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Biology 221 Anatomy & Physiology II. TOPIC 12 Reproductive System. Chapter 28 pp. 1071-1107. E. Lathrop-Davis / E. Gorski / S. Kabrhel. Male Anatomy Overview. Consists of: Testes Ducts epididymus ductus (vas) deferens ejaculatory duct urethra Penis Accessory glands

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TOPIC 12 Reproductive System

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Biology 221

Anatomy & Physiology II

TOPIC 12 Reproductive System

Chapter 28

pp. 1071-1107

E. Lathrop-Davis / E. Gorski / S. Kabrhel


Male Anatomy Overview

Consists of:

  • Testes

  • Ducts

    • epididymus

    • ductus (vas) deferens

    • ejaculatory duct

    • urethra

  • Penis

  • Accessory glands

    • seminal vesicles

    • prostate

    • bulblurethral (Cowper’s)

http://www.msms.doe.k12.ms.us/biology/anatomy/reproductive/376a.gif

Fig. 28.1, p. 1071


Male: Testis

  • Located in scrotum

    • temperature regulation (keeps them at about 33oC)

  • Structure of testis

    • seminiferous tubules

    • interstitial cells (cells of Leydig)

    • rete testis

Fig. 28.3, p. 1073


Male: Testis – Seminiferous Tubules

  • Produce sperm

  • Sustentacular (Sertoli) cells (5) – support spermatocytes and spermatozoa, and produce inhibin (inhibits FSH/LH secretion)

http://www.usc.edu/hsc/dental/ghisto/rep/d_74.html

http://www.usc.edu/hsc/dental/ghisto/rep/d_74.html


Male: Testis – Interstitial Cells and Rete Testis

  • Interstitial cells (between seminiferous tubules) – produce testosterone (promotes sperm formation)

  • Rete testis

    • first collection area

    • network of tubules on posterior side

    • Lead to epididymus

http://www.usc.edu/hsc/dental/ghisto/rep/d_74.html

http://www.usc.edu/hsc/dental/ghisto/rep/d_75.html

Fig. 28.3, p. 1073


Male: Testis Coverings

  • tunica vaginalis (TV) – connective tissue, derived from peritoneum

  • tunica albuginea (TA) – fibrous capsule

  • septa (S; singular = septum) – extensions of tunica albuginea; divide testis into sections

Fig. 28.3, p. 1073

http://www.usc.edu/hsc/dental/ghisto/rep/d_72.html


Male: Duct System

  • Epididymis – site of sperm maturation

  • Ductus (vas) deferens – carries sperm away from testis to ejaculatory duct

  • Ejaculatory Duct – extends from where ducts from seminal vesicles join ductus deferens to urethra

Fig. 28.1, p. 1071

http://www.msms.doe.k12.ms.us/biology/anatomy/reproductive/376a.gif


Male: Urethra

  • Prostatic urethra – runs through prostate gland

  • Membranous urethra – runs from prostate to penis

  • Penile urethra – runs through penis

Fig. 28.4, p. 1075

http://www.nku.edu/~dempseyd/REPRODUCTION_2.htm


Male: Penis

  • Designed to deliver sperm into vagina of female

  • Erectile tissues

    • Corpora cavernosa (CC)

    • Corpus spongiosum (CS) – surrounds urethra

Fig. 28.4, p. 1075

http://wbiomed.curtin.edu.ou/teach/humanbiol/hb134/134hist/penis.htm


Male Accessory Glands & Semen

  • Semen = sperm plus products of the accessory glands that support and nourish the sperm + sperm

  • Glands (overview)

    • Seminal vesicles (SV)

    • Prostate gland

    • Bulbourethral (Cowper’s) glands

Fig. 28.1, p. 1071


Male Accessory Glands: Seminal Vesicles

  • produce about 60% of all semen

  • alkaline fluid – neutralizes acidity of vagina

  • fructose – nourishes sperm

Fig. 28.1, p. 1071


Male Accessory Glands: Prostate

  • encircles urethra below bladder

  • produces about 30% of semen

  • products play a role in activating and protecting sperm

  • citrate nourishes sperm

http://www.usc.edu/hsc/dental/ghisto/rep/d_96.html

Fig. 28.1, p. 1071


Male Accessory Gland:Bulbourethral Glands

  • Lie near base of penis

  • Produce mucus that neutralizes acidity of traces of urine in urethra

Fig. 28.1, p. 1071


Male Reproductive Physiology: Sperm Production Overview

  • Sperm (and ova) are produce by meiotic cell division

  • Sperm production involves two stages:

    • Spermatogenesis – in which diploid cells divide by meiotic cell division to yield haploid gametes

    • Spermiogenesis – maturation of spermatids into functional spermatozoa (sperm)


Single division

2 divisions

  • Meiosis I – reduces number of chromosomes by half

  • Meiosis II – separates chromatids into 4 separate haploid cells

Produces 2 genetically identical diploid daughter cells

Produces 4 genetically distinct haploid daughter cells

Comparison of Mitosis & Meiosis

Mitosis

Meiosis

Fig. 28.6, p. 1078


Male: Spermiogenesis

Development of:

  • Flagellum for movement

  • Acrosome (contains digestive enzymes for egg penetration)

  • Midpiece (mitochondria -energy for movement)

Fig. 28.9, p. 1082


Male: Sustentacular Cells

  • Also called Sertoli cells

  • Surround and support developing spermatocytes and spermatids

  • Extend from basal lamina to lumen of tubule

Fig. 28.8, p. 1081


Male: Sustentacular Cells

  • Form blood-testis barrier

    • cells joined by tight junctions - prevents contact between developing sperm and blood

    • produce fluid different from surrounding interstitial fluid (higher in androgens, amino acids, potassium)

    • important because sperm are first produced after immune system has developed sense of “self”

      • sperm would be recognized as foreign if contacted blood


Male: Hormonal Regulation of Function

Hypothalamus secretes GnRH

(Gonadotropin-releasing hormone)

Stimulates anterior pituitary to release

FSH LH



  • indirectly stimulates stimulates testosterone secretion testosterone

  • stimulates spermatogenesissecretion

  • stimulates inhibin secretion

    (inhibits FSH and LH production)

Fig. 28.10, p. 1085

http://www.uronet.org/visual/nov99/3.htm


Male: Testosterone

Stimulates

  • spermatogenesis

  • development and maintenance of male secondary sex characteristics (e.g., facial hair, large muscles, etc.) and male reproductive organs

  • development of sexual drive in CNS

  • protein synthesis in muscle cells and growth of muscle and bone

Fig. 28.10, p. 1085

http://www.uronet.org/visual/nov99/1.htm


Female Anatomy Overview

Consists of:

  • Ovaries

  • Fallopian (uterine) tubes (oviducts)

  • Uterus

  • Vagina

  • Mammary glands

  • Supporting structures

http://www.med.umich.edu/lrc/coursepages/M1/anatomy/html/radiology/pelvis/hysterosalpingogram.html

Fig. 28.11, p. 1086


Female: Ovaries

  • Located lateral to uterus

  • Ligaments anchor ovary to other structures

    • ovarian ligament – anchors ovary to uterus

    • broad ligament – parietal peritoneal tissue

      • suspensory ligament – anchors ovary to lateral pelvic wall

      • mesovarium – holds ovary between ovarian and suspensory ligaments

  • Contains oocytes surrounded by follicles

  • Release secondary oocytes into pelvic cavity

Fig. 28.14, p. 1089


Female: Uterine (Fallopian) Tubes

  • Carry oocyte toward uterus

  • Fimbriae (F) immediately pick up secondary oocyte released from ovary and transfer it into UT

  • Smooth muscle and cilia of simple columnar epithelium help move oocyte toward uterus

Fig. 28.14, p. 1089

http://www.med.umich.edu/lrc/coursepages/M1/anatomy/html/radiology/pelvis/hysterosalpingogram.html


Female: Uterus

  • Normal site of implantation of fertilized ovum and development of fetus

  • Layers

    • endometrium (inner layer)

    • myometrium (smooth muscle)

    • perimetrium (covering of visceral peritoneum)

Fig. 28.14, p. 1089


Female: Uterus – Endometrium

  • Consists of two sublayers

    • stratum functionalis (f) – undergoes cyclical changes every month

    • stratum basalis (b) – overlies myometrium (m) and forms a new stratum functionalis

  • Forms maternal part of placenta

http://www.usc.edu/hsc/dental/ghisto/rep/d_33.html

http://www.usc.edu/hsc/dental/ghisto/rep/d_34.html


Female: Myometrium & Perimetrium

  • Myometrium

    • consists of smooth muscle

    • contracts to expel sloughed off endometrial tissue or fetus

  • Perimetrium(serosa)

    • peritoneal covering

Fig. 28.14, p. 1089


Female: Cervix and Vagina

  • Cervix – narrow “neck” of uterus

  • Vagina

    • “birth canal”

    • lined with stratified squamous epithelium

Fig. 28.14, p. 1089


Mammary Glands

  • Modified sweat glands

  • Only functional in females

  • Produce milk to nourish newborn

  • Hormonal control

    • prolactin - stimulates milk production in lactating female

    • oxytocin - stimulates milk ejection

Fig. 28.17, p. 1093


Female: Ovarian Cycle Overview

  • Consists of two phases: Follicular (1-6 in diagram) & Luteal (7-9 in diagram)

Fig. 28.20, p. 1097


Follicular Phase – 1st to 14th Day

  • Several primordial follicles develop into primary follicles

  • Primary follicle develops into secondary follicle

    • zona pellucida (thick, transparent membrane around oocyte)

    • begins to produce estrogens

    • antrum (opening around oocyte) forms

  • Secondary follicle (when antrum is present) becomes Vesicular follicle (Graafian follicle)

    • corona radiata forms (cells surrounding oocyte)

    • primary oocyte divides (finishes meiosis I) to form 1 secondary oocyte and 1 polar body

Fig. 28.12, p. 1087

Fig. 28.19, p. 1095


Ovulation and Luteal Phase – 14th to 28th day

  • Ovulation = release of secondary oocyte (arrested in metaphase of meiosis II) from ovary

  • Luteal Phase – 14th to 28th day

    • cells of ruptured Graafian follicle become corpus luteum which begins to secrete progesterone and continue to secrete estrogen

    • corpus luteum degenerates in about 10 days if pregnancy does not occur then becomes corpus albicans

Fig. 28.12, p. 1087


Ovarian Cycle: Hormonal Control

  • Hypothalamus secretes GnRH (gonadotropin releasing hormone)

  • GnRH stimulates release of FSH (follicle stimulating hormone) and LH (lutenizing hormone) from anterior pituitary

    • FSH (& LH) stimulate follicle growth

Fig. 28.21, p. 1098


Ovarian Cycle: Hormonal Control

  • Enlarged follicles begin to secrete estrogens

  • Rising estrogen levels initially inhibitrelease of FSH & LH from anterior pituitary, but also stimulate it to produce and accumulate these hormones (i.e., accumulate FSH and LH)

Fig. 28.21, p. 1098


Ovarian Cycle: Hormonal Control

  • Once estrogen levels reach critical level, exert positive feedback on hypothalamus & pituitary

    • result is sudden surge of LH

  • Surge of LH results in:

    • completion of meiosis I

    • release of secondary oocyte from Graafian follicle (i.e., ovulation)

  • Ovulation results from positive feedback influence of estrogen on secretion of LH

Fig. 28.21, p. 1098


Ovarian Cycle: Hormonal Control

  • Surge of LH causes ruptured follicle to become corpus luteum and stimulates production of estrogens and progestins from it

  • Increased progesterone and estrogen cause decline in LH; corpus luteum is less stimulated and eventually becomes corpus albicans

Fig. 28.21, p. 1098


Uterine (Menstrual) Cycle

  • Cyclical changes in the endometrium that prepare it for implantation of a fertilized ovum.

  • Three phases: menstrual, proliferative, secretory

Fig. 28.15, p. 1091

Fig. 28.22, p. 1100


Menstrual Phase (Days 1-5)

  • Stratum functionalis is shed (passes through vagina as menstrual flow)

  • This is a response to declining estrogen levels

http://lpc1.clpccd.cc.ca.us/lpc/zingg/anat/alecture/ach27f/sld021.htm


Proliferative Phase (Days 6-14)

  • Stratum functionalis rebuilt by stratum basale in response to stimulation from ovarian estrogens

  • Endometrial glands become larger

  • Estrogen induces formation of additional progesterone receptors

  • Increased blood supply


Secretory Phase (Days 15-28)

  • Endometrium continues to develop in response to ovarian progesterone

  • Secretion of nutrient substances begins

  • Toward end, decline in progesterone results in declining condition of blood vessels in stratum functionalis, eventually resulting in its loss (start of next menstrual phase)


Correlation of Hormones With Cycles

  • During menstrual phase, all hormones are at their lowest levels

  • During proliferative phase, estrogens secreted by ovary cause proliferation of endrometrial cells such that stratum functionalis is rebuilt from stratum basale

  • During secretory phase,

    • high levels of progesterone continue to stimulate development of stratum functionalis

    • Levels of estrogen decrease somewhat

Fig. 28.22


Disorders of Reproduction: STDs

  • Gonorrhea – infection by Neisseria gonnorrhoeae bacteria; causes inflammation of the urethra and can lead to pelvic inflammatory disease in females

  • Syphilis – infection by Treponema pallidum bacteria

  • Chlamydia – infection by Chlamydia bacteria; causes pelvic inflammatory disease, urethritis, among other things

  • Genital warts – infection by human papillomavirus (HPV); causes warts in genital area; increases probability of developing cervical or penile cancer

  • Genital herpes – infection by herpes simplex virus; causes lesions on genital area; treated with acyclovir


Other Disorders of Reproduction

  • Pelvic inflammatory disease (PID) - severe inflammation of lower peritoneal cavity generally caused by STDs

  • Ectopic pregnancy – implantation of embryo outside uterus (e.g., in oviduct or pelvic cavity)

  • Hypertrophy of prostate – enlargement of the prostate;impinges on prostate urethra making urination difficult and increasing the likelihood of bladder infection; common in elderly males

  • Breast cancer - cancer of the mammary gland; strikes 1:8 women


Important Developmental Milestones

  • 8 weeks

    • ossification begins

    • blood cells begin to be formed by liver

    • all systems present (at least as basic plan)

  • 9-12 weeks

    • bone marrow begins to form blood cells

  • 26 weeks

    • surfactant production begins in lung

  • 38-42 weeks

    • birth

      • if less than 38 weeks, systems not as developed

      • if more than 42 weeks, placenta starts to degrade


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