2.1 Fertilization & Implantation

Physiologic process: The rupture of the dominant follicle of the ovary

Ovulation

Ovulation: Phases

Follicular phase

Luteal phase

Menstrual phase

Proliferative phase

Secretory phase

Ovulation: Phases that occur in the ovaries

Follicular phase

Luteal phase

Ovulation: Phases that occur in the endometrium

Menstrual phase

Proliferative phase

Follicular phase: __ stimulates follicle growth

FSH

What phase: __: Stimulates the development of 3 to 30 primordial follicles into primary follicles within the ovaries

Follicular phase

What phase: __: Estrogen levels

Follicular phase

What phase: __: Follicular atresia

Follicular phase

What phase: __: Estrogen levels increase, inhibiting FSH & causing stimulated follicles to degenerate

Follicular phase

What phase: __: Only one follicle becomes dominant and continues to mature

Follicular phase

What phase: __: Endometrial proliferation

Proliferative phase

What phase: __: Estrogen stimulates thickening of uterine lining

Proliferative phase

What phase: __: Cervical mucus is thinner and more elastic to facilitate sperm entry

Follicular phase

Ovulation: A surge in __ causes the mature dominant follicle to rupture and release the egg (ovulation)

LH

Ovulation: The egg is released around day __ in a typical __ cycle

14

28

Ovulation: Ruptured follicle transforms to __ which produces progesterone

Corpus luteus

What phase: __: Corpus luteum formation, progesterone dominance

Luteal phase

The release of a mature secondary oocyte from the ovarian follicle

Ovulation

Ovulation: Triggered by a surge in __

Luteinizing hormone

Ovulation: The oocyte is surrounded by the __ and __

Zona pellucida

Corona radiata

Ovulation: Viable for fertilization for about __ hours through the __ (area)

12-24

Fallopian tube

What phase: Corpus luteum forms then degenerates

Luteal phase

Egg: Oocyte:

• Size

• Shape

• Motile/Nonmotile

• Arrested stage

• Large (100μm)

• Symmetrical

• Nonmotile

• Metaphase 2 of meiosis (completed upon fertilization)

Oocyte: Glycoprotein coat acting as a barrier to the sperm

Zona pellucida.

Oocyte: Covered by __ layers

3

Egg: __ follicle

Graafian follicle

Egg: Layers

Corona radiata

Zona pellucida

Cumulus

Antrum

Theca layer

• Theca interna

• Theca externa

Egg: Layers: __: Innermost layer of cumulus, provides vital proteins to the oocyte

Corona radiata

Egg: Layers: __: Surrounds the oocyte

Zona pellucida

Egg: Layers: __: Found between the oocyte and follicular cell

Zona pellucida

Egg: Layers: __: Thin glycoproteins that help prevent polyspermy by binding to sperm preventing them to penetrate too deeply into the oocyte

Zona pellucida

Egg: Layers: __: Cluster of cells that surround the oocyte

Cumulus

Egg: Layers: __: Fluid filled space that develops among follicle cells

Antrum

Egg: Layers: __: Produces hormone (estrogen)

Theca interna

Egg: Layers: __: More of a connective tissue

Theca externa

Sperm

• Size

• Shape

• Motile/Nonmotile

• Components

• Small

• Asymmetrical

• Motile

• Head with acrosome, Mid piece, Tail

Sperm: Part of sperm that contains hydrolases

Head with acrosome

Sperm: Part: __: Contains nucleus

Head

Sperm: Part: __: Holds genetic material from father (DNA)

Head

Sperm: Part: __: 5-6 micrometers

Head

Sperm: Head: __: end of head

Cap (acrosome)

Sperm: Head: __: Contains enzymes that break down the outer membrane of the egg cell

Cap (acrosome)

Sperm: Head: __: Narrow region between head and tail

Neck

Sperm: Part: __: Region between head and tail

Midpiece

Sperm: Part: __: Contains mitochondria to provide energy for sperm mvt

Midpiece

Sperm: Part: __: Flagellum

Tail

Sperm: Part: __: Long whip-like structure (40-50 micrometers)

Tail

Sperm: Part: __: Helps propel through the reproductive tract

Tail

Process by which the secondary spermatocyte and secondary oocyte fuse

Fertilization

Where does fertilization occur

Ampullary region of the uterine tube

How many spermatozoas are deposited in the vagina during intercourse

2-5 million

Life span of sperm in female reproductive tract

3-7 days (ave 5 days)

Why is the sperm subject to physical stress

• Ejaculation

• Contractions in female tract

• Change in pH environment

• Mucous secretions

• Defenses of female immune system

• ANatomy of the fallopian tube (double tract fallopian tube)

When do sperm become motile again

Ovulation

At ovulation, sperm again become motile, perhaps because of __ produced by cumulus cells surrounding the egg, and swim to the __ where fertilization usually occurs

Chemoattractants

Ampulla

Can spermatozoa fertilize the oocyte immediately upon arrival in the female genital tract

NO

• Must undergo changes

Changes that happen to the spermatozoa to be able to fertilize the oocyte

• Capacitation

• Acrosome reaction

How many sperms enter the egg

only 1

What happens to the other sperms that try to enter the egg (but fail bc one alr entered)

Disintegrate d/t the 3 barriers around the oocyte

Disintegration of sperm is via __

hyaluronidase

3 barriers that prevent sperm from entering

• Corona radiata

• Zona pellucida

• Cortical reaction

Journey of sperm

Vagina → Cervix → Uterus → Fallopian Tube

Sperm transport: Out of the millions of sperm released, how many reach the egg

Few hundred

__: Sperm undergo maturation to become capable of fertilization

Sperm capacitation

Where and how does sperm capacitation occur

Through physiological changes in the female reproductive tract

Sperm capacitation: Processes

• Glycoprotein removal

• Membrane fluidity increased

• Hyperactivation

• Acrosome reaction

Sperm capacitation: Processes: __: Removes the glycoprotein layer from the sperm head to bind with the egg

Glycoprotein removal

Sperm capacitation: Processes: __: Sperm membrane is more fluid allowing better mobility

Membrane fluidity increased

Sperm capacitation: Processes: __: Enhances sperm mvt enabling them to reach egg faster

Hyper activation

Sperm capacitation: Processes: __: Release of enzymes that allow sperm to penetrate the egg’s outer layer

Acrosome reaction

Oocyte transport: Drawn into the fallopian tube by __

Fimbriae and cilia

Oocyte transport: Fallopian tube → __ (moves toward the __)

Uterus

Egg’s defenses: __: Outer layer of follicular cells

Corona radiata

Egg’s defenses: __: Glycoprotein layer surrounding the egg

Zona pellucida

Egg’s defenses: __: Once one sperm enters, the egg changes to prevent other sperm from entering

Cortical reaction

Egg’s defenses: __: Block to polyspermy

Cortical reaction

Egg’s defenses: __: Outermost layer of the egg

Corona radiata

Egg’s defenses: __: Composed of follicular cells

Corona radiata

Egg’s defenses: __: Protection and nourishment to the ovum

Corona radiata

Egg’s defenses: __: Facilitates the interaction bw sperm and egg

Corona radiata

Egg’s defenses: Corona radiata: Sperm must first penetrate through the __ to reach the iner layers of the egg

Corona radiata

Egg’s defenses: Corona radiata: Penetration utilizes enzymes including __ located in the acrosome of the sperm head

Hyaluronidase

Egg’s defenses: __: Thick, transparent membrane made of glycoproteins

Zona pellucida

Egg’s defenses: __: Made of glycoproteins found inside the __ before the plasma membrane

Zona pellucida

Corona radiata

Egg’s defenses: __: Serves a sa protective barrier and contains sperm binding receptors, allowing only one sperm to penetrate

Zona pellucida

Egg’s defenses: __: Main function is to prevent polyspermy

Cortical reaction

Egg’s defenses: Cortical reaction: Process

1. Sperm fuses with the egg

2. Specialized cortical granules released

3. Altered glycoproteins of the zona pellucida

4. "Zipping up" → barrier

5. Cant bind to zona pellucida or fuse with egg

Egg’s defenses: Cortical reaction: Location of specialized cortical granules

Under the egg’s plasma membrane

Egg’s defenses: Cortical reaction: Where are the specialized cortical granules released

Into the space bw the plasma membrane and zona pellucida

Key Stages of Penetration:

1. Penetration of corona radiata

2. Penetration of zona pellucida

3. Fusion of cell membranes

Key Stages of Penetration: __: Sperms flagellar or whipping action push the cells through

Corona radiata

Key Stages of Penetration: Corona radiata: __ (enzyme) breaks down __ (a major component of extracellular matrix of corona radiata)

Hyaluronidase

Hyaluronic acid

Key Stages of Penetration: __: Binding to ZP3 receptors

Penetration of zona pellucida

Key Stages of Penetration: __: Acrosome reaction

Penetration of zona pellucida

Key Stages of Penetration: __: Binding triggers release of digestive enzymes from the head (__) to digest the zona

Penetration of zona pellucida

Acrosin

Key Stages of Penetration: __: Enzyme reaction are released to digest zona pellucida and weakens the barrier

Penetration of zona pellucida

Key Stages of Penetration: __: Only 1 sperm successfully penetrates

Penetration of zona pellucida

Key Stages of Penetration: __: Sperm head and tail enter the oocyte cytoplasm

Fusion of cell membranes

Key Stages of Penetration: __: Plasma membrane of sperm fuses with membrane of oocyte

Fusion of cell membranes

Key Stages of Penetration: Fusion of cell membranes: What completes fertilization

Sperm’s head and tail entering the oocyte’s cytoplasm