Male Reproductive Bio 202 Arizona State U Fall2023 PDF

ARIZONA STATE UNIVERSITY Male Reproductive College of Integrative Sciences & Arts Bio 202 A natomy & Physiology II Tonya A. Penkrot, Ph.D.  Reproductive System Primary sex organs (gonads): testes...

ARIZONA STATE UNIVERSITY Male Reproductive College of Integrative Sciences & Arts Bio 202 A natomy & Physiology II Tonya A. Penkrot, Ph.D.  Reproductive System Primary sex organs (gonads): testes and ovaries – Produce gametes (sex cells): sperm and ova – Secrete steroid sex hormones Androgens (males) testosterone Estrogens and progesterone (females) Accessory reproductive organs: ducts, glands, and external genitalia – Secondary sex organs: generally, the ducts & organs that bring the male and female gametes together Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Part 1 –Anatomy of Male Reproductive System Testes (within scrotum) produce sperm Sperm delivered to exterior through system of ducts – Epididymis ductus deferens ejaculatory duct urethra Testes: sperm-producing male gonads that lie within the scrotum Sperm is delivered to body through system of ducts: epididymis, ductus deferens, ejaculatory duct, and urethra Accessory sex glands: seminal glands, prostate, and bulbo-urethral glands Bio 202 ASU DPC T. Penkrot add to semen © 2016 Pearson Education, Inc. Figure 27.1 Reproductive organs of the male, sagittal view. Peritoneum Ureter Seminal gland (vesicle) Urinary bladder Ampulla of Prostatic urethra ductus deferens Pubis Ejaculatory duct Intermediate part of the urethra Rectum Urogenital diaphragm Prostate Corpus cavernosum Bulbo-urethral gland Corpus spongiosum Anus Spongy urethra Bulb of penis Glans penis Ductus (vas) deferens Epididymis Prepuce (foreskin) External urethral Scrotum orifice Testis Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  27.1 Scrotum and Testes The Scrotum Sac of skin and superficial fascia – Hangs outside abdominopelvic cavity – Contains paired testes 3°C lower than core body temperature Lower temperature is necessary for sperm production – Midline septum divides scrotum into two compartments, one for each testis Temperature is kept constant by two sets of muscles – Dartos muscle: smooth muscle; wrinkles scrotal skin; pulls scrotum close to body – Cremaster muscles: bands of skeletal muscle that © elevate Bio 202 ASU DPC T. Penkrot testes 2016 Pearson Education, Inc.  The Testes fluid can collect Each testis is surrounded by two tunics – Tunica vaginalis: outer layer derived from peritoneum – Tunica albuginea: inner layer forms fibrous capsule 88 s to Septa divide testis into ~250 lobules, each containing one to four seminiferous tubules – Site of sperm production Seminiferous tubules have thick, stratified epithelium surrounding central fluid-containing lumen – Epithelium contains spheroid spermatogenic cells (sperm- forming cells) embedded in support cells called sustentocytes Myoid cells surround each seminiferous tubule – Smooth muscle–like cells that may squeeze sperm and testicular fluids out of testes Tubules of each lobule converge to form the straight tubule Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.2 Relationships of the testis to the scrotum and spermatic cord. current Urinary bladder exchanger Superficial inguinal ring (end of inguinal canal) Testicular artery Spermatic cord Ductus (vas) deferens Penis Autonomic nerve fibers Pampiniform Septum of scrotum venous plexus Epididymis Cremaster muscle Tunica vaginalis External spermatic (from peritoneum) fascia Tunica albuginea Superficial fascia of testis Scrotum containing dartos muscle Internal spermatic Skin fascia Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  The Testes (cont.) Sperm is conveyed from seminiferous tubules to straight tubule rete testis efferent ductules epididymis – Epididymis is made up of the head, the body, and the tail – Sperm are stored in the tail until ejaculation Interstitial endocrine cells: located in soft tissue surrounding seminiferous tubules – Produce androgens, such as testosterone – Secrete it into interstitial fluid Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.3a Structure of the testis. Spermatic cord Blood vessels and nerves sphranation Ductus (vas) completes deferens Head of epididymis Testis Efferent ductule Seminiferous tubule Rete testis Lobule Straight tubule Septum Tunica albuginea Body of epididymis Tunica vaginalis Duct of epididymis Cavity of Tail of epididymis tunica vaginalis Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.3c Structure of the testis. Sperm Seminiferous tubule Areolar connective tissue Sustentocyte Interstitial Myoid Spermatogenic endocrine cells cells in tubule cells epithelium Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  27.2 Penis Internally, penis made up of spongy urethra and three cylindrical bodies of erectile tissue, spongy network of connective tissue and smooth muscle with vascular spaces Corpus spongiosum: surrounds urethra and expands to form glans and bulb Corpora cavernosa: paired dorsal erectile bodies Erection: erectile tissue fills with blood, causing penis to enlarge and become rigid Crura: proximal ends of corpora cavernosa surrounded by ischiocavernosus muscle; anchors penis to pubic arch Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.4 Male reproductive structures. Ureter Urinary bladder Ampulla of ductus deferens Prostate Seminal gland Prostatic urethra Ejaculatory duct Orifices of prostatic ducts Bulbo-urethral gland and duct Intermediate part of the urethra Urogenital diaphragm (membranous urethra) Bulb of penis Root of penis Crus of penis Bulbo-urethral duct opening Ductus deferens Corpora cavernosa Epididymis Corpus spongiosum Body (shaft) of penis Testis Section of (b) Spongy urethra Glans penis Prepuce (foreskin) External urethral orifice Dorsal vessels Corpora cavernosa and nerves Urethra Skin Tunica albuginea of erectile bodies Deep arteries Corpus spongiosum Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  Epididymis Head: contains efferent ductules and is located on superior aspect of testis Body and tail located on posterolateral area of testis Duct of the epididymis is ~ 6 m in length – Microvilli (stereocilia) absorb testicular fluid and pass nutrients to stored sperm Nonmotile sperm enter, pass slowly through (~ 20 days), become motile – Can be stored several months During ejaculation, epididymis contracts, expelling sperm into ductus deferens Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  Ductus Deferens and Ejaculatory Duct Ductus deferens (vas deferens) ~ 45 cm long – Passes through inguinal canal to pelvic cavity – Expands to form ampulla – Joins duct of seminal vesicle to form ejaculatory duct Smooth muscle in walls propels sperm from epididymis to urethra Vasectomy: cutting and ligating ductus deferens – Nearly 100% effective form of birth control Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.3a Structure of the testis. Spermatic cord Blood vessels and nerves Ductus (vas) deferens Head of epididymis Testis Efferent ductule Seminiferous tubule Rete testis Lobule Straight tubule Septum Tunica albuginea Body of epididymis Tunica vaginalis Duct of epididymis Cavity of Tail of epididymis tunica vaginalis Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  27.4 Male Accessory Glands Seminal glands – On posterior bladder surface – Contains smooth muscle that contracts during ejaculation – Produces viscous alkaline seminal fluid Fructose, citric acid, coagulating enzyme (vesiculase), and prostaglandins Yellow pigment fluoresces with UV light Comprises 70% volume of semen – Duct of seminal gland joins ductus deferens to form ejaculatory duct Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  27.4 Male Accessory Glands Prostate – Encircles urethra inferior to bladder – Size of peach pit – Consists of smooth muscle that contracts during ejaculation – Secretes milky, slightly acid fluid Contains citrate, enzymes, and prostate-specific antigen (PSA) Plays a role in sperm activation Enters prostatic urethra during ejaculation Makes up one-third of semen volume Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  27.4 Male Accessory Glands – Benign prostatic hyperplasia May be age-related Distorts urethra Treated with surgery, but newer options include: – Using microwaves or drugs to shrink prostate – Balloon compression – Radio-frequency radiation Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  27.4 Male Accessory Glands – Prostate cancer Second most common cause of cancer death in males Digital exam screening, PSA levels – Biopsy if abnormal Treated with surgery and sometimes radiation, castration, drugs In clinical trials: cryosurgery, chemotherapy, ultrasound, proton beam therapy Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  27.4 Male Accessory Glands Bulbo-urethral glands – Pea-sized glands inferior to prostate – Produce thick, clear mucus during sexual arousal Lubricate glans penis Neutralize traces of acidic urine in urethra Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.4 Male reproductive structures. Ureter Urinary bladder Ampulla of ductus deferens Prostate Seminal gland Prostatic urethra Ejaculatory duct Orifices of prostatic ducts Bulbo-urethral gland and duct Intermediate part of the urethra Urogenital diaphragm (membranous urethra) Bulb of penis Root of penis Crus of penis Bulbo-urethral duct opening Ductus deferens Corpora cavernosa Epididymis Corpus spongiosum Body (shaft) of penis Testis Section of (b) Spongy urethra Glans penis Prepuce (foreskin) External urethral orifice Dorsal vessels Corpora cavernosa and nerves Urethra Skin Tunica albuginea of erectile bodies Deep arteries Corpus spongiosum Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  Semen Milky-white mixture of sperm and accessory gland secretions – 2–5 ml semen are ejaculated containing 20–150 million sperm/ml Contains fructose for ATP production, protects and activates sperm, and facilitates sperm movement Alkaline fluid neutralizes acidity of male urethra and female vagina and enhances motility Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  Semen (cont.) Characteristics of semen – Contain prostaglandins that decrease viscosity of mucus in cervix and stimulate reverse peristalsis in uterus – Contains the hormone relaxin and other enzymes that enhance sperm motility – Contains ATP for energy – Can suppress female immune response – Antibiotic chemicals destroy some bacteria – Clotting factors coagulate semen initially to prevent draining out, then liquefy it by fibrinolysin so sperm can finish journey Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  Part 2 – Male Reproductive Physiology 27.5 Male Sexual Response Erection Erection: enlargement and stiffening of penis Arterioles are normally constricted – Sexual excitement causes CNS activation of parasympathetic neurons, which releases nitric oxide (NO) NO release causes relaxation of local vascular smooth muscle Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  Ejaculation Propulsion of semen from male duct system Sympathetic spinal reflex – Bladder sphincter muscle constricts, preventing expulsion of urine – Ducts and accessory glands contract and empty their contents – Bulbospongiosus muscles undergo rapid series of contractions that cause expulsion of semen at ~ 500 cm/s (close to 11 mph) – Ejaculatory event is called climax (orgasm) Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  27.6 Spermatogenesis Spermatogenesis: production of sperm (spermatozoa) in seminiferous tubules Most body cells have 46 chromosomes: – Two sets (23 pairs) of chromosomes One maternal, one paternal: homologous chromosomes Tymmeiosis I Referred to as diploid chromosomal number (2n) _To – Gametes have only 23 chromosomes: haploid chromosomal number (n) Only one member of homologous pair Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.6-1 Comparison of mitosis and meiosis in a mother cell with a diploid number (2n) of 4. Mother cell (before chromosome replication) Chromosome Chromosome replication replication 2n = 4 MITOSIS MEIOSIS Tetrad formed by Replicated Prophase Prophase I synapsis of chromosome replicated homologous chromosomes Chromosomes Tetrads align randomly Metaphase align at the Metaphase I metaphase plate at the metaphase plate Sister chromatids separate during anaphase Homologous chromosomes separate but sister chromatids remain together during anaphase I Daughter unique cells of Daughter cells mitosis of Meiosis I No further chromosomal 2n 2n replication; sister chromatids Meiosis II separate during anaphase II Texact copies n n n n on Daughter cells of meiosis II (usually gametes) Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  Meiosis Compared to Mitosis (cont.) Meiosis I – Reduction division of meiosis: reduces chromosome number from 2n n – Prophase I has events not seen in mitosis or meiosis ffIÉ II Synapsis: homologous chromosomes pair up forming tetrads consisting of 4 chromatids Crossover (chiasmata): exchange of genetic material between male and female chromatids – Results in unique chromosomes that are mixtures of maternal and paternal chromosomes Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.8 The independent assortment of homologous chromosomes in meiosis. Possibility 1 synapsis Possibility 2 tetrad Two equally probable arrangements of chromosomes at metaphase I homologous Chromosomes Metaphase II Daughter cells Combination 1 Combination 2 Combination 3 Combination 4 Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.7-1 Meiosis. Interphase cell MEIOSIS I Chiasmata Prophase I Nuclear Centromere Prophase events occur, as in mitosis. Additionally, synapsis envelope Crossover occurs: Homologous chromosomes come together along their length to form tetrads. During synapsis, the “arms” of Centriole Spindle homologous chromatids pairs wrap around each other, forming several crossovers. Sister The nonsister chromatids trade segments at points chromatids of crossover. Crossover is followed through the diagrams below. Chromatin Nuclear envelope fragments late 2n = 4 in prophase I Interphase events As in mitosis, meiosis is preceded by DNA replication and other Metaphase I preparations for The tetrads align randomly on the spindle cell division. equator in preparation for anaphase. homologous marked Tetrad Dyad Anaphase I angems Unlike anaphase of mitosis, the centromeres do not separate during anaphase I of meiosis, so the sister chromatids (dyads) remain firmly attached. However, the homologous chromosomes do separate from each other and the dyads move toward opposite poles of the cell. Chromosomes uncoil Telophase I The nuclear membranes re-form around the chromosomal Nuclear masses, the spindle breaks down, and envelopes the chromatin reappears as telophase and cytokinesis end. The re-form 2 daughter cells (now haploid) enter a second interphase-like Cleavage period, called interkinesis, before meiosis II occurs. There is no furrow second replication of DNA before meiosis II. Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  looks just like mitosis Figure 27.7-2 Meiosis. MEIOSIS II Prophase II Meiosis II begins with the products of meiosis I (2 haploid daughter cells) and undergoes a mitosis-like nuclear division process referred to as the equational division of meiosis. Metaphase II Effmatias Anaphase II After progressing through the phases of meiosis and cytokinesis, the product is 4 haploid cells, each genetically different from the original Telophase II mother cell. (During human and cytokinesis spermatogenesis, the daughter cells remain interconnected by cytoplasmic extensions during the meiotic phases.) Products of meiosis: haploid daughter cells Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.7 Meiosis. Interphase cell MEIOSIS I Prophase I Nuclear Centromere Prophase events occur, as in mitosis. Additionally, synapsis Crossover occurs: Homologous chromosomes come together along envelope their length to form tetrads. During synapsis, the “arms” of Centriole Spindle homologous chromatids pairs wrap around each other, forming several crossovers. Sister The nonsister chromatids trade segments at points chromatids of crossover. Crossover is followed through the diagrams below. Chromatin Nuclear envelope 2n = 4 fragments late in prophase I Interphase events As in mitosis, meiosis is preceded by DNA replication and Metaphase I other preparations for cell The tetrads align randomly on the spindle equator division. in preparation for anaphase. Tetrad Dyad Anaphase I Unlike anaphase of mitosis, the centromeres do not separate during anaphase I of meiosis, so the sister chromatids (dyads) remain firmly attached. However, the homologous chromosomes do separate from each other and the dyads move toward opposite poles of the cell. Chromosomes uncoil Telophase I The nuclear membranes re-form around the chromosomal Nuclear masses, the spindle breaks down, and envelopes the chromatin reappears as telophase and cytokinesis end. re-form The 2 daughter cells (now haploid) enter a second interphase- Cleavage like period, called interkinesis, before meiosis II occurs. There is no second replication of furrow DNA before meiosis II. MEIOSIS II Prophase II Meiosis II begins with the products of meiosis I (2 haploid daughter cells) and undergoes a mitosis-like nuclear division process referred to as the equational division of meiosis. Metaphase II i Anaphase II After progressing through the phases of meiosis and cytokinesis, the product is 4 haploid cells, each genetically different from the original Telophase II mother cell. (During human and cytokinesis spermatogenesis, the daughter cells remain interconnected by cytoplasmic extensions during the meiotic phases.) Products of meiosis: haploid daughter cells Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.  Bioflix: Meiosis L Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.9a Spermatogenesis. A type iii iii throws sperm C Scanning electron micrograph of a cross- sectional view of a seminiferous tubule (165×) lumen with sperm flagella Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.9b Spermatogenesis. outerpart of seminiferous trove Basal lamina A go Spermatogonium 2n 2n Type A daughter cell Type ypeB gothrough (remains at basal lamina through mitosis (stem cell) as a precursor cell) Mitosis 2n Type B daughter cell meiosis t Growth Enters make more manesperm Type B meiosis I and moves to 2h (early spermatogenesis) adluminal 2n Primary compartment spermatocyte In.mn Meiosis I Meiosis completed on n n Secondary Spermatogenesis spermatocytes Meiosis II n n n n Early spermatids n n n n Late spermatids towards (late spermatogenesis) Spermiogenesis primaryspengffel n n n n fstffffe.hr Spermatozoa me uo.s seo0hamyou Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Shirin Events of spermatogenesis, showing the relative position of various spermatogenic cells Figure 27.9c Spermatogenesis. Tight junction between sustentocytes Spermatogonium (stem cell) Cytoplasm of adjacent Sustentocyte sustentocytes nucleus Basal lamina Type A daughter cell (remains at basal lamina Basal compartment as a precursor cell) Type B daughter cell Primary spermatocyte Secondary spermatocytes Early spermatids Adluminal compartment Late spermatids Cytoplasmic bridge Lumen of seminiferous Spermatozoa tubule A portion of the seminiferous tubule wall, showing the spermatogenic cells surrounded by sustentocytes (colored gold) Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.10 Spermiogenesis: transformation of a spermatid into a functional sperm. Approximately 24 days Golgi apparatus Acrosomal Mitochondria vesicle Acrosome Nucleus 1 2 Spermatid Centrioles Microtubules nucleus Midpiece Head 3 Flagellum Excess cytoplasm 4 Tail 5 6 7 Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Spermatogenesis: Summary of Events in the Seminiferous Tubules (cont.) Tight junctions form blood testis barrier – Prevents sperm antigens from escaping into blood and causing activation of immune system – Sperm is not formed until puberty, so it is absent during immune system development Results in sperm not being recognized as “self” Therefore, sperm needs to be kept separated from rest of body to avoid being attacked by immune system – Spermatogenesis takes 64–72 days if conditions are hospitable – Sperm are unable to swim, but pressure of testicular fluid pushes immotile sperm into epididymis, where they gain motility and fertilizing power Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Figure 27.11 Hormonal regulation of testicular function, the hypothalamic-pituitary-gonadal (HPG) axis. 1 GnRH Anterior Via portal pituitary blood 7 6 Inhibin 2 FSH LH Interstitial endocrine 3 4 cells Testosterone Somatic and Sustentocyte 5 psychological effects at other body sites; maintenance Spermatogenic of secondary sex ABP cells characteristics Seminiferous tubule Stimulates Bio 202 ASU DPC T. Penkrot Inhibits © 2016 Pearson Education, Inc. Figure 27.12 Plasma testosterone and sperm production levels versus age in male humans. Sperm production (% of maximal) Adult Plasma testosterone level Fertilization Birth 100 Puberty 50 0 3 6 9 1 10 20 60 Months Years Bio 202 ASU DPC T. Penkrot Age © 2016 Pearson Education, Inc.  Mechanism and Effects of Testosterone Activity Testosterone, synthesized from cholesterol, is transformed at some target cells – Converted to dihydrotestosterone (DHT) in prostate and estradiol in some brain neurons – Prompts spermatogenesis and targets all accessory organs – Has multiple anabolic effects throughout body Deficiency leads to atrophy of accessory organs, semen volume declines, and erection/ejaculation are impaired; treatment: testosterone replacement Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc. Mechanism and Effects of Testosterone Activity (cont.) Male secondary sex characteristics: features induced in nonreproductive organs by male sex hormones (mainly testosterone) – Appearance of pubic, axillary, and facial hair – Enhanced growth of chest hair; deepening of voice – Skin thickens and becomes oily – Bones grow, increase in density – Skeletal muscles increase in size and mass – Boosts basal metabolic rate – Basis of sex drive (libido) in males Bio 202 ASU DPC T. Penkrot © 2016 Pearson Education, Inc.