Basic mammalian Tissue Structure

Question 1

Describe drug administration and absorption.

Answer 1

• Drugs must enter/leave bloodstream
• Drugs must penetrate tissues and distribute throughout

Question 2

State the two types of cell ‘barriers’.

Answer 2

Composed of epithelium or endothelium
- external absorption barriers e.g. modified epithelium
- internal barrier e.g. blood - tissue barriers

Question 3

State the 4 categories of tissue and the primitive layers (germ cell) they develop from.

Answer 3

• Connective tissue (from Mesoderm)
• Muscular tissue (from Mesoderm)
• Nervous tissue (from Ectoderm)
• Epithelium (mesoderm/ectoderm /endoderm)

Question 4

What is epithelia?

Answer 4

Tissues that act as protective layers and/or secretory components of body organs and systems

Question 5

State the common characteristics of epithelia that contribute to their functional capabilities.

Answer 5

• Formed into tightly cohesive cellular sheets
• Cover/line body surfaces e.g. alimentary canal and exocrine ducts
• Distinguishing tissue of most organs
• All the vital traffic of the body passes through the epithelial layer e.g. digested food, oxygen, secretions
  High capacity for regeneration e.g. wound healing, intestinal abrasion

Question 6

Describe the epithelia attribute limited intracellular space.

Answer 6

– Specialised intracellular junctions to hold cells close together.
– Effective barrier and blocks infiltration of fluids between cells

Question 7

Describe epithelia attribute single or multiple layers of cells.

Answer 7

– Where diffusion / filtration is important, epithelia is a single layer thick.
– Where protection from abrasion is required, epithelial is multicell thick

Question 8

Describe epithelia attribute free apical surfaces.

Answer 8

– During development or at maturity.
– Where cells of an epithelium face internal lumens.

Question 9

Describe epithelia attribute basement membrane.

Answer 9

– Attachment of epithelia to underlying connective tissue.

Question 10

Describe the epithelia attribute mitotic capability

Answer 10

• Enables repair and regeneration

Question 11

Describe the two structural characteristics epithelia are described as.

Answer 11

Arrangement of cells in layers
– Simple epithelium
– Pseudostratified epithelium
– Stratified epithelium

Cell shape
– Squamous cells
– Cuboidal cells
– Columnar cells
– Transitional cells

Question 12

Describe the different cell layers.

Answer 12

• Simple epithelia – one cell thick
• Stratified epithelia – many cells thick but only bottom layer in contact with basement membrane
• Pseudostratified epithelia – appear more than one cell thick but all cells
  rest on basement membrane

Question 13

Describe the different cell shape.

Answer 13

• Squamous – flattened like paving stones
• Columnar – taller than they are wide
• Cuboidal – similar height depth and width
• Transitional – layers which change their shape when they are stretched

Question 14

Where are simple squamous cells found.

Answer 14

alveoli and capillaries of lungs

Question 15

Where are simple cuboidal cells found.

Answer 15

Kidney tubule

Question 16

Where are simple columnar cells found.

Answer 16

Small intestine

Question 17

Where are transitional cells found.

Answer 17

• Only in urinary tract
• Stretches to accommodate fluid changes

Question 18

Where is stratified squamous found?

Answer 18

Oesophagus

Question 19

Where are keratinised stratified squamous?

Answer 19

• Only found in skin

Question 20

Where are pseudo stratified layers found?

Answer 20

Trachea, nasal mucosa

Question 21

Where are stratified cuboidal cell layers found?

Answer 21

Sweat gland duct

Question 22

Describe simple squamous cells.

Answer 22

• lines blood vessels and air sacs of lungs
• permits exchange of nutrients, wastes and gases

Question 23

Describe stratified squamous.

Answer 23

• Outer layer of skin, mouth, vagina
• Protects against abrasion, drying out, infection

Question 24

Describe simple cuboidal cells.

Answer 24

• Lines kidney tubules and glands
• Secretes and reabsorbs water and small molecules

Question 25

Describe stratified cuboidal cells.

Answer 25

• Lines ducts of sweat glands
• Secretes water and ions

Question 26

Describe the simple columnar cells.

Answer 26

• Lines most digestive organs
• Absorbs nutrients, produces mucus

Question 27

Describe stratified columnar.

Answer 27

• Lines epididymus mammary glands, larynx
• Secretes mucus

Question 28

Describe modifications of the basal surface.

Answer 28

• Basement membrane = basal lamina (selectively permeable filter)

Question 29

Describe modifications of the apical surface.

Answer 29

• Microvilli - finger-like extensions of the plasma membrane and increase surface area for absorption’s e.g. small intestine
• Cilia - whip-like, motile extensions, moves mucus etc over epithelial surface in one direction e.g. trachea and respiratory bronchus

Question 30

Describe modifications of the lateral surface.

Answer 30

• Adhesion Junctions - adhesive spots (Desmosomes) on lateral sides, involves cadherin proteins
• Tight Junctions – apical plasma membrane of adjacent cells fuse - Nothing passes. e.g. GI tract (prevents enzymes entering bloodstream)
• Gap Junctions - Spot-like junctions allowing small molecule passage

Question 31

Describe the glandular epithelium.

Answer 31

Aggregates of epithelial cells clustered together to perform specific secretory or excretory function

Question 32

What products do glandular epithelium secrete?

Answer 32

– Hormones
– Enzymes
– Milk
– Sweat
– Mucous
– Oil

Question 33

State the glandular classifications.

Answer 33

• EXOCRINE
  – Pour products into ducts that open into lumen of organ or
  onto the skin
• ENDOCRINE
  – Have no duct system – ductless glands – secrete into empty
  tissues spaces – eventually enter blood stream

Question 34

Describe the morphological classifications of exocrine glands.

Answer 34

Simple – single tube
Compound – branched duct system

Secretory
- Tubular
- Acinar/Alveolar (grape like)
- Saccular (pouch like)

Question 35

Describe the secretory mechanism merocrine

Answer 35

– e.g. salivary gland - secretion passes from cells without
damage to plasma membrane – exocytosis
– Most glands secrete in this way

Question 36

Describe the secretory mechanism holocrine.

Answer 36

– e.g. sebaceous gland –cellular debris part of secretion (sebum)
– involves death of the cell

Question 37

Describe the secretory mechanism apocrine

Answer 37

– e.g. mammary gland –
– apical end pinched off

Question 38

Define membranes.

Answer 38

Thin sheets of flexible tissue that line or cover parts of the body

Question 39

Describe serous membranes.

Answer 39

• Line closed body cavities, secrete a watery serous fluid
• Simple squamous (generally),resting on thin layer connective tissue
• Parietal layer attaches to the body wall around the organ
• Visceral layer attaches to the organs themselves

Question 40

Describe mucous membranes.

Answer 40

• Line cavities open to outside
• Mucous cells / glands lumen of digestive(microvilli), reproductive,
  respiratory tracts (ciliated)
• Epithelial cells vary in morphology & function

Question 41

Describe cutaneous membranes.

Answer 41

Cutaneous membrane is the skin, covering the outer surface of the body
– Keratinised squamous epithelium

Question 42

Describe synovial membranes.

Answer 42

Synovial membranes line cavities of freely movable joints,
– Incomplete epithelium
– Contain connective tissues

Question 43

Describe epithelial absorptions barriers.

Answer 43

– Cells connected via tight junctions to create an unbroken epithelium
– Drugs MUST cross the liphophilic epithelial plasma membrane to
enter the body (except parenteral)

Question 44

Describe blood-tissue barriers.

Answer 44

– Endothelial cells connected into continuous barrier via tight junctions
– Differences in capillary beds between tissues

Question 45

Describe membrane permeation.

Answer 45

– Passive diffusion – compounds high lipid solubility, dependency on
drug charge and pH
– Active Transport – Drugs ‘hijack’ cellular transporters
– Receptor Mediated Endocytosis – Endosomal vesicles, then recycled
to cell surface