Intake, elimination & reproduction · Topic 18 of 18

Reproductive System

Male Reproductive System

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A&P · reproductive system

Male Reproductive System

The testes make sperm and testosterone; a chain of ducts carries sperm out while three glands add the fluid that becomes semen.

01 · GonadsTestes make sperm and testosterone

02 · Sperm pathTestis → epididymis → vas deferens → urethra

03 · HormoneTestosterone → sperm + male sex traits

What it is

Scrotum keeps testes 2–4 °C cooler than the core — sperm need it

Semen = sperm + fluid from 3 glands; sperm are only ~5% of it

Parts & jobs

Testes (male gonads): make sperm and testosterone must know

Epididymis: sperm mature, learn to swim and are stored must know

Seminiferous tubules (inside the testis) = where sperm are made

Vas deferens: muscular tube from epididymis to behind the bladder

Seminal vesicles: ~60% of semen; fructose fuels the sperm

Prostate: wraps the urethra below the bladder; adds alkaline fluid

Bulbourethral (Cowper's) glands: pre-ejaculate lubricates and clears the urethra

Male urethra carries both urine and semen out through the penis

Sperm: head (DNA + acrosome), midpiece (mitochondria), tail (flagellum)

Step by step

Sperm path: testis → epididymis → vas deferens → ejaculatory duct → urethra

Spermatogenesis: 1 primary spermatocyte → 4 haploid sperm (puberty onward)

The rules

Testosterone: drives sperm production and male secondary sex traits must know

In males: LH → testosterone (Leydig); FSH → sperm production (Sertoli)

Don't confuse

Sertoli cells nurse sperm; Leydig cells make testosterone

Sertoli cells or Leydig cells?

Commonly confused

	Sertoli cells	Leydig (interstitial) cells
Where	Inside the seminiferous tubules	Between the tubules
Job	Support and nourish developing sperm	Make testosterone
Pituitary hormone that drives it	FSH	LH

Mix-ups to avoid

Made in the seminiferous tubules ≠ matured in the epididymis

More detail

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GnRH → LH/FSH; testosterone and inhibin feed back to turn them down

~64 days per sperm cycle; ~100–300 million sperm made per day

Cold: dartos and cremaster pull testes up; warmth: scrotum relaxes

Testes descend ~7th fetal month; undescended testis = cryptorchidism

Penis: 2 corpora cavernosa + corpus spongiosum; erection = blood filling

Pearl

Made in the seminiferous tubules, matured in the epididymis, mixed into semen on the way out.

Sources · OpenStax Anatomy & Physiology 2e §27.1 Anatomy and Physiology of the Testicular Reproductive System · OpenStax Anatomy & Physiology 2e §28.1 Fertilization · Union Test Prep — HESI Anatomy & Physiology study guide, page 4 (reproductive system) · Union Test Prep — HESI Anatomy & Physiology study guide, page 2 (endocrine system) · Built from the verified NurseSavvy HESI A2 fact map (facts reviewed 2026-10-16). HESI is a trademark of Elsevier; NurseSavvy is not affiliated with Elsevier.

Female Reproductive System & Menstrual Cycle

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A&P · reproductive system

Female Reproductive System & Menstrual Cycle

The ovaries make eggs and hormones; each cycle estrogen builds the uterine lining, an LH surge releases the egg, and progesterone keeps the lining ready.

01 · Timing28-day cycle, ovulation ≈ day 14

02 · OvulationLH surge → ovulation

03 · Lining hormonesEstrogen builds, progesterone keeps the lining

Parts & jobs

Ovaries (female gonads): make eggs, estrogen and progesterone must know

Uterus: where the embryo grows; its lining (endometrium) builds and sheds must know

Uterine (fallopian) tubes: carry the egg from ovary to uterus

Fimbriae sweep the egg in; cilia and muscle move it along the tube

Uterine wall: endometrium (lining), myometrium (muscle), perimetrium (outer)

Cervix: neck of the uterus into the vagina; dilates in labor

Vagina: receives sperm, outlet for menses, birth canal

Menstrual (uterine) cycle

Step by step

Menses (≈ days 1–5): progesterone falls, the lining sheds

Proliferative (to ≈ day 14): estrogen regrows the lining

Secretory (≈ days 15–28): progesterone readies the lining for implantation

Ovarian cycle

Step by step

Follicular phase: FSH grows follicles, which secrete estrogen

Luteal phase: empty follicle → corpus luteum → progesterone

No pregnancy: corpus luteum dies, hormones fall, menses starts again

Know by heart

28-day cycle: day 1 = first day of bleeding; ovulation ≈ day 14 must know

The rules

LH surge triggers ovulation (release of the egg) must know

Estrogen builds the lining; progesterone maintains it must know

Don't confuse

Oogenesis: 1 egg + polar bodies (vs 4 sperm per spermatocyte)

Ovarian cycle or menstrual (uterine) cycle?

Commonly confused

	Ovarian cycle	Menstrual (uterine) cycle
What changes	Follicles and the egg in the ovary	The endometrium lining the uterus
Before ovulation	Follicular phase (FSH grows follicles)	Menses, then proliferative phase
After ovulation	Luteal phase (corpus luteum)	Secretory phase
Main hormone, first half	Estrogen from the growing follicles	Estrogen rebuilds the lining
Main hormone, second half	Progesterone from the corpus luteum	Progesterone readies the lining

Mix-ups to avoid

FSH grows the follicle; LH releases the egg — don't swap them

More detail

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Oocytes form before birth, pause in meiosis I; finish only if fertilized

Oocytes: ~1–2 million at birth → ~400,000 at puberty → 0 at menopause

Very high estrogen → positive feedback → LH surge

Menopause: follicles run out; no period for 12 months, ≈ age 50–52

Breasts: accessory organs; mammary glands (modified sweat glands) make milk

Vulva = mons pubis, labia majora and minora, clitoris

Pearl

Estrogen builds the lining, LH releases the egg, progesterone holds the lining; when progesterone drops, the lining sheds.

Sources · OpenStax Anatomy & Physiology 2e §27.2 Anatomy and Physiology of the Ovarian Reproductive System · OpenStax Anatomy & Physiology 2e §27.1 Anatomy and Physiology of the Testicular Reproductive System · Union Test Prep — HESI Anatomy & Physiology study guide, page 4 (reproductive system) · Built from the verified NurseSavvy HESI A2 fact map (facts reviewed 2026-10-16). HESI is a trademark of Elsevier; NurseSavvy is not affiliated with Elsevier.

Fertilization, Pregnancy & Population Factors

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A&P · reproduction and populations

Fertilization, Pregnancy & Population Factors

Sperm and egg fuse in the uterine tube to form a zygote that implants in the endometrium; a population changes by births, deaths and migration.

01 · FertilizationSperm 23 + egg 23 = zygote 46

02 · WhereFertilized in the uterine tube

03 · PopulationBirths + immigration − deaths − emigration

What it is

Fertilization: sperm (23) + egg (23) → diploid zygote (46) must know

Birth rate and death rate are counted per 1,000 people per year

Fertility rate = average children per woman; ~2.1 = replacement level

Lower fertility: women's education, later marriage, family planning, fewer child deaths

Parts & jobs

Fertilization happens in the uterine (fallopian) tube, not the uterus must know

Placenta: O₂ and nutrients in, CO₂ and wastes out, makes hormones; bloods don't mix

Step by step

Implantation: the blastocyst embeds in the endometrium (~1 week)

Early development

Step by step

Zygote divides (cleavage) → morula (~16 cells) by ~day 3

Blastocyst: inner cell mass → embryo; trophoblast → placenta

Know by heart

Population change = (births + immigration) − (deaths + emigration) must know

Embryo = weeks 3–8 (organs form); fetus = week 9 to birth

Pregnancy ≈ 40 weeks from the last period; 3 trimesters of ~13 weeks

The rules

hCG keeps the corpus luteum making progesterone; pregnancy tests detect it

Oxytocin drives labor contractions — a positive feedback loop

Population change

(120 + 30) − (70 + 50) = +30 people; 30 ÷ 8,000 = 0.375% growth

(60 + 25) − (95 + 15) = −25 → the population declines

Don't confuse

Immigration = moving in (adds); emigration = moving out (subtracts)

Embryo or fetus?

Commonly confused

	Embryo	Fetus
When	Weeks 3–8 after fertilization	Week 9 until birth
What happens	Every organ system starts to form	Organs grow and mature
Came before it	Zygote, then blastocyst (weeks 1–2)	The embryo

Mix-ups to avoid

Umbilical vein (1) = O₂-rich to the fetus; arteries (2) = O₂-poor back

More detail

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Zero population growth: births + immigration = deaths + emigration

Demographic transition: deaths fall first, then births, until both are low

Wide-based age pyramid = fast growth; even, column-like = slow or none

Sperm survive ~3–5 days; the egg only ~24 hours after ovulation

Fraternal twins = 2 eggs + 2 sperm; identical = 1 zygote that splits

Amnion: fluid-filled sac that cushions and protects the fetus

Labor stages: cervix dilates to 10 cm → baby delivered → placenta (afterbirth)

Pearl

Births and immigrants add people; deaths and emigrants take them away.

Sources · OpenStax Anatomy & Physiology 2e §28.1 Fertilization · OpenStax Anatomy & Physiology 2e §28.2 Embryonic Development · OpenStax Anatomy & Physiology 2e §28.4 Changes During Pregnancy, Labor, and Birth · OpenStax Introduction to Sociology 3e §20.1 Demography and Population · Population Education — What factors affect the total fertility rate (TFR)? · United Nations — Global Issues: Population (replacement fertility ≈ 2.1 children per woman) · OpenStax Biology 2e §45.5 Human Population Growth · Population Reference Bureau — Glossary of demographic terms (balancing equation, birth rate, total fertility rate, zero population growth) · OpenStax Anatomy & Physiology 2e §27.1 Anatomy and Physiology of the Testicular Reproductive System · OpenStax Anatomy & Physiology 2e §27.2 Anatomy and Physiology of the Ovarian Reproductive System · Union Test Prep — HESI Anatomy & Physiology study guide, page 4 (reproductive system) · TSTC Library — HESI A2 guide (A&P content list: population growth and decline; birth and fertility rate factors) · Union Test Prep — HESI Anatomy & Physiology study guide, page 2 (endocrine system) · Built from the verified NurseSavvy HESI A2 fact map (facts reviewed 2026-10-16). HESI is a trademark of Elsevier; NurseSavvy is not affiliated with Elsevier.

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