Lesson 1: Reproductive Systems

Male reproductive system

Further functions

Urethra: tube from ejaculatory duct through penis that carries semen and urine (but not at the same time)

Prostate: also neutralizes acidity of vagina Bulbourethral gland: also “cleans out”

urethra, releases fluid before ejaculation, contributes to unplanned pregnancies

Sperm make only a small part of semen; 90+% of volume from seminal vesicles

1.Mitosis makes enough cells from spermatogonium to keep the same number and produce sperm2.Primary spermatocytes grow3.Cells divide through the two divisions of meiosis (secondary spermatocytes)4.Cells (spermatids) differentiate as they developSertoli cells support developing sperm.

(germinal epithelium)

(spermatozoa)

(produce testosterone)

(nurse cell)

Structure of a Mature Sperm (50 um)

Acrosome: chemicals to enter egg

Nucleus: haploid Midpiece: “motor”, many

mitochondria Flagellum: protein, 9+2

microtubule pattern Flagellum ~40 um

Hormonal Control of Spermatogenesis

Luteinizing hormone (LH): increases testosterone levels

Follicle Stimulating hormone (FSH): controls meiosis / number of sperm

Testosterone: helps sperm production and development

* FSH and LH named for role in females (menstrual cycle)

Secondary sexual characteristics

Related to sexual development, but not necessary for reproduction

Development occurs during puberty

Roles of Testosterone in Males Gonads become either

testes or ovaries (ovary is default)

Gene on Y chromosome (when fetus is in week 7) shifts gonads to testes

Testes release testosterone Testosterone leads to

development of secondary sexual characteristics at puberty

Production of sperm Maintenance of sex drive

Timing and Number of Sperm Production

Begins at puberty, continues until death Continually produced, millions each day Complete process takes several months One diploid cell produces 4 haploid sperm

with equal amounts of cytoplasm May be released voluntarily

1

2

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4

6

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89

10

11

5

1. Ureter2. Urinary

bladder3. Seminal

vesicle4. Prostate5. Bulbourethr

al gland6. Vas

deferens (ductus deferens)

7. Epididymis8. Scrotum9. Testes10.Urethra11.Penis

(holds fetus in uterus)

(site of fertilization)

(for urination)

All follicles present at birth (one primary oocyte each)

Follicle stimulating hormone (FSH) causes some follicles to develop; usually one per month will mature

The follicle stays in the same place in the ovary

The mature, large, fluid- filled follicle seen before ovulation is called a Graafian follicle.

After ovulation, the follicle becomes the corpus luteum

Mature (Graafian)

follicle

unequal division of cytoplasm

A secondary oocyte is released to the fallopian tubes (oviduct) in ovulation

When triggered by the arrival of a sperm, meiosis will finally be completed, releasing the second polar body.

(also called yolk, contains lipid droplets)

(and centrioles)for

first

Haploid DNA in metaphase II

Estrogen and progesterone are major female hormones. They cause Pre-natal (embryonic/fetal) development of

female sex organs Development of secondary sexual

characteristic during puberty

Timing and Number of Ova Production

All eggs begin meiosis during fetal development

At puberty, ~1 egg / month continues meiosis, release time hormonally controlled (menstrual cycle)

Meiosis only completed if sperm enters egg

Unequal division of cytoplasm; one diploid cell produces one ovum and 2-3 polar bodies

Compare oogenesis and spermatogenesis.

Spermatogenesis v. Oogenesis In testes

Millions produced continually (after puberty); released as needed / voluntary control

Four motile sperm produced per meiosis (equal cytoplasm)

Meiosis begins (primarily) in puberty

Sperm made indefinitely Requires testosterone

and Sertoli (nurse) cells

In ovaries One oocyte released per

month long cycle, hormonal control

One egg per meiosis (+2-3 small polar bodies) with unequal division of cytoplasm

Meiosis begins during fetal stage, none in childhood, completed after puberty (when sperm present)

Viable egg supply gone by menopauseSimilarities include: mitosis in germ cells, cell growth before meiosis,

two divisions of meiosis, haploid nuclei, need for LH and FSH, etc.

1. Uterus2. Fallopian

tube (oviduct)

3. (Fimbriae)4. Ligament5. Cervix6. Vagina7. Endometriu

m8. Ovary9. Urinary

bladder10.Urethra11.Pelvic bone12.Clitoris13.Labia14.Urethral

orifice15.Intestine16.Anus