BIOL 1410 Lecture Notes - Lecture 7: Epithelium, Free Surface, Histology

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maroonduck204

1 May 2018

School

University of Manitoba

Department

Biological Sciences

Course

BIOL 1410

Professor

Paul G.Messing

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TOPIC 7: HISTOLOGY (TISSUES)

A) Histology?

 the study of tissues

 Tissue

o a group of cells with similar structure and function

o 4 major tissue types:

 Epithelial Tissue

 Connective Tissue

 Muscle Tissue

 Nervous Tissue

A) Cell Junctions (in some tissues) figure 4.3b

 points of contact between adjacent cells - seen in epithelial tissue, some

nervous and muscle cells

 formed by cell membrane proteins

 3 types of cell junctions: anytime you have a junction, you’re making them up

from proteins

1) Tight Junctions figure 3.5

 Holding the cells tightly together – prevents things from passing

through them

 are a partial fusion of specific proteins on the lateral surface of

the cell membrane

 form ring-like tight seal

 prevents material from passing between cells e.g. bacteria,

proteins, sometimes fluid or ions (depending on the tissue)

2) Anchoring Junctions (e.g. desmosomes)

 They are anchoring (holding) one cells to the next

 proteins that fasten cells to each other and/or extracellular

material (“rivets” cells together – anchoring cells to cells)

3) Gap Junctions figure 3.5

 open channels (formed by proteins) through the adjacent cell

membranes interconnecting the cytosols of the cells

 allows ions/small molecules to pass from one cell to another

 tissues can then work as a unit:

o important in cardiac and smooth muscle (allows

synchronization of contractions)

o also found in epithelial tissue

B) 4 Major Tissue Types (Overview)

1) Epithelial Tissue

 lining tissue

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2) Connective Tissue

 connecting tissue

3) Muscle Tissue

 contractile tissue

4) Nervous Tissue

 signaling tissue

➢ Epithelial Tissue

 covers body surface (skin)

 lines body/organ cavities (from the outside following in)

o organ cavity = lumen – is a space/cavity not a tissue

 Characteristics of Epithelia: “what are the overall characteristics of Epthelia?”

o has one free surface – does not have to be the ‘outside air’; it can be in

contact with the blood or surrounded by cell rings – its not = to air

o little extracellular space between cells

o avascular – no blood vessels

o Basement membrane – its bellow the epithelia tissue*

▪ extracellular layer

▪ attaches epithelium to underlying CT layer (formed by both

tissues – “velcro”)

 Classification of Epithelia:

o most subtypes are classified + named according to:

▪ # of cell layers sitting on the basement membrane

• one layer = simple

• more than one layer = stratified

▪ shape of the cells in the apical layer (= layer touching the free

surface “so like the first row of cells”)

• flattened = squamous

• round or cube shaped = cuboidal

• rectangular = columnar

1) Simple Epithelia = 1 layer

▪ allow exchange of molecules (gasses, nutrients, etc.) –

absorption/secretion (getting things in or out)

▪ subtypes:

a) simple squamous (flattened) = 1 layer of squished (flat) cells

 e.g. lungs

b) simple cuboidal (look like little cubes)= 1 layer of cube

shaped cells

 e.g. kidneys

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Document Summary

Tissue: a group of cells with similar structure and function, 4 major tissue types: Nervous tissue: cell junctions (in some tissues) figure 4. 3b. Points of contact between adjacent cells - seen in epithelial tissue, some nervous and muscle cells. 3 types of cell junctions: anytime you have a junction, you"re making them up from proteins: tight junctions figure 3. 5. Holding the cells tightly together prevents things from passing through them. Are a partial fusion of specific proteins on the lateral surface of the cell membrane. Prevents material from passing between cells e. g. bacteria, proteins, sometimes fluid or ions (depending on the tissue: anchoring junctions (e. g. desmosomes) They are anchoring (holding) one cells to the next. Proteins that fasten cells to each other and/or extracellular material ( rivets cells together anchoring cells to cells: gap junctions figure 3. 5. Open channels (formed by proteins) through the adjacent cell membranes interconnecting the cytosols of the cells.

Related Questions

1. How does the extracellular matrix affect a cell that it surrounds? (Select all that apply.)

		The cell's shape depends in part on the structure and composition of the extracellular matrix.
		The genes that the cell expresses depend in part on the types of proteins in the extracellular matrix.
		The size that the cell grows to depends in part on the polysaccharides in the extracellular matrix.
		The extracellular matrix has no effect on the cells that it surrounds.
		All of these choices are correct.

2. Dynamic instability is the rapid assembly and disassembly of:

		microfilaments.
		intermediate filaments.
		microtubules.

3. Which one of the following is a characteristic shared by integrins and cadherins?

		Both are peripheral membrane proteins.

		Both are present in adherens junctions, desmosomes, and hemidesmosomes.
		The cytoplasmic domains of both proteins are connected to the cytoskeleton.

4. Which of the following is a mesh-like attachment between cells formed by binding of transmembrane proteins of one cell to the same protein type on the adjacent cell, preventing substances from passing between cells?

		a.) adherens junction
		b.)desmosome

		c.) tight junction

viridianlion889

1. Kinesin-1 motors can move long distances on microtubule tracks without dissociating. By contrast, myosin II motors in skeletal muscle take only one or a few steps before letting go. What is most likely the difference between these two motors that allow two different types of movement?

A. Differences in length of the stalk of each respective motor allow for differences in step size

B. Differences in ATP versus GTP hydrolysis alter the motor head movement along filaments

C. Actin filaments are smaller in diameter and have less space for movement

D. Binding affinity of the Kinesin-1 motor head to microtubules is high, whereas binding affinity of the myosin II motor head to actin filaments is low

E. Microtubules are larger in diameter and have more space for movement

2. Dynamic instability causes microtubules either to grow or to shrink rapidly. What is the most likely reason for a microtubule to undergo rapid growth?

A. GTP hydrolysis exceeds the rate of heterodimer addition

B. GTP hydrolysis of alpha tubulin causes an outward bend in the heterodimer conformation

C. A low concentration of tubulin heterodimers are in solution

D. Heterodimer addition exceeds the rate of GTP hydrolysis

E. Increased trafficking of microtubule motor proteins favors stability

3. There are no known motor proteins that move on intermediate filaments (IFs). What property of intermediate filaments would most likely explain the lack of motor proteins?

A. Tissue specific expression of IFs prevent a single type of motor protein to evolve over time

B. Lateral bundling of IFs prevent motor movement

C. IFs are less dynamic than microtubules and actin filaments

D. IFs are unpolarized

E. IFs do not bind a nucleotide

4. You discover a mutation that results in less rapid hydrolysis of GTP by the beta-tubulin subunit. What would most likely occur?

A. There would be no change in filament assembly

B. There would be enhanced instability of the microtubule

C. There would be enhanced stability of the microtubule

D. Microtubules would not form

E. There would be enhanced treadmilling

5. Which of the following statements describes common features of cadherins and integrins?

A. They can link to microtubules using specific adapter proteins

B. They mediate heterophillic interactions

C. They achieve high binding affinity through clustering

D. They are responsible for interactions of a cell with the extracellular matrix

E. They are found in the apical plasma membrane of an epithelial cell

6. Intermediate filaments are uniquely non-polar and built by lateral bundling in five steps: 1) synthesis of an alpha-helical monomer, 2) formation of a coiled-coil dimer, 3) formation of a staggered tetramer of two coiled-coil dimers, 4) lateral association of 8 tetramers, and 5) addition of 8 tetramers to a growing filament. At what step is polarity lost?

A. Step 1

B. Step 2

C. Step 3

D. Step 4

E. Step 5

7. Collagenase is an enzyme that breaks peptide bonds in collagen to help destroy extracellular structures. What would be the most likely reason to use collagenase in a cell biology laboratory?

A. Disrupt cadherin interaction with the extracellular matrix

B. Disrupt cell-cell contacts to passage cells in cell culture

C. Dissociate epithelial cells from the underlying basement membrane to separate tissues

D. All of the answers are likely uses for collagenase

E. Lyse cells to expose intracellular proteins and organelles

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BIOL 1410 Lecture Notes - Lecture 7: Epithelium, Free Surface, Histology

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