorder)

pic of collagen fibres

fibroblasts with fibrocytes

Reticulum

Type III collagen - branched

Elastin fibres do what

stretching and elastic recoil

What polymerises to elastin?

tropoelastin

What do elastin fibred require for assembly?

fibrillin

Marfans syndrome

genes coding for fibrillin defective - rupture of strucaorta

structural glycoprotein examples

• Fibrillin - microfibrils 8-12nm - links to elastin

• Fibronectin - deposition and orientation of collagen and its links to cells via integrin

• Laminin - major component of Basement Membrane

What is Glycosaminoglycan (GAG)

polysaccharide chains that attract water

What are the 4 groups of GAGs

• Chondroitin sulfate

• Heparan sulfate

• Hyaluronan

• Keratan sulfate

GAGs form the centre of the intervertebral disc, forming what?

a compression resistant core

What about this pic of GAG?

GAGs form the centre of the intervertebral disc forming a compression resistant core

Why is histology the connective tissue looks pale pink with few cells (because epithelium is purple)

The properties of connective tissue are varied and result from the characteristics of what?

the extracellular matrix

What provides multiple tissue types?

Variation in the type, composition and arrangement of the macromolecules

What does connective tissue form

the structural framework of many body tissues

What are the 4 structural frameworks of connective tissue and give examples of each

1. Loose: packing material

2. Dense: tough physical support - dermis, organ capsule, ligaments, tendons

3. Areolar: fatty

4. Specialised support: cartilage and bone

Organisation and function of connective tissue: metabolic?

adipose tissue

Organisation and function of connective tissue: immune?

contains immune cells

(mast cells, tissue macrophages, WBCs, plasma cells) and effect repair

Organisation and function of connective tissue: mechanical and structural role?

carry blood and lymph vessels

Organisation and function of connective tissue: exchanges?

Mediate exchanges of nutrients, metabolites, and waste products from blood and tissues

Give examples of the range of connective tissue types

• fibrous connective tissue (forming a tendon)

• cartilage (at the end of a bone)

• adipose tissue

• bone

• blood (because it has a matrix - plasma)

• loose connective tissue (under the skin)