16 - Sperm Structure and Function

Question 1

Three sections of a sperm

Answer 1

Head
Mid Piece
Main Piece

Question 2

Parts of the sperm head

Answer 2

• Nucleus: oval and flattened, DNA highly condensed
• Acrosome: membrane-bound lysosome containing hydrolytic enzymes required for penetration of the oocyte zona pellucida at fertilization
• Post-nuclear cap: lower portion of sperm head not covered by acrosome

Question 3

What are acrosomal enzymes? What is the acrosome reaction?

Answer 3

Enzymes = hyalutonidase, acrosin, zona lysin, esterases, acid hydrolases (break down glycoproteins on oocyte)

Reaction = release of enzymes at time of fertilization (triggered by the egg binding proteins in sperm membrane)

Question 4

Slides 7, 8, 9

Answer 4

Sperm head, mid piece and principal piece

Question 5

What is the role of the tail axoneme

Answer 5

Responsible for sperm motility

Question 6

Describe the tail axoneme

Answer 6

Nine pairs of microtubules on the outside, generate the bending waves of the tail as adjacent pairs slide past one another in a coordinated movement
Two central fibrils

Question 7

Describe dyneins role in sperm motility

Answer 7

Allow fibrils to contract and relax
Switch inhibition mechanism: as one side of dyneins is inhibited the other is not
Dyneins ‘walk’ along the microtubules
Leads to bending motion

Question 8

Sperm motility indicates its… Where do sperm get their energy?

Answer 8

Metabolic state

Derived from substrates in the seminal fluid (fructose, sorbitol, GPC)

Question 9

How does energy availability affect sperm viability

Answer 9

When in the epididymus, no O2 or energy substrates are present and sperm is viable for days
After ejaculation, exposed to O2 and energy available, sperm is viable for hours (motility begins)

Question 10

What is sperm capacitation

Answer 10

Process whereby sperm acquire fertility through interactions with the female reproductive tract

Ejaculated sperm not yet able to fertilize oocyte; must be exposed to appropriate factors/environment, experience appropriate modifications

Question 11

What is added to sperm in the epididymus

Answer 11

Egg-binding proteins
Allow them to bind an oocyte

Question 12

What is coated on the heads of ejaculated sperm? What happens in the fem repro tract?

Answer 12

Coated with de-capacitation factors that mask egg-binding proteins
In the female tract, capacitation factors remove decapacitation factors which exposes egg-binding proteins so they can interact with oocyte to initiate fertilization

Question 13

Slide 14

Answer 13

Decapacitation + capacitation

Question 14

What happens during the acrosome reaction?

Answer 14

Sperm plasma membrane binds with outer acrosomal membrane
This allows for the release of acrosomal enzymes that allow the sperm to penetrate the oocyte zona pellucida

Slide 15

Question 15

Swine semen characteristics

Answer 15

High volume (bc of gel fraction)
Low proportion of motile sperm and normal sperm

Slide 16

Question 16

Macroscopic semen evaluations

Answer 16

• semen volume
• colour
• odour
• viscosity
• pH
• debris

Question 17

Microscopic semen evaluation

Answer 17

• motility
• morphology
• semen concentration (sperm/ml)

Question 18

Describe ‘motility’ microscopic evaluation of semen

Answer 18

• percent motile
• motility rating (rapid progression? slow? none?)
• motility patterns (linear progression? circular? rolling?)

Question 19

Describe ‘morphology’ microscopic semen evaluation

Answer 19

• percent normal
• percent abnormal

Question 20

Examples of abnormal sperm morphology

Answer 20

• amorphous
• tapered head
• double heat and/or tail
• bent head
• cytoplasmic droplets

Question 21

Slide 20, 21

Answer 21

Sperm morphology of diff species

Question 22

Slides 19, 22

Answer 22

Sperm abnormalities