Epithelium and Connective Tissue

Question 1

Tight Junctions

Answer 1

Separates lumen from basal/lateral layers. Cells that make up this connection are proteins including occludin, claudin, zonulin, and catenin.

Question 2

Spot desmosomes are held together

Answer 2

Desmogleins and desmocollins (b/t cell) and intermediate filaments (inside each cell)

Question 3

Belt desmosomes are held together by

Answer 3

E-cadherins (b/t cells) and actin microfilaibrinments (inside each cell)

Question 4

Hemidesmosomes are held together by

Answer 4

Integrin (b/t cell and basement membrane) and intermediate filaments (inside cell) and laminin (in basement membrane)

Question 5

Gap Junctions

Answer 5

Holes between cells made by hexamer of transmembrane proteins called connexins.

Question 6

Type I collagen formation, function, and location

Answer 6

RER of fibroblasts make procollagen (triple helix). Processed in RER and Golgi then secreted out of cell. Propeptides on procollagen are cleaved to make tropocollagen. Then it self assembles into collagen fibrils which form fibers.

Located in reticular dermis.

Vitamin C is required for this synthesis.

-Mechanical Reinforcement.

Question 7

Defects in Type 1 collagen result in…

Answer 7

Ehlers Danlos Syndrome. Hyper-elasticity of skin and hyper-flexibility of joints

Question 8

Type III collagen function and location

Answer 8

Main support of loose connective tissue. Forms 3D network/scaffolding.

• AKA reticular fibers
• secreted by fibroblasts called fibroblastic reticular cells aka mesenchymal reticular cells.
• Supports organs such as lymph nodes, spleen, and liver.
• main type of collagen in liver and lamina propia of gut

Question 9

Type III collagen defect results in

Answer 9

Ehlers Danlos Syndrome (Type IV). Defects in structural stability of organs especially blood vessels and intestines. (vascular defects)

Question 10

Elastic fibers function and structure

Answer 10

Confer elasticity on connective tissue. Synthesized by smooth muscle and fibroblasts as tropoelastin. Once secreted it is made into fibers via fibrillin (for skin). Also can be made into sheets for blood vessel (elastic lamella).

• contains hydrophobic regions giving it elasticity.

Question 11

Proteoglycans:

Answer 11

• Contain protein core with glycosaminoglycan side chains (GAGs).
• GAGs are negatively charged and attracts water which helps resist compression.

Question 12

Fibronectins:

Answer 12

Adhesive glycoproteins that bind cells to collagen I and III. They bind to integrins.

• Plays role in cell migration.
• V shaped
• important in white blood cell movement in CT

Question 13

Laminin:

Answer 13

• Adhesive glycoproteins which bind to integrins in basal membrane of epithelia cells to type 4 collagen. It is a component of the basement membrane (basal lamina).
• Different from fibronectin because it anchors rather than mediates movement.

Question 14

Type IV Collagen is found

Answer 14

-In basement membrane(aka basal lamina). Laminin bind integrin to Type IV Collagen.

Question 15

Type VII Collagen is found

Answer 15

-Found in dermis of skin. Laminin (most likey) binds integrin to collagen which is connected to dermis.

Question 16

Hyaluronan function

Answer 16

-Glycosaminoglycan (GAG) that isn’t attached to protein core. Found in cartilage. Binds aggrecan (a proteoglycan), provides strong resistance to compression.

Question 17

Fibrin, Fibrillin, Fibronectin, Fibrils

Answer 17

Fibrin: plays role in clotting
Fibrillin: helps elastin form fibers
Fibronectin: binds to type 1 and 3 collagen
Fibrils: part of a fiber