Platelet Ultrastructure (P)

Question 1

What are the different zones of platelet ultrastructure?

Answer 1

1) Peripheral zone
2) Sol-gel zone
3) Organelle zone
4) Membranous zone

Question 2

What are the components of peripheral zone?

Answer 2

It contains glycoproteins

Question 3

What are the components of sol-gel zone?

Answer 3

It contains microtubules and microfilaments

Question 4

What are the components of organelle zone?

Answer 4

It contains platelet granules

Question 5

What are the components of membranous zone?

Answer 5

It contains membrane systems

Question 6

What are the components of resting plasma membrane?

Answer 6

1) Predominant lipids
2) Outer, blood plasma layer
3) Inner, cytoplasmic layer
4) Glycoproteins and proteoglycans
5) Glycocalyx

Question 7

What are the component of predominant lipids?

Answer 7

1) Phospholipids

2) Cholesterol

Question 8

What is the function of cholesterol?

Answer 8

It stabilizes the membrane and maintains fluidity

Question 9

What are the components of outer, blood plasma layer?

Answer 9

1) Phosphatidylcholine

2) Sphingomyelin

Question 10

What are the components of inner, cytoplasmic layer?

Answer 10

1) Phosphatidylinositol
2) Phosphatidylethanolamine
3) Phosphatidylserine

Question 11

What is the purpose of phosphatidylinositol?

Answer 11

It supplies arachidonic acid

Question 12

What is the purpose of glycoproteins and proteoglycans?

Answer 12

These responds to ligands or agonists

Question 13

What is glycocalyx?

Answer 13

1) It is the surface of PLT membrane

2) Adhesive and absorbs albumin, fibrinogen, and other plasma proteins

Question 14

What is the purpose of cytoskeleton?

Answer 14

1) Control PLT shape change
2) Extends pseudopods
3) Secretes granule contents

Question 15

What are the components of cytoskeleton?

Answer 15

1) Circumferential microtubules
2) Meshwork of filaments
3) Intermediate microfilaments

Question 16

What are the characteristics of circumferential microtubules?

Answer 16

Resides beneath the plasma membrane

Question 17

What are the functions of circumferential microtubules?

Answer 17

1) Maintains the discoid shape of PLT
2) Provide rigidity to pseudopods
3) Express alpha (insert sign)-granule contents during PLT activation

Question 18

What are the characteristics of meshwork of microfilaments?

Answer 18

1) Resides between plasma membrane and microtubules

2) Composed of actin which allows the PLT to contract

Question 19

What is the purpose of intermediate microfilaments?

Answer 19

Maintains PLT shape

Question 20

What are the 2 components of intermediate microfilaments?

Answer 20

1) Desmin

2) Vimentin

Question 21

What is the function of desmin and vimentin?

Answer 21

To connect tubules to membrane

Question 22

What are alpha (insert sign)-granules?

Answer 22

1) 50-80 granules per PLT
2) Fuse with SCCS to release their contents
3) Stain medium gray in osmium dye-TEM

Question 23

What are dense granules?

Answer 23

1) 2-7 per PLT
2) No membrane system used; release contents directly to plasma
3) Stain black opaque in osmium dye-TEM

Question 24

What is the function of lysosomes?

Answer 24

To digest autophagic debris

Question 25

Lysosomes stain positive for what?

Answer 25

Lysosomes stain (+) for arylsulfatase, beta (insert sign)- glucoronidase, acid phosphatase, and catalase

Question 26

What are the 2 types of system under membrane system?

Answer 26

1) Surface-Connected Canalicular System

2) Dense Tubular System

Question 27

What is the meaning of SCCS?

Answer 27

Surface-Connected Canalicular System

Question 28

What is SCCS?

Answer 28

1) Sponge-like
2) Enables PLT to store additional proteins
3) Route for endocytosis
4) Secretion of alpha-granule contents

Question 29

What is the meaning of DTS?

Answer 29

Dense Tubular system

Question 30

What is DTS?

Answer 30

1) A condensed RER remnant
2) Sequesters ^Ca2+
3) Holds a number of PLT activation enzymes