Reproductive Systems
Chapter 21
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1
Learning Objectives
Lesson 21.1: Reproductive Systems
1.
2.
3.
List the essential and accessory organs of
the male and female reproductive systems
and give the general function of each.
Describe the gross and microscopic structure
of the gonads in both sexes and explain the
developmental steps in spermatogenesis
and oogenesis.
Discuss the primary functions of the sex
hormones and identify the cell type or
structure responsible for their secretion.
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2
Learning Objectives
Lesson 21.1. Reproductive Systems (Cont.)
4.
5.
Identify and describe the structures that
constitute the external genitals in both sexes.
Identify and discuss the phases of the
endometrial or menstrual cycle and correlate
each phase with its occurrence in a typical
28-day cycle.
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3
Sexual Reproduction

Producing offspring

Sexual reproduction requires two parent organisms,
a male and a female
•
•
Advantage: New mixture of genes in each offspring
increases the variety of genetic characteristics in the
population
Reproductive system of each parent produces the sex or
reproductive cells (called gametes)



Ovum (female); sperm (male)
Asexual reproduction requires only one parent
Sexual maturity and the ability to reproduce occur at
puberty
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Sexual Reproduction (Cont.)

Male and female systems



Common general structure and function can be
identified between the systems in both sexes
Systems adapted for development of sperm
or ova followed by successful fertilization,
development, and birth of offspring
Sex hormones in both genders is important in
development of secondary sexual characteristics
and normal reproductive system activity
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5
Male Reproductive System

Structural plan

Essential organs of reproduction
•

Gonads (testes), which produce sex cells (sperm or
spermatozoa)
Accessory organs of reproduction
•
Ducts

•
Sex glands

•
Passageways that carry sperm from testes to exterior
Produce protective and nutrient solution for sperm
External genitals
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6
Organization of the
Male Reproductive Organs
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Male Reproductive System (Cont.)

Testes: Gonads of men

Structure and location
•
Testes in scrotum

•
•
Lower temperature
Covered by tunica albuginea, which divides testis into
lobules containing seminiferous tubules
Interstitial cells produce testosterone
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8
Tubules of the Testis and Epididymis
Lennart Nilsson, Albert Bonnier Forlag A, Stockholm, Sweden.
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9
Male Reproductive System (Cont.)

Testes

Testis functions
•
Spermatogenesis: Process of sperm production



Sperm precursor cells called spermatogonia
Meiosis produces primary spermatocyte, which forms four
spermatids with 23 chromosomes
Spermatozoa: Highly specialized cells
•
•
•
Head contains genetic material
Acrosome contains enzymes to assist sperm in penetration
of ovum
Mitochondria in midpiece provide energy for movement
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Male Reproductive System (Cont.)

Testes

Testis functions
•
Production of testosterone by interstitial cells



Testosterone “masculinizes” and promotes development of
male accessory organs
Promotes and maintains development of male accessory
organs
Stimulates protein anabolism and development of muscle
strength
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11
Spermatogenesis
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Male Reproductive System (Cont.)

Reproductive ducts: Ducts through which
sperm pass after exiting testes until they exit
from the body

Epididymis: Single, coiled tube about 6 m in
length; lies along the top and behind the testis in
the scrotum
•
Sperm mature and develop the capacity for motility as
they pass through epididymis
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Male Reproductive System (Cont.)

Reproductive ducts

Vas deferens (ductus deferens)
•
•
•

Receives sperm from the epididymis and transports them
from scrotal sac through the abdominal cavity
Passes through inguinal canal
Joins duct of seminal vesicle to form the ejaculatory duct
Ejaculatory duct and urethra
•
Vas deferens joins the duct from the seminal vesicle to
form the ejaculatory duct
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Male Reproductive System (Cont.)

Accessory glands

Semen
•

Mixture of sperm and secretions of accessory sex
glands; averages 3 to 5 mL per ejaculation, with each
milliliter containing about 100 million sperm
Seminal vesicles
•
•
Pouchlike glands that produce about 60% of seminal
fluid volume
Secretion is yellowish, thick, and rich in fructose to
provide energy needed by sperm for motility
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Male Reproductive System (Cont.)

Accessory glands

Prostate gland
•
•
•
•

Shaped like a doughnut and located below bladder
Urethra passes through the gland
Secretion represents 30% of seminal fluid volume; thin
and milk-colored
Activates sperm and is needed for ongoing sperm motility
Bulbourethral (Cowper) glands
•
•
Resemble peas in size and shape
Secrete mucus-like fluid constituting less than 5% of
seminal fluid volume
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Male Reproductive System (Cont.)

External genitals


Penis and scrotum called genitalia
Penis has three columns of erectile tissue
•
•


Two dorsal columns called corpora cavernosa
One ventral column surrounding urethra called corpus
spongiosum
Glans penis covered by foreskin (prepuce)
Surgical removal of foreskin called circumcision
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Female Reproductive System

Structural plan: Organs classified as essential
or accessory


Essential organs: Gonads (ovaries), which
produce sex cells (ova)
Accessory organs
•
Ducts or modified ducts

•
Sex glands

•
Including oviducts, uterus, and vagina
Including the breasts
External genitals
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Organization of the
Female Reproductive System
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Female Reproductive System (Cont.)

Ovaries

Structure and location
•
•
•
•
Paired glands weighing about 3 g each
Resemble large almonds
Attached to ligaments in pelvic cavity on each side of uterus
Microscopic structure





Ovarian follicles contain an oocyte, which is an immature sex
cell (about 1 million at birth)
Primary follicles, about 400,000 at puberty, are covered with
granulosa cells
About 350 to 500 mature follicles (often called graafian follicles)
ovulate during the reproductive lifetime of most women
Secondary follicles have a hollow chamber called the antrum
Corpus luteum forms after ovulation
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Ovary
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Female Reproductive System (Cont.)

Ovaries

Ovary functions
•
Oogenesis

•
This meiotic cell division produces daughter cells with
equal chromosome numbers (23) but unequal cytoplasm;
ovum is large; polar bodies are small and degenerate
Production of estrogen and progesterone




Granulosa cells surrounding the oocyte in the mature and
growing follicles produce estrogen
Corpus luteum produces progesterone
Estrogen causes development and maintenance
of secondary sex characteristics
Progesterone stimulates secretory activity of uterine
epithelium and assists estrogen in initiating menses
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Female Reproductive System (Cont.)

Reproductive ducts

Uterine (fallopian) tubes (oviducts)
•
•
•

Extend about 10 cm from uterus into abdominal cavity
Expanded distal end surrounded by fimbriae
Mucosal lining of tube is directly continuous with lining of
abdominal cavity
Uterus
•
•
•
•
•
Composed of body, fundus, and cervix
Lies in pelvic cavity just behind urinary bladder
Myometrium is muscle layer
Endometrium lost in menstruation
Menopause: End of repetitive menstrual cycles (about 45
to 50 years of age)
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Female Reproductive System (Cont.)

Reproductive ducts

Vagina
•
•
•
Distensible tube about 10 cm long
Located between urinary bladder and rectum in the
pelvis
Receives penis during sexual intercourse and is birth
canal for normal delivery of baby at end of term of
pregnancy
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Uterus
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Female Reproductive System (Cont.)

Accessory glands

Vestibular glands
•
•

Secrete mucus lubricating fluid
Ducts open between labia minora
Breasts
•
•
•
•
Located over pectoral muscles of thorax
Size determined by fat quantity more than amount
of glandular (milk-secreting) tissue
Lactiferous ducts drain at nipple, which is surrounded by
pigmented areola
Lymphatic drainage important in spread of cancer cells to
other body areas
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Lateral View of the Breast
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Female Reproductive System (Cont.)

External genitals


Vulva: Several structures, which includes mons
pubis, clitoris, external urinary meatus, labia
minora, hymen, openings of vestibular gland
ducts, orifice (opening) of vagina, and labia majora
Perineum
•
•
Area between vaginal opening and anus
Surgical cut during childbirth called episiotomy
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External Genitals of the Female
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Female Reproductive System (Cont.)

Menstrual cycle: Involves many changes in
the uterus, ovaries, vagina, and breasts


Length: About 28 days, varies from month to
month among individuals and in the same
individual
Phases
•
Menses

About the first 4 or 5 days of the cycle, varies somewhat;
characterized by sloughing of bits of endometrium (uterine
lining) with bleeding
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Female Reproductive System (Cont.)

Menstrual cycle

Phases
•
Proliferative phase

•
Days between the end of menses and secretory phase;
varies in length; the shorter the cycle, the shorter the
proliferative phase; the longer the cycle, the longer the
proliferative phase
Secretory phase

Days between ovulation and beginning of next menses;
secretory about 14 days before next menses; characterized
by further thickening of endometrium and secretion by its
glands in preparation for implantation of fertilized ovum;
combined actions of the anterior pituitary hormones FSH and
LH cause ovulation; sudden sharp decrease in estrogens and
progesterone bring on menstruation if pregnancy does not
occur
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31
A 28-Day Menstrual Cycle
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32
Human Menstrual Cycle
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33
Female Reproductive System (Cont.)

Menstrual cycle

Ovulation: Typically occurs 14 days before the
next menses begins
•
•
•
Timing of ovulation has great practical importance
because of the possibility of fertilization
Most sperm retain their fertilizing power for only 24 to 72
hours after being deposited into female reproductive tract
A woman's fertile period lasts only a few days each
month
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34
Female Reproductive System (Cont.)

Menstrual cycle

Control of the menstrual cycle
•
•
•
Secretion of gonadotropin-releasing hormone (GnRH)
stimulates the secretion of FSH and LH from the anterior
pituitary gland
Ovulation occurs because of the combined actions of the
two anterior pituitary hormones
Birth control pills that contain estrogen substances
suppress FSH secretion
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Summary of the
Reproductive Systems



Reproductive systems in both sexes revolve
around the production of reproductive cells
(gametes)
Production of sex hormones is required for
development of secondary sex characteristics
and for normal reproductive functions in both
sexes
Both men and women have similar structures
to accomplish complementary functions
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36
Summary of the
Reproductive Systems (Cont.)
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37
Questions?
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38