gameteogenesis and female cycles

Gametogenesis

Formation of gametes via meiosis

Diploid

2n, 46 chromosomes(23 pairs)

Haploid

1n, 23 chromosomes

homologous chromosomes

chromosomes that contain genes that code for the same traits

Mitosis

Process by which most body cells divide

only one round of division

produces 2 identical diploid daughter cells

provides cells for growth and repair

Meiosis

Process by which gametes are formed, two rounds of division, produces 4 haploid daughter cells

Meiosis Steps

Interphase

Prophase 1(m1)
Anaphase 1(m1)

Anaphase 2(m2)

Interphase

Cell grows and duplicates its DNA

Still 2n but has 92 chromatids

Prophase 1

tetrads form by synapsis of homologues

Chiasmata form

Anaphase 1

homologues separate

daughter cells of meiosis 1 produced

Anaphase 2

sister chromatids separate

4 gametes formed

Synapsis

side by side pairing of homologous chromosomes, forms small groups of 4 chromatids(tetrads)

Crossing over and Chiasmata

free ends of maternal and paternal chromatids cross over to exchange genetic material, allows for diversity

Spermatogenesis

process of sperm production in the seminiferous tubules, begins at puberty and continues through life

Spermatogenesis steps

Spermatogonial Stage

Primary Spermatocyte Stage
Secondary Spermatocyte Stage

Spermatid Stage

Spermatozoa Stage

Spermatogonial Stage

The spermatogonium(stem cell) undergoes mitosis,

daughter cell(primary spermatocyte) grows and moves to the adluminal compartment enters meiosis 1

Primary Spermatocyte stage

completes meiosis 1, forms 2 connected secondary spermatocytes

Secondary spermatocyte stage

Complete meiosis 2, forms 4 connected spermatids

Spermatid stage

grow from early spermatids to late spermatids with tail, still connected

Spermatozoa stage

separate and go to epididymis for maturation

division of spermatogenesis stages

Meiosis stages(spermatagonia-early spermatids)

Spermiogenesis(late spermatids-spermatozoa)

Spermatogenesis location progression

deep=>superficial

tubule periphery=>lumen

Sertoli cells(sustenocyte)

support and nourish the germ cells(developing sperm), form blood testis barrier

Oogenesis

process of producing an egg, produces one a month

Follicle development Stages

Primordial follicle

Primary follicle

Secondary follicle

Late secondary follicle

Vesicular(antral) follicle

Ruptured follicle

Corpus luteum

Corpus albicans

Primordial follicle

A primary oocyte surrounded by a single layer of squamous pre-granulosa cells, produced in the fetus and present from birth

Primary follicle

Begins at puberty, squamous pre-granulosa cells become cuboidal and surround the oocyte.

Secondary follicle

Pre-granulosa cells divide and form a stratified cuboidal epithelium around the primary oocyte. Pre-granulosa cells become granulosa cells.

late secondary follicle

The oocyte secretes a glycoprotein to form the zona pellucida. This membrane is now surrounded by theca folliculi, clear liquid has accumulated in between the granulosa cells.

Vesicular(antral) follicle

More Liquid accumulates between the granulosa cells and forms the antrum.

Corona radiata is formed

primary oocyte completes meiosis 1, forms secondary oocyte and a polar body

Ruptured follicle

follicle ruptures, secondary oocyte is released with its corona radiata into the uterine tubes

Meiosis 2(necessary to produce ovum) is only completed upon fertilization

Corpus luteum

The yellow body formed by granulosa cells from the ruptured follicle. Secretes estrogen and progesterone

Corpus albicans

the white body that represents further deterioration of the corpus luteum

Meiotic stages of the oocyte

Oogonium (2n)

Primary oocyte (2n)

Primary oocyte(arrested meiosis til puberty)

Secondary oocyte (n) + 1st polar body

Secondary oocyte(ovulated cell, meiosis arrested)

Ovum + 2nd polar body(if fertilized)

What process forms the primary oocyte(from oogonium)

mitosis

menstrual(uterine) cycle hormone control

controlled by hormones(estrogen and progesterone)

Menstrual cycle phases

Menstrual

Proliferative

Secretory

Menstrual

the functional layer of the endometrium is shed

Proliferative

The functional layer of the endometrium is rebuilt

Secretory

Begins immediately after ovulation.

Enrichment of blood supply and glandular secretion of nutrients prepare the endometrium to receive an embryo

Estrogen peak

during proliferative

Progesterone peak

secretory phase

when are dyads visible

Both mitosis and meiosis

when are tetrads visible

meiosis only

Prophase, metaphase, anaphase, and telophase presence

both in meiosis and mitosis

mitosis location

throughout the body

meiosis location

gonads(testes/ovaries) only

How does crossing over introduce variability in the daughter cells?

Allows for the mixing of maternal and paternal genes, leading to genetic diversity

Why are spermatids not functional gametes?

they are immature, non-motile cells that lack the specialized structures necessary for fertilization.

Differentiate spermatogenesis from spermiogenesis

Spermatogenesis - complete process of creating haploid spermatozoa

Spermiogenesis - final stage of spermatogenesis, where non-motile spermatids become motile spermatozoa

Primary oocytes and fetal development

By birth, all oogonia that will become oocytes have already completed their conversion

final products of spermatogenesis vs. oogenesis

S-four spermatozoa

O-ovum and 3 polar bodies

What is the function of the unequal cytoplasmic division observed during oogenesis?

ensures the mature ovum retains nearly all the cytoplasm, nutrients, and organelles needed for early embryonic development.

What is the fate of the polar bodies and why do they receive this fate?

Polar bodies degenerate and are reabsorbed (undergo apoptosis) in the ovary.

Done to discard extra chromosomes while preserving the cytoplasm in one cell.

Endometriosis occurs when fragments of endometrial tissue undergo retrograde menstruation, resulting in displaced tissue that often attaches to the peritoneum of the pelvic cavity. These fragments respond to hormonal changes, resulting in bouts of severe pain after menstruation has ended. Explain how the female anatomy contributes to the ability of this tissue to relocate and attach to the peritoneum.

The female reproductive tract is open to the peritoneal cavity through the fallopian tubes, if endometrial tissue flows backwards into the cavity, it can implant on the peritoneum and continue responding to hormones.

Natural family planning, or fertility awareness is a method that can be used to achieve or prevent pregnancy. It is based on the ability to predict ovulation. Measuring which hormone would be the best predictor for ovulation and why?

LH, shows a rapid large surge before ovulation

ovulation follows this surge about 24-36 hours this after this peak