Lecture 6

Question 1

Types of epithelial tissue.

Answer 1

Exchange epithelium, transport epithelium, protected epithelium (mouth and genitals), and secretory epithelium.

Question 2

Transcytosis.

Answer 2

Occurs across the capillary endothelium through red blood cells calveolae.

Question 3

Cystic fibrosis case study.

Answer 3

Causes: mutation-function at the cell level. Salty skin: a normal gland secretes chloride and sodium ions, but a faulty chloride channel (CFTR gene) will lead to an inability to release chlorine and sodium ions properly (these ions stick together). Water follows sodium, which causes very thick secretions. Thick mucus stays trapped in the lungs; cilia cannot work because the mucus is too thick due to lack of water in it. Coughing is a symptom of blocked airways, damage to airways, runny nose, salty skin. There are also digestive issues: pancreatic duct is clogged due to thick mucus, so digestive enzymes cannot reach the duodenum; he has diarrhea because he cannot break down or absorb anything.

Question 4

Characteristics of cystic fibrosis.

Answer 4

Faulty gene is located on the long arm of chromosome 7 (CFTR). Malfunction leads to defective cAMP-activated chloride and sodium channels found on many epithelial cells. NaCl becomes trapped in the cell and pulls water in, leading to dehydrated mucus. Lungs are the most affected organs, but other secretory organs are also affected.

Question 5

Genetic component of cystic fibrosis.

Answer 5

Both of the patient’s parents are carriers; the patient is homozygous recessive. More than 1 100 gene mutations are associated with CF. Example: missing TTT (508), which is phenylalanine.

Question 6

Molecular mechanism of cystic fibrosis.

Answer 6

Missing amino acid as a consequence of genetic mutation, the wrong mRNA is made, which produces a faulty chloride channel (or no chloride channel); water remains in the cell due to hypertonicity, blocking passageways and ducts.

Question 7

Which cells secrete mucus?

Answer 7

Goblet cells.

Question 8

Treatments for cystic fibrosis.

Answer 8

Airway clearance therapy, antibiotics, bronchial dilators, vitamin supplements (as the patient is not absorbing many nutrients due to lack of digestive enzymes), and enzymes to aid digestion.

Question 9

Cell potency classification.

Answer 9

Totipotent (can form anything), pluripotent (-blasts are present), and multipoint.

Question 10

How can pluripotency of a cell be induced?

Answer 10

Force a fully mature cell into expressing 4 specific genes.

Question 11

Transporting epithelium: tubules in the nephron of the kidney.

Answer 11

Tubules are responsible for absorption and secretion.

Question 12

Key to homeostasis.

Answer 12

Cell-to-cell communication.

Question 13

2 types of physiological signals for communication in the body.

Answer 13

Electrical signals and chemical signals.

Question 14

Electrical signals.

Answer 14

Involve changes in membrane potentials, can be seen in the nervous system.

Question 15

Chemical signals.

Answer 15

Molecules secreted by cells into extracellular fluid, responsible for most of the communication within the body. Endocrine system: hormones are chemical signals.

Question 16

4 basic method of cell-to-cell communication.

Answer 16

Gap junctions, contact-dependent signals, chemicals that diffuse through ECF to act on cells nearby, and long-distance communication.

Question 17

Gap junctions.

Answer 17

Allow direct cytoplasmic transfer of electrical and chemical signals between adjacent cells.

Question 18

Contact-dependent signals.

Answer 18

Occurs when surface molecules on one cell membrane bind to surface molecules on another.

Question 19

Chemicals the diffuse for signalling.

Answer 19

Paracrine or close-acting signals.

Question 20

Long-distance communication.

Answer 20

Combination of chemical signals transported by the blood. Seen in the endocrine system.

Question 21

Characteristics of gap junctions.

Answer 21

Simplest form of cell-to-cell communication, involves direct transfer of electrical and chemical signals, creates cytoplasmic bridges between adjacent cells, forms membrane-spanning proteins called connexins, allows ATP, cAMP, and amino acids to diffuse directly across cells when open. Larger molecules cannot pass through. This is the only way electrical signals can pass from cell to cell.

Question 22

Contact-dependent signalling.

Answer 22

Surface molecules on one membrane bind to those on another membrane, occurs in the immune system and during growth, includes CAMs (cell-adhesion molecules). Seen on immune cells: they display an antigen on the surface to neighbouring cells.

Question 23

Direct contact and local cell-to-cell communication.

Answer 23

Paracrine signals (close proximity) and autocrine signals (act on the same cells that secreted them; secretes a ligand that binds to its own receptor).

Question 24

Paracrine.

Answer 24

Acts on cells at close proximity.

Question 25

Autocrine.

Answer 25

Acts on itself; ligand secreted by the cell binds to a receptor in the cell.

Question 26

Long distance communication.

Answer 26

Chemical messengers enter the bloodstream (like when hormones are secreted into the blood through endocrine glands). It only targets cells with the specific receptor.

Question 27

Endocrine system covers…

Answer 27

Long-term effects.

Question 28

Nervous system covers…

Answer 28

Fast-acting, short-term effects.

Question 29

Neurons use which type of signalling?

Answer 29

Both electrical and chemical signalling.

Question 30

Neurohormones.

Answer 30

Chemicals released by neurons into the blood for action at distant targets.

Question 31

Cytokines.

Answer 31

Synthesized and secreted by all nucleated cells. Control cell development, differentiation, and immune response. They act on a broader spectrum of target cells than hormones, and they are made on demand.

Question 32

Function of cytokines.

Answer 32

Control cell development, differentiation, and immune response.

Question 33

Signal pathway of paracrine and autocrine molecules.

Answer 33

All signal pathways share the following features: signal molecule (ligand or first messenger) brings information to the target cell, ligand-receptor binding causes a conformational change which activates the receptor, the receptor then activates one or more intracellular signal molecules, and the last signal ,molecule initiates the synthesis of target proteins or modifies the existing target protein to generate a response.