Integrating Cells Into Tissues, Organs And Systems

Question 1

Define tissue

Answer 1

A group of similar cells that work together to form a specific function or a specific set of functions within an organism.

Question 2

Define organ

Answer 2

The organisation of two or more tissues that have specific functions within an organism.

Question 3

In what order are epithelial cell adherence systems to the lateral surface from top to bottom and what do they do?

Answer 3

Tight junction
Adhesion junction
Dermosome
Gap junction

(TADG)

Question 4

How are cells held together at the molecular level?

Answer 4

• Cell-cell adhesion molecules
• Extra cellular matrix proteins
• Internal-external scaffolding that links the matrix proteins to inside the cell
• Close proximity (pressure effects)

Question 5

What is the role of connective tissue?

Answer 5

To attach epithelial tissue to smooth muscle.

Question 6

Where do epithelial cells line?

Answer 6

All cavities and free surfaces of the body.

Question 7

What are tight junctions and where are they located?

Answer 7

On the lateral surface, nearest to the lumen/apical surface.

They prevent large molecules moving through the apical surface into the deeper tissue layers.

Check notability for image.

Question 8

What is paracellular transport?

Answer 8

When tight junctions in the gut opens to allow small molecules to cross to the underlying tissues.

Question 9

What are adhesion junctions and where are they found?

Answer 9

In pairs on the lateral surface 1/3 distance from luminal surface.
Linked to E-Cadherin proteins, calcium ions are used to make these junctions.
Stabilising factor and additional transport barrier.

Photo on notability.

Question 10

What gives rise to the different epithelia?

Answer 10

All 3 germ layers.
Ectoderm: oral and nasal mucosae, cornea, epidermis of skin, mammary glands.
Endoderm: liver, pancreas, lining of respiratory and GI tract.
Mesoderm: urinferous tubules of kidney, lining of male and female reproductive systems, endothelial lining of circulatory system, mesothelium of body cavities.

Question 11

What are the functions of epithelial tissues?

Answer 11

• Protection from abrasion (oesophagus).
• Transcellular transport across epithelial sheets.
• Secretion of mucinogen.
• Absorption of material from lumen (intestinal tract, kidney tubules).
• Selective permeability.
• Detection of sensations (taste buds, retina of eye, specialised hair cells in ear).

Question 12

What is all epithelium connected to?

Answer 12

A basement membrane.

Question 13

What is dermosome and where are they found?

Answer 13

The strongest cell-to-cell adhesions. Found 1/2 way between the top and bottom of the cells on the lateral surface.
Found I tissues that experience stress - anything that expands e.g. cardiac muscle, bladder tissue, pregnant uterus.
The only cell-to-cell adhesion found in the upper epidermal (skin) cells.

Provide mechanical strength and prevent tissue destruction.

Question 14

What are gap junctions and where are they found?

Answer 14

Close to the base of epithelial cells on the lateral surface.
They allow free movement of small molecules from one cell to another - ions, sugars, amino acids.
Important in smooth muscle contractions. They open and close.

In all cells except spermatozoa, erythrocytes and nerves.

Question 15

What are the cell adherence systems on the lateral surface in order from apical to basal surface?

Answer 15

Tight junctions
Adhesion junctions
Dermosome
Gap junctions
Cell adhesion molecules

Question 16

What are the cell adherence systems on the basal surface?

Answer 16

Hemi-dermosome
Focal adhesions
Integrons
Proteoglycans
Cell adhesion molecules

Question 17

What are Hemi-dermosomes and where are they found?

Answer 17

Found on basal surface of epithelial cells.

Attaches to a layer of extra cellular matrix.
Anchors epithelial cells to basal lamina and prevents loss to external surface. Intracellular intermediate filaments of cytokeratin attached to lamina through integrons.

Question 18

What are focal adhesions and where are they found?

Answer 18

Attachment of cell to basal lamina like Hemi-dermosomes, but use intracellular actin filaments instead of cytokeratin.
Binds to firbonectin instead of laminin.

Question 19

What are integrins and where are they found?

Answer 19

They bind weakly.
Central to cohesive forces holding tissues together.
Phosphorylation by FOCAL ADHESION KINASE produces heterotetramer which binds strongly for example, in skin and blastocyst attachment to endometrium.

Question 20

What leads to organ formation?

Answer 20

Tissues adhere to other types of tissue (e.g. nerves to blood vessels) through connective tissue fibres.

Question 21

How do cells that touch each other communicate?

Answer 21

Through gap junctions.

Question 22

What is the mucosal membrane and what are its functions?

Answer 22

The moist, inner lining of some organs and body cavities.

Functions:
- To stop pathogens and dirt from entering the body.
- Prevent body tissues from becoming dehydrated.
- To lubricate the surface.

Question 23

Describe the structural relationships between the epithelia and the oesophagus.

Answer 23

The epithelium is stratified squamous and non-keratinised so it can withstand abrasion.
The submucosa contains mucus secreting glands.
Muscularis externa has smooth muscle layers that move a bolus of food by peristalsis.

Question 24

Describe the structural relationships between the epithelia and the stomach.

Answer 24

Gastric mucosa secretes acid, digetstive enzymes a the hormone gastrin.
Muscularis externa - 3 layers of smooth muscle.
Rugae folds of gastric mucosa forming longitudinal ridges in empty stomach.

Question 25

Describe the structural relationships between the epithelia and the jejunum (part of small intestine).

Answer 25

Jejunal mucosa - simple columnar epithelium. Contain villi which increase SA and globule cells which make mucus.

Question 26

Describe the structural relationships between the epithelia and the large intestine (colon).

Answer 26

Simple columnar epithelium of the crypts produces mucus and supplies cells to the surface.
Surface epithelial cells absorb water and electrolytes.

Question 27

Explain the function of mucosa in the GI tract.

Answer 27

1. To ABSORB substances from the lumen.
2. To PREVENT ingress of PATHOGENS.
3. MOVE contents and EXPEL WASTE.

Epithelial cell specialisations help 1 and 2. - folding of mucosa. microvilli, peristaltic actions.
Muscularis externa performs peristalsis to help 3.

Question 28

Describe the structural relationships between the epithelia and the kidney.

Answer 28

Bowman’s capsule is lined with squamous epithelial cells. The inner ones are called visceral epithelial cells and the outside ones are called parietal (warm) epithelial cells.

Question 29

What is Alport’s syndrome or basement membrane disease?

Answer 29

When the basement membrane of the urinary tract breaks down, causing fluid to break the tube apart. This leads to kidney failure.

Question 30

Describe the structural relationships between the epithelia and the urinary tract.

Answer 30

The corpuscle lining is squamous epithelium and the lining of collecting ducts is cuboidal epithelium.
The muscle layer appears in the ureter and bladder.
The epithelium is known as the urothelium and is transitional. This means it can expand when there is urine in it.

Question 31

Describe the structural relationships between the epithelia and the bladder.

Answer 31

• Epithelial cells produce mucus. This protects the bladder from damage by acidic urine.
• Tight junctions are very well protect which protects leakage to inner cell layers.

Question 32

Describe the structural relationships between the epithelia and the urethra.

Answer 32

This is the same as the bladder plus:
Epithelial cells change from transitional to squamous and then to keratinised squamous at the outlet.

Mucus glands produce a lot of sticky mucus to prevent ingress of pathogens.

Question 33

Describe the structure of the trachea and primary bronchi.

Answer 33

MUCOSA - epithelial layer is several cells deep and surface is covered with cilia. Lamina propria is very thin.
SUBMUCOSA - Connective tissue layer contains mainly collagen and elastin fibres and many fibroblasts. Also contain seromucis glands that produce watery mucus that thickens during infection.
C-SHAPED HYALINE CARTILAGE - to keep trachea open.

Question 34

What do secretions from the epithelium and submucosal glands of the trachea and bronchi contain?

Answer 34

Mucins and water (sticky mucus)
Serum proteins (for lubrication)
Lysozyme (destroys bacteria)
Anti-proteases (inactivates bacterial enzymes)

Question 35

Describe the mucocilary escalator.

Answer 35

Mucus moves materol to oral cavity quickly where it can be swallowed.

Thick basement membrane.
Lamina propria rich in immune cells with a layer of elastic fibres.

Question 36

How is secondary and tertiary bronchi different to primary.

Answer 36

Cartilage is not present as full circle of rings. Airway kept open with crescent shaped cartilage.

Question 37

What is the structure of the alveolus?

Answer 37

Capillaries lined with endothelium (flattened specialised epithelial cells) attached to fused basal lamina with even thinner epithelial cells.

At the junction, small amounts of collaged provide to the mucosa surrounded by elastin and fibrillin make elastic fibres to return the sac to the empty state on exhaling.

Question 38

What happens if the stereocilia become dysfunctional?

Answer 38

Difficulty sensing balance and tinitus.