13.8: Overview of the Human Reproductive System
- Page ID
- 121765
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\( \newcommand{\dsum}{\displaystyle\sum\limits} \)
\( \newcommand{\dint}{\displaystyle\int\limits} \)
\( \newcommand{\dlim}{\displaystyle\lim\limits} \)
\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)
( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\id}{\mathrm{id}}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\kernel}{\mathrm{null}\,}\)
\( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\)
\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\)
\( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)
\( \newcommand{\vectorA}[1]{\vec{#1}} % arrow\)
\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}} % arrow\)
\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vectorC}[1]{\textbf{#1}} \)
\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)
\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)
\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\(\newcommand{\longvect}{\overrightarrow}\)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The reproductive system produces gametes, supports fertilization and pregnancy, and enables the development and birth of a new individual.
- Describe the major structures and functions of the male and female reproductive systems.
- Distinguish diploid and haploid cells by chromosome number and explain why haploid gametes are necessary.
- Compare mitosis and meiosis.
Understanding the Language of Biological Sex in Anatomy and Physiology
When you study Anatomy and Physiology, you will often encounter descriptions of how structures and processes differ between the biological sexes. In everyday language, the words “female” and “male” may refer either to gender identity or to biological sex. In science, however, these terms refer specifically to biological sex, which is determined by chromosomes, hormones, and reproductive anatomy. Gender identity is a separate concept related to how a person experiences and identifies themselves, and it may or may not align with the sex assigned at birth.
In this course, the terms female and male refer only to biological sex and to the typical anatomy and physiology associated with XX (female) and XY (male) chromosomal patterns.
The Role of the Reproductive System
The reproductive system enables the production of offspring and supports the biological processes required for fertilization, pregnancy, and birth. It includes sets of paired or complementary organs in biological males and females, and its functions are coordinated by multiple hormones. In humans, reproduction occurs through internal fertilization: sperm enter the female reproductive tract and may unite with an ovum, forming a zygote that begins development into an embryo and eventually a fetus.
Major Structures of the Male and Female Reproductive Systems
In this section, you will explore the structures and functions of the male and female reproductive systems and discover how healthy coordination between these systems can culminate in the powerful sound of a newborn’s first cry.
Before diving into the details, let's cover some basic common terms. Unique for its role in human reproduction, a gamete is a specialized sex cell carrying 23 chromosomes — one half the number found in other body cells. Gonads are the organs that make the gametes. Once the gametes are made, they travel in tubular structures. These structures are often the site for permanent sterilization procedures because if the gametes of the opposite sex cannot meet, then fertilization will not be possible. Comparing the midsagittal view of the female and male pelvis, there are multiple differences (See figures below). We will first start with the discussions on the male reproductive system, then move to the female.
| Term | Male | Female |
|---|---|---|
| Gonads | Testes | Ovaries |
| Gametes | Sperm | Ova (ovum, singular, also known as eggs) |
| Tract Organs | Ductus deferens (or vas deferens), ejaculatory duct, urethra | Uterine tubes (or Fallopian tubes), uterus, vagina |
| Permanent Sterilization Procedure | Vasectomy | Tubal ligation, hysterectomy |
| Copulatory organ | Penis | Vagina |
Sexual maturity begins with puberty, when the reproductive organs start producing gametes.
Male Reproductive System
The human male reproductive system consists of internal and external organs located in and around the pelvic region. Its primary biological function is to produce, store, and deliver sperm for potential fertilization of an ovum. The organs can be grouped into three functional categories:
Sperm Production and Storage
-
Spermatogenesis occurs in the seminiferous tubules of the testes. The testes produce both sperm (male gametes) and testosterone.
-
Epididymis: A long, coiled tube where sperm mature and are stored until ejaculation.
Accessory Glands
The accessory glands produce the fluids that support and transport sperm. Semen is the combination of these fluids with sperm. Specifically, these glands produce fluids that:
- protect sperm from the acidic environment of the urethra and vagina
- provide nutrients that help sperm survive and function
- supply the bulk of the liquid that carries sperm through the male reproductive tract
- help sperm move more easily by reducing friction and thickening or thinning the fluid as needed.
The three accessory glands are the
-
Seminal vesicles: produce a thick, nutrient-rich fluid that makes up most of the semen and helps energize sperm.
-
Prostate gland: adds a thin, slightly alkaline fluid that protects sperm and helps them move more easily through the female reproductive tract.
-
Bulbourethral (Cowper’s) glands: release a small amount of clear, slippery fluid that lubricates the urethra and helps neutralize any leftover acidity before sperm pass through.
Structures for Sperm Transport
-
Vas deferens: Transports sperm from the epididymis toward the urethra.
-
Urethra: Passageway for semen during ejaculation; also part of the urinary system.
-
Penis: External organ that delivers sperm (in the form of semen) into the female reproductive tract. It contains erectile tissues that fill with blood during sexual arousal.
Female Reproductive System
The human female reproductive system includes a set of internal organs in the pelvic cavity and external structures at the vulva. The external opening leads into the vagina, a muscular canal that receives semen during intercourse. It also functions as the birth canal during delivery and provides the passageway for menstrual flow. Mucus from the Bartholin's glands helps lubricate this area.
The vagina leads to the cervix, the lower, narrow portion of the uterus that opens into the vagina. The uterus is a muscular organ that houses and supports a developing fetus during pregnancy.
Ovum Production and Transport
On each side of the uterus lie the ovaries, the organs responsible for producing the female gametes. This process, called oogenesis, is the female equivalent of spermatogenesis in males. Oogenesis begins before birth, pauses, and then resumes at puberty, continuing across the reproductive lifespan. The mature ovum, like a sperm cell, is haploid, meaning it carries only one set of chromosomes.
Besides producing the ova (eggs), the ovaries also produce the hormones estrogen and progesterone. Each month, an ovary typically releases one ovum. The ovum enters a Fallopian tube, where fertilization commonly occurs if sperm are present.
If a sperm fertilizes the ovum, the resulting zygote begins dividing as it travels to the uterus, where a fertilized egg implants in the endometrium and pregnancy begins with embryonic development.
If fertilization does not occur, the thickened endometrium is not needed, so it breaks down and is shed along with the unfertilized ovum during menstruation, the monthly cycle.
Diploid and Haploid: Understanding Chromosome Count
Chromosomes are long, tightly coiled strands of DNA that organize and store the genetic information inside each cell.
Humans normally have 46 chromosomes arranged in 23 pairs, with one chromosome in each pair inherited from the mother and the other from the father. Along the length of each chromosome are thousands of genes, which are small segments of DNA that function like individual instructions for building proteins and guiding the body’s development and activities.
The somatic cells in the human body contain 46 chromosomes — the full diploid number — meaning they have two sets of chromosomes. Diploid cells include skin cells, liver cells, muscle cells, nerve cells, and all the other cells that make up the body.
Alternatively, gametes — specifically, the sperm and egg cells — contain only 23 chromosomes. This reduced haploid number allows fertilization to restore the complete set of 46 chromosomes in the zygote, keeping the chromosome number stable from one generation to the next.
Why Does This Matter?
Mitosis and meiosis are the two major ways cells divide in the human body.
Mitosis is the type of cell division used for growth, repair, and everyday maintenance, producing two genetically identical diploid cells.
Meiosis is different because it is used only to make gametes; it involves two rounds of division and produces four genetically unique haploid cells.
In short, mitosis makes identical body cells, while meiosis creates specialized sex cells with half the usual chromosome number. Keeping chromosome numbers consistent from generation to generation is critical as it prevents cells from gaining too much DNA. Meiosis, the special cell division that makes gametes, cuts the chromosome number in half so that fertilization can restore it to the normal diploid number.
Fertilization and Early Development
Fertilization occurs when a paternal sperm nucleus fuses with a maternal egg nucleus to form the first cell of a new individual: the zygote.
-
The zygote is diploid (2n), containing 46 chromosomes again, one set of 23 chromosomes from each parent.
-
After fertilization, the zygote undergoes rapid mitotic divisions and cell differentiation, forming an embryo during the first 8 weeks of development.
-
After 8 weeks, the developing human is considered a fetus, which continues growing until birth at approximately 40 weeks of gestation.
This entire sequence, beginning from a single microscopic zygote, highlights why gametes must be haploid: combining two half-sets of chromosomes ensures that the species maintains a consistent chromosome number.
Figure \(\PageIndex{6}\): Fertilization. Fertilization occurs when sperm that have traveled through the uterus enter a Fallopian tube and encounter an ovulated egg. The ovary releases the mature oocyte during ovulation, and the egg is then moved along the tube where fertilization commonly takes place. The inset highlights the moment a sperm reaches and fuses with the egg, beginning the formation of a zygote.