A&P_CH25_REPRODUCTIVE_SYSTEM_FINAL sc.pptx PDF

25: Reproductive System Anatomy and Physiology in Context Chapter 25 Part 1 Objective 25 Reproductive Overview 25.1 Gametogenesis: The Big Picture 25.2 Reproductive Anatomy 25.3 Male Reproductive Tract 25.4 Male Accessory Glands 25.5 Male External Genitalia 25.6 Femal...

25: Reproductive System Anatomy and Physiology in Context Chapter 25 Part 1 Objective 25 Reproductive Overview 25.1 Gametogenesis: The Big Picture 25.2 Reproductive Anatomy 25.3 Male Reproductive Tract 25.4 Male Accessory Glands 25.5 Male External Genitalia 25.6 Female Reproductive Tract 25.7 Female External Genitalia 25.8 Hormonal Regulation of Reproduction 25.9 Puberty 25.10 Reproductive System and Aging 25.1 Gametogenesis: The Big Picture Chapter 25: Reproductive System Reproduction/Procreation A Fundamental Characteristic of Life Creation of a completely different person Sexual dimorphism Sex versus Gender 1. Sex: describes an individual biological characteristic can be described by your genotype or phenotype 2. Gender: differentiates masculinity and femininity Gametes 25.1.1 The Earliest Step of Gametogenesis GAMETOGENESIS: production of gametes Females: oogenesis; produces an ovum; takes 300 days to complete Males: spermatogenesis; produces a spermatozoa; takes 74 days to complete Gametogenesis begins around 5th week of embryonic development Primordial germ cells (PGCs) migrate to genital ridges PGCs mitotically divide during migration and differentiate into 25.1.2 The Basic, Shared Steps of Gametogenesis Increase the germline pool Diploid cells progressing through meiosis I Haploid cells progressing through meiosis II Mitosis versus Meiosis Prophase, Metaphase, Anaphase and Telophase 25.1.3 Spermatogenesis From Puberty Onward (1) Stem cell population Undergoing mitosis to maintain stem cell pool and generate Type B spermatogonia Undergo further mitosis to double the pool of germ cells entering the next step In Seminiferous Tubule near Sertoli Cells 25.1.4 Spermatogenesis From Puberty Onward (2) Type B Spermatogonia First meiotic division Second meiotic division Organelle and cytoplasm modification and rearrangement  25.1.5 Anatomy of the Spermatozoon Spermatozoa: the only self-propelled, swimming cells of the human body Golgi apparatusCentrioles Mitochondria Cytoplasm 25.1.6 The Spermatogenic Cycle Takes Approximately 74 Days At any given time, there are approx. 5 cohorts of generations concurrently advancing through development Hundreds of seminiferous tubules containing millions of spermatogonia Entire testis produces about  25.1.7 The Phases of Oogenesis Week 8 600,000 week 20 7,000,000 Begins during embryogenesis; continues at puberty Haploid nucleus with very little cytoplasm Secondary meiotic division occurs with male gamete present 25.2 Reproductive Anatomy Chapter 25: Reproductive System 25.2.1 Shared Anatomy of the Perineum 25.3 The Male Reproductive Tract Chapter 25: Reproductive System  25.3.1 The Male Reproductive Tract: The Testis ANATOMY FEATURES Normal human males have two testes These are paired ovoid gonads that are housed in the pouch-like scrotum Each testis is individually surrounded by the tunica vaginalis and tunica albuginea The tunica albuginea projects internally to divide the testis into  25.3.2 The Male Reproductive Tract: Seminiferous Tubules ANATOMY FEATURES Formed by interconnected Sertoli cells Functions of Sertoli cells:  Direct germ cell development  Scavenge cellular debris/damaged cells  Produce seminiferous fluid  FSH-responsive  Produce inhibin  Produce androgen-binding protein (ABP) 25.3.3 The Journey of Developing Germ Cells Through the Seminiferous Tubules Developing germ cells Tight junction assembly and re- travel towards lumen assembly  25.3.4 The Male Reproductive Tract: The Epididymis ANATOMY FEATURES Fluid and sperm cells travel through a series of tubules until converging into the epididymis Epididymis: Long, thin, convoluted single duct Lies against the testis, coiled down to 1/2000th of its actual size Divided into lobules; maintains tight junctions  25.3.5 The Male Reproductive Tract: The Ductus Deferens ANATOMY FEATURES Structural continuation of the epididymis Travels within the spermatic cord (with testicular arteries, veins and nerves) until the pelvic cavity Enlarges to form its ampulla before connecting with the seminal vesicle Image courtesy of Jpogi in the Public Has three tissue layers: outer  25.3.6 The Male Reproductive Tract: The Ejaculatory Duct and Male Urethra ANATOMY FEATURES Paired ejaculatory ducts: 1-2 cm each; connect ductus deferens to urethra; mixes sperm cells with seminal plasma Male urethra: divided into 3 layers  Prostatic urethra  Membranous urethra  Spongy urethra Collectively, 3 urethra layers conduct semen out of the male reproductive tract during ejaculation 25.4 The Male Accessory Sex Glands Chapter 25: Reproductive System  25.4.1 Male Accessory Sex Glands: Seminal Vesicles ANATOMY FEATURES Excretory duct on each gland joins with ampulla of ductus deferens to form ejaculatory duct Lumen consist of highly- convoluted irregular mucosa (increases surface area) Surrounded by 2 layers of smooth muscle (squeezes products out during Image courtesy of Nephron under CC BY-SA ejaculation)  25.4.2 Male Accessory Sex Glands: The Prostate Gland ANATOMY FEATURES Largest human accessory sex gland Consists of many lobules that all open up into prostatic urethra Produces ~30% of seminal plasma by volume Secretes factors that promote sperm survival, activation and fertilization (citric acid, PSAP, zinc, prostate-specific antigen,  25.4.3 Male Accessory Sex Glands: The Bulbourethral Gland ANATOMY FEATURES 2 cm-long ducts join with spongy urethra Secretions make up first fraction of ejaculate (~5% of total) Typically does not mix with sperm cells; sometimes called pre-ejaculate Clear, alkaline fluid consists of lubricating proteins and neutralizing mucins 25.5 The Male External Genitalia Chapter 25: Reproductive System  25.5.1 Male External Genitalia: The Penis ANATOMY FEATURES Elongated structure that grows in both girth and length during sexual arousal Divided structurally into three parts: 1. Roots (attach penis to pelvic girdle) 2. Body (contains penile urethra and corpora cavernosa) 25.5.2 Engorgement of the Penis During Sexual Arousal Paired corpora cavernosa: erectile bodies located dorsolaterally to the single corpora spongiosum Blood enters corpora cavernosa through cavernosal artery Primary function of the corpora spongiosum: ensures the urethra remains a functional ejaculatory pathway during erection  25.5.3 Male External Genitalia: The Scrotum ANATOMY FEATURES Primary function: maintains temperature of testes at 34°C to promote spermatogenesis Suspended at base of pelvis; houses testes, epididymis and proximal portion of ductus deferens Bisected at midline to create 2 compartments Temperature monitored with thermoreceptors 25.6 Female Reproductive System Chapter 25: Reproductive System 25 Reproductive Overview 25.1 Gametogenesis: The Big Picture 25.2 Reproductive Anatomy 25.3 Male Reproductive Tract 25.4 Male Accessory Glands 25.5 Male External Genitalia 25.6 Female Reproductive Tract 25.7 Female External Genitalia 25.8 Hormonal Regulation of Reproduction 25.9 Puberty 25.10 Reproductive System and  25.6.1 The Female Reproductive System: Ovaries ANATOMY FEATURES Positioned on either side of the uterus, anchored by the mesovarium Ovarian arteries, veins and nerves pass out of the ovary at the hilum Outer cortex of ovary: dense connective tissue interspersed with thousands of ovarian follicles containing developing germ cells Inner medulla: areolar connective  25.6.2 The Female Reproductive System: Folliculogenesis Theca cells: steroidogenic cells; convert cholesterol into androgens Granulosa cells: responsible for maintenance and maturation of oocytes; convert androgens into estrogen Generated through further expansion of Germ granulosa cell cells, reserves development of the of antrum; ovary theca expands into Recruited follicle; develops 2 layers Develop through mitotic zona pellucida (protective expansion of granulosa layer) cells  25.6.3 The Female Reproductive System: The Ovarian Follicle ANATOMY FEATURES As the tertiary follicle develops, the oocyte and surrounding granulosa cells get displaced to one side of the antrum Specialized granulosa cells develop (cumulus oosphorus)  later develop into corona radiata Other granulosa and thecal cells will develop into luteal cells Typically, only 1 tertiary follicle  25.6.4 The Female Reproductive System: The Corpus Luteum ANATOMY FEATURES Corpus luteum: transient endocrine organ formed from granulosa and thecal cells Persists and secretes hormones if pregnancy occurs If pregnancy does not happen, luteal cells degenerate and are replaced by the corpus albicans The corpus albicans is resorbed after a Image courtesy of Ed Uthman under CC BY- few months Uterus, Ovaries and Follicles cilia etopic  25.6.5 The Female Reproductive System: The Uterine Ducts ANATOMY FEATURES Extend laterally from uterus; divided into four distinct regions: 1. Infundibulum: has fimbriae that sweep oocytes into ostium 2. Ampulla: site of fertilization 3. Isthmus: accounts for 1/3 of length  25.6.6 The Female Reproductive System: Layers Of The Uterine also called fallopian Ducts tubes ANATOMY FEATURES Outermost layer: thin, protective serosa Middle layer: two smooth muscle layers; contractions serve to transport the oocyte/blastocyst to the uterus Inner layer: highly-folded mucosa lined with ciliated epithelium  Epithelial cells produce tubular fluid that promotes  25.6.7 The Female Reproductive System: The Uterus ANATOMY FEATURES Structurally divided into 4 regions: 1. Fundus (base of inverted pear shape) 2. Body (broad region) 3. Isthmus (narrow region) 4. Cervix (projects into vagina) Function: structure of gestation (receives, retains and nourishes fetus)  25.6.8 The Female Reproductive System: The Layers of the Uterus ANATOMY FEATURES Perimetrium: outer serosa Myometrium: 3 layers of smooth muscle Endometrium: site of implantation  Basal layer: permanent structure; contains arteries and acini from uterine glands  Functional layer: hormone- responsive layer; grows in 25.6.9 The Female Reproductive System: Cervix and Vagina CERVIX VAGINA Dome-like structure of uterus Functions: copulatory organ, that projects into vagina passageway for outflow of menstruation, and birth canal The endometrium is not shed during parturition during menses, and myometrium is much thinner Consists of three layers: outer (functional layer) adventitia, middle muscularis and inner mucosa Cervical canal joins uterus to vagina Natural home to several non- pathogenic microorganisms, Mucosa produce secretions due to warm and moist that create a mucous plug, environment 25.7 The Female External Genitalia Chapter 25: Reproductive System  25.7.1 Female External Genitalia: The Vulva ANATOMY FEATURES Mons pubis: Rounded cushion of fatty tissue covered by skin and pubic hair Labia majora: Connective tissue, adipose tissue and thickened skin Pudendal cleft: A furrow separating the paired labia majora Labia minora: Normally cover vaginal orifice, but swell and separate when sexually aroused  25.7.2 Female External Genitalia: The Vestibule ANATOMY FEATURES The vestibule lies between and is hidden by the paired labia minora Largely occupied by vaginal orifice Hymen (connective tissue membrane) covers vaginal orifice in pre-coital females Ducts of paraurethral and greater vestibular glands also  25.7.3 Female External Genitalia: The Clitoris ANATOMY FEATURES Erectile body; partly homologous to the male penis Consists of a cylindrical shaft containing corpora cavernosa and a distal glans Rich in pressure and temperature receptors The vestibular bulbs are found on either side of the vaginal orifice, and also engorge during sexual 25.8 Hormonal Regulation of Reproduction Chapter 25: Reproductive System 25.8.1 Gametogenesis Is Regulated in Both Sexes by the Hypothalamic- Pituitary-Gonadal Axis GnRH synthesized by hypothalamic neurons Released through hypothalamic- hypophyseal portal system Stimulates release of gonadotropins LH and FSH from anterior pituitary Gonadotropins enter general circulation Stimulate gametogenesis and steroidogenesis in the gonads Steroid Hormones Cholesterol Progesterone * Dihydro- Testosterone testosterone (DHT) aromatase both sexes develop external male genitalia Corticosterone Estradiol KEY 5-reductase Aldosterone * Intermediate steps 25.8.2 Male Reproductive Endocrinology Female Menstrual Cycle Ovarian Cycle Uterine Cycle 25.8.3 The Menstrual Cycle (1): The Ovarian Cycle Follicular phase Luteal phase Rapid growth of Presence of corpus tertiary follicle in luteum; preparation for progesterone  25.8.4 The Menstrual Cycle (2): The Uterine Cycle Dominant follicle rapidly Endometrium Characteriz growing; estrogen-priming becomes ed by for endometrial repair, vascularized in menses regeneration preparation for pregnancy 25.8.5 Hormones During the Menstrual Cycle (1): The Early Follicular Phase Estrogen at its lowest FSH levels rise at first, stimulating follicle growth FSH then downregulated by inhibin 25.8.6 Hormones During the Menstrual Cycle (2): The Mid-Follicular Phase One follicle remains due to low FSH Estrogen levels rapidly rise Small surge in LH promotes even more estrogen 25.8.7 Hormones During the Menstrual Cycle (3): The Late Follicular Phase and LH Surge Estrogen levels reach their peak Switches from negative to positive feedback  LH surge Rapid loss of estrogen 25.8.8 Hormones During the Menstrual Cycle (4): Progesterone and the Corpus Luteum Progesterone prepares endometrium, uterus for pregnancy LH levels decline and estrogen levels rise In absence of pregnancy, corpus Female Menstrual Cycle Phases of the Follicular Phase Ovulation Luteal Phase Ovarian Cycle LH Gonadotrophic hormone levels FSH Ovarian cycle Corpus Mature Primary Corpus follicle Theca Antrum Ovulation luteum corpus albicans formation luteum Progesterone Ovarian hormone Estrogen Inhibin levels Uterine cycle Phases of the PROLIFERATIVE Uterine Cycle MENSES SECRETORY PHASE PHASE 36.7 Basal body temperature (–C) 36.4 DAYS 28/0 7 14 21 28/0 25.9 Common Origins Chapter 25: Reproductive System  25.9.1 Organization of the Primordial Gonad 8 week-old embryo: Has potential to form parts of male reproductive tract Has potential to form parts of female reproductive tract potential to Path of primordial develop into germ cells ovary testis 25.9.2 Sexual Dimorphism in Early Development SRY no SRY XY XX 25.10 Puberty Chapter 25: Reproductive System 25.10.1 Puberty Is the Event That Leads to Sexual Maturity Steps of puberty: 1. Adrenarche Increased production of androgens in adrenal cortex Age 6-8 2. Gonadarche Structural and functional maturation of gonads so they can produce gametes and steroids Males: primarily testosterone Females: estrogen, progesterone, growth hormone, insulin, thyroid 25.11 Reproductive Systems and Aging Chapter 25: Reproductive System 25.11.1 Termination of Reproductive Years: The Climacteric FEATURES OF MALE FEATURES OF FEMALE Decreased testosterone CLIMACTERIC Drop in circulating estrogen CLIMACTERIC production, leading to loss in testicular volume and sperm Ovaries are devoid of follicles production and menstruation stops Other symptoms of reduced Reproductive organs undergo circulating testosterone levels: modest atrophy; vagina lubrication is reduced  Diminished sex drive  Occasional mood swings Breast tissue atrophies  Erectile dysfunction/impotence Hot flashes; figure becomes more androgynous; bones