Bio - low yield

What is the pathway sperm travels from creation to ejaculation?

Seminiferous tubules → Straight tubules (tubuli recti) → Rete testis → Efferent ductules → Epididymis → Vas deferens → Ejaculatory duct → Prostatic urethra → Membranous urethra → Spongy/penile urethra → Outside body

Where are sperm actually produced?

Inside the seminiferous tubules of the testes.

What are seminiferous tubules?

Highly coiled tubes inside the testes where spermatogenesis occurs.

What cells line the seminiferous tubules?

Spermatogenic cells (developing sperm) and Sertoli cells

What is located BETWEEN seminiferous tubules?

Interstitial tissue containing: leydig cells, blood vessels, and connective tissue

Where are Leydig cells located?

In the interstitial space between seminiferous tubules.

What do Leydig cells produce?

testosterone

What hormone stimulates Leydig cells?

LH

Support developing sperm cells by:

• Nourishing sperm

• Forming blood-testis barrier

• Producing inhibin

• Producing androgen-binding protein (ABP)

• Helping sperm mature

sertoli cells

What hormone stimulates Sertoli cells?

FSH

What does inhibin do?

Negative feedback on FSH release from anterior pituitary.

What does androgen-binding protein (ABP) do?

Keeps testosterone concentrated inside seminiferous tubules to support spermatogenesis.

What forms the blood-testis barrier?

Tight junctions between Sertoli cells.

Protects developing sperm from immune attack because sperm are genetically different from body cells after meiosis.

blood-testis barrier

What is the full pathway of spermatogenesis?

Spermatogonium → Primary spermatocyte → Secondary spermatocyte → Spermatid → Spermatozoa (mature sperm)

Which cells are diploid (2n) during spermatogenesis?

Spermatogonium and primary spermatocyte

• Secondary spermatocyte

• Spermatid

• Spermatozoa

are

haploid (n) during spermatogenesis

What does a spermatogonium do?

Stem cell that undergoes mitosis to produce primary spermatocytes.

Where are spermatogonia located?

Near the basement membrane of seminiferous tubules.

What happens to a primary spermatocyte?

Undergoes meiosis I → forms two secondary spermatocytes.

What happens to secondary spermatocytes?

Undergo meiosis II → form spermatids.

What process converts spermatids into mature sperm?

Spermiogenesis.

Spermatids transform into sperm by:

• Losing excess cytoplasm

• Developing flagellum

• Forming acrosome

• Condensing nucleus

• Packing mitochondria into midpiece

process of spermiogenesis

What is the acrosome?

Cap on sperm head containing enzymes used to penetrate egg.

What organelle forms the acrosome?

Golgi apparatus

Where are mitochondria concentrated in sperm?

midpiece

Why are mitochondria concentrated in the sperm midpiece?

Provide ATP for flagellar movement.

What are the three major parts of sperm?

head, piece, tail (flaggelum)

What is in the sperm head?

nucleus + acrosome

What is in the sperm midpiece?

mitochondria

What is the function of the sperm tail?

movement/propulsion

What happens in the epididymis?

Sperm: Mature, Gain motility, Are stored

Are sperm motile immediately after leaving seminiferous tubules?

No. They gain motility in the epididymis.

What is the function of the vas deferens?

Transports sperm from epididymis toward ejaculatory duct.

What type of muscle is abundant in vas deferens?

smooth muscle

What movement propels sperm through vas deferens?

peristalsis

What do seminal vesicles contribute to semen?

fructose, Prostaglandins, alkaline fluid

Why is fructose important in semen?

Provides energy source for sperm.

Why is semen alkaline?

Neutralizes acidic vaginal environment.

What percentage of semen comes from seminal vesicles?

~70%

What does PSA - prostate specific antigen do?

Liquefies semen after ejaculation

What do bulbourethral (Cowper) glands secrete?

pre-ejaculate mucus

Function of bulbourethral gland secretions?

lubrication + Neutralize acidic urine in urethra

What is the reproductive hormone pathway?

Hypothalamus → GnRH → Anterior pituitary → LH & FSH → Testes

What does LH do in males?

Stimulates Leydig cells → testosterone production.

What does FSH do in males?

Stimulates Sertoli cells → spermatogenesis support.

What hormone provides negative feedback to hypothalamus and pituitary?

testosterone

Why are testes located outside the body?

Spermatogenesis requires temperature slightly below body temperature.

What muscle wrinkles scrotal skin?

dartos muscle

What muscle raises testes closer to body?

cremaster muscle

What is the pathway of oogenesis?

Oogonium → Primary oocyte → Secondary oocyte → Ovum

When are females born, what stage are oocytes arrested in?

Primary oocytes arrested in prophase I.

When does a primary oocyte complete meiosis I?

right before ovulation

What is ovulated?

Secondary oocyte arrested in metaphase II

When does meiosis II finish?

only after fertiziliation

What cells surround developing oocytes?

granulosa cells

What do granulosa cells produce?

Estrogen (via aromatization).

What cells produce androgens in ovaries?

theca cells

What hormone stimulates theca cells?

LH

What hormone stimulates granulosa cells?

FSH

What structure forms after ovulation?

corpus luteum

What does the corpus luteum secrete?

Progesterone (and some estrogen).

What hormone causes ovulation?

LH surge

What hormone thickens the endometrium after ovulation?

progesterone

What phase occurs BEFORE ovulation?

follicular phase

What phase occurs AFTER ovulation?

luteal phase

Where does fertilization usually occur?

ampulla of fallopian tubes

What reaction allows sperm to penetrate egg?

Acrosomal reaction

What prevents polyspermy?

cortical reaction

Leydig cells make _____ while Sertoli cells support _____

Testosterone; spermatogenesis.

Seminiferous tubules make sperm while interstitial cells make

Testosterone.

Which reproductive cells are haploid?

Secondary spermatocytes onward.

Which male structure stores sperm?

epididymis

Which gland contributes most semen volume?

seminal vesicles

Sertoli =

support sperm

Leydig =

libido/testosterone

A cell has 46 chromosomes before S phase. After DNA replication, how many chromosomes does it have.

46 chromosomes. DNA replication doubles chromatids, NOT chromosome number.

After S phase, how many chromatids are present in a human somatic cell?

92 chromatids. 46 chromosomes × 2 sister chromatids each.

During metaphase of mitosis, how many chromosomes are present in a human cell?

46

During anaphase of mitosis, why does chromosome number temporarily double?

Sister chromatids separate and each becomes its own chromosome.

46 → 92 chromosomes temporarily.

At the END of mitosis, how many chromosomes are in each daughter cell?

46

What separates during meiosis I?

Homologous chromosomes. NOT sister chromatids.

What separates during meiosis II?

sister chromatids.

During meiosis I, does chromosome number change?

yes. diploid → haploid

Why is meiosis I called “reductional division”?

Because chromosome number is cut in half.

Why is meiosis II called “equational division”?

Because chromosome number stays the same.

At the end of meiosis I, are chromosomes still duplicated?

Yes. Each chromosome still has sister chromatids attached.

Are cells haploid after meiosis I?

yes, They are haploid BUT chromosomes are still duplicated.

A diploid cell before S phase is:

2n, 2c

A diploid cell after S phase is:

2n, 4c

A cell after meiosis I is:

1n, 2c

What does “c” represent?

Amount of DNA content.

What does “n” represent?

Number of chromosome sets (ploidy).

A cell after meiosis II is:

1n, 2c

Meoisis →

haploid - makes 4 cells

mitosis -

diploid, makes 2 cells

between what structures does crossing over occur?

Non-sister chromatids of homologous chromosomes.

Does crossing over occur between sister chromatids?

normally no Because sister chromatids are genetically identical.

during what stage does crossing over occur?

prophase I of meiosis.

What structure holds homologous chromosomes together during crossing over?

synaptonemal complex.