The Reproductive System and DevelopmentChapter 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
IntroductionSexual Reproduction
1. Males and females differ anatomically to produce gametes and support a fetus
2. Fertilization is the result of male and female gametes joining
3. Pregnancy begins with fertilization and usually results in birth of a child
4. Gonads produce gametes and hormones
Concept 25.1
Sperm Production
Male Reproductive System
1. Testes – System of Ducts• Epididymis, ductus deferens, ejaculatory ducts,
and urethra
2. Accessory glands• Seminal vesicles, prostate, and bulbourethral
glands
3. Supporting Structures• 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 Begin sperm production at puberty
Sertoli or sustentacular cells 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) Increased production at puberty Stimulates secretion of LH and FSH
Luteinizing hormone (LH) Stimulates Leydig cells
Follicle-stimulating hormone (FSH) Stimulates Sertoli cells to secrete ABP
Figure 25.7
Hormonal Control of Testes Testosterone
Principal androgen Synthesized from cholesterol Suppresses LH and GnRH secretion Converted to DHT in prostate and seminal vesicles
Dihydrotestosterone (DHT) Stimulates development of external genitals
Androgen-binding Protein (ABP) 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