The Reproductive System and
Development
Chapter 25 – Lecture Notes
to accompany
Anatomy and Physiology: From Science to Life
textbook by
Gail Jenkins, Christopher Kemnitz, Gerard Tortora
Chapter Overview
25.1 Sperm Production
25.2 Male Reproductive System
25.3 Female Reproductive System
25.4 Vagina and Mammary Glands
25.5 Ovarian and Uterine Cycle
25.6 Implantation of Blastocyst
25.7 Embryonic to Fetal Period
Chapter Overview
25.8 Maternal Changes During Pregnancy
25.9 Labor
25.10 Milk Production and Ejection
Essential Terms
gamete
 germ cells with haploid number of chromosomes
fertilization
 occurs when sperm unites with secondary oocyte
pregnancy
 sequence of events resulting in birth of child
gonads
 male testes and female ovaries which secrete
hormones and produce gametes
Introduction
Sexual Reproduction
1.
2.
3.
4.
Males and females differ anatomically to
produce gametes and support a fetus
Fertilization is the result of male and
female gametes joining
Pregnancy begins with fertilization and
usually results in birth of a child
Gonads produce gametes and hormones
Concept 25.1
Sperm Production
Male Reproductive System
Testes – System of Ducts
1.
•
Epididymis, ductus deferens, ejaculatory ducts,
and urethra
Accessory glands
2.
•
Seminal vesicles, prostate, and bulbourethral
glands
Supporting Structures
3.
•
Scrotum and penis
Figure 25.1a
Figure 25.1b
Scrotum



Scrotal location and muscle contraction
regulate temperature of testes
Normal sperm production occurs 2-3°C lower
than core body temperature
Response to cool temperatures



Cremaster muscles contract to pull testes close to
body
Dartos muscles contract to tighten scrotum
Response to warm temperatures

Reverse of above actions
Figure 25.2
Testes



One testes in each sac of scrotum
Descend during seventh month of fetal
development
Tunica albuginea is located deep to tunica
vaginalis and forms 200-300 lobules


Lobules contain seminiferous tubules
Spermatogenesis carried out by seminiferous
tubules of testes
Figure 25.3a
Figure 25.3b
Figure 25.3c
Testes

Spermatogenic cells


Sertoli or sustentacular cells







Begin sperm production at puberty
Junctions form blood-testis barrier
Nourish spermatogenic cells
Carry out phagocytosis
Control spermatogenic movement
Produce fluid for transport
Secrete hormone inhibin
Leydig (interstitial) cells

Secrete testosterone
Figure 25.4a
Figure 25.4b
Spermatogenesis



Begins with spermatogonia and diploid
number of chromosomes
Some pass through blood-testis barrier
Primary spermatocytes also diploid
Figure 25.5
Spermatogenesis

Meiosis I




Crossing-over during metaphase I
Secondary spermatocytes result
Each with haploid number
Meiosis II


Results in four spermatids
Each with haploid number
Spermatogenesis


Cytoplasmic bridges link the four daughter
cells
Spermiogenesis




Transformation of spherical spermatids into
elongated sperm
Formation of arcosome
Flagellum develop
Mitochondria multiply
Sperm




300 million per day produced
Survive 48 hours in female reproductive tract
Sperm Parts
Head



Nucleus
Arcosome
Tail




Neck
Middle piece
Principal piece
End piece
Figure 25.6
Hormonal Control of Testes


Negative feedback loops control testosterone
release and spermatogenesis
Gonadotropin-releasing Hormone (GnRH)



Luteinizing hormone (LH)


Increased production at puberty
Stimulates secretion of LH and FSH
Stimulates Leydig cells
Follicle-stimulating hormone (FSH)

Stimulates Sertoli cells to secrete ABP
Figure 25.7
Hormonal Control of Testes

Testosterone





Dihydrotestosterone (DHT)


Stimulates development of external genitals
Androgen-binding Protein (ABP)


Principal androgen
Synthesized from cholesterol
Suppresses LH and GnRH secretion
Converted to DHT in prostate and seminal vesicles
Binds to and keeps testosterone levels high
Inhibin

Inhibits FSH secretion
Effects of Testosterone and
Dihydrotestosterone




Prenatal development
Development of male sexual characteristics
Development of sexual function
Stimulation of anabolism
Figure 25.8
Concept 25.2
Male Reproductive System
Reproductive System Ducts in Males

Ducts of testis






Seminiferous tubules
Straight tubules
Rete testis
Efferent ducts
Ductus epididymis
Epididymis





Site of sperm maturation and storage
Consists of ductus epididymis
Head – superior portion formed by efferent ducts of testis
Body
Tail – continues as ductus (vas) deferens
Ductus Deferens



Terminal portion is the ampulla
Conveys sperm from epididymis toward
urethra
Storage and reabsorption of sperm
Figure 25.9
Spermatic Cord


Supporting structure ascends out of scrotum
Comprised of several structures






Ductus deferens
Testicular artery
Pampiniform plexus
Autonomic nerves
Lymphatic vessels
Cremaster muscles
Ejaculatory Ducts


Formed by duct of seminal vesicle and
ampulla of ductus deferens
Eject sperm and seminal vesicle secretions
from urethra to exterior
Urethra


Shared by reproductive and urinary systems
3 subdivisions



Prostatic urethra
Membranous urethra
Spongy (penile) urethra
Accessory Sex Glands




Produce fluids to protect semen and facilitate
their movement
Seminal vesicles
Prostate
Bulbourethral or Cowper’s glands
Seminal Vesicles





Alkaline fluid
Fructose
Prostaglandins
Clotting proteins
Approximately 60% of semen volume
Prostate Gland








Citric acid
Proteolytic enzymes – prostate-specific
antigen (PSA)
Pepsinogen
Lysozyme
Amylase
Hyaluronidse
Milky, acidic fluid (pH ~ 6.5)
Approximately 25% semen volume
Bulbourethral / Cowper’s Glands



Pea sized glands active during sexual
arousal
Alkaline fluid
Secrete lubricating mucus
Semen





Combination of sperm and seminal fluid
2.5 – 5 mL per ejaculation
50 – 150 million sperm/ml
Alkaline pH ~ 7.2 – 7.7
Seminalplasmin – antibiotic
Penis



Contains urethra
Passage for sperm and urine
3 Parts





Root
Body
Glans penis
Erection maintained by parasympathetic
fibers
Ejaculation, a sympathetic reflex, releases
semen to exterior
Figure 25.10a
Figure 25.10b
Concept 25.3
Female Reproductive
System
Figure 25.11a
Figure 25.11b
Figure 25.12
Figure 25.13
Figure 25.14a
Figure 25.14b
Figure 25.15
Concept 25.4
Vagina and Mammary
Glands
Concept 25.5
Ovarian and Uterine
Cycle
Concept 25.6
Implantation of
Blastocyst in
Endometrium
Concept 25.7
Embryonic to Fetal
Period
Concept 25.8
Maternal Changes During
Pregnancy
Concept 25.9
Labor
Concept 25.10
Milk Production and
Ejection