Week 19 PHA112 Reproductive System 2023-24 Student Handout PDF

WEEKS 19 MPharm Programme Reproductive System 1 &2 Dr Praveen Bhugra PHA112 2022-23 Slide 1 of 25 PHA112 Reproductive System 1 &2 WEEKS Learning Objectives 19 From this lecture you should be able to:  Understand and explain briefly the sexual differentiation including an overview of the...

WEEKS 19 MPharm Programme Reproductive System 1 &2 Dr Praveen Bhugra PHA112 2022-23 Slide 1 of 25 PHA112 Reproductive System 1 &2 WEEKS Learning Objectives 19 From this lecture you should be able to:  Understand and explain briefly the sexual differentiation including an overview of the chromosomal distribution and inheritance of the gender.  Understand and explain in detail male reproductive system including the organs, structure, location and function of the testes, system of ducts (epdidymis, ductus deferens, ejaculatory ducts & urethra), accessory glands (seminal vesicles, prostate, bulbourethral glands) and several supporting structures including scrotum & penis. Slide 2 of 25 PHA112 Reproductive System 1 &2 WEEKS Learning Objectives 19 From this lecture you should be able to:  Understand and describe in detail the male reproductive physiology including • Secretions that pass into the spermatic fluid • Process of ejaculation • Changes occurring at puberty in male including spermatogenesis • Hormonal control and functions of the male reproductive hormones Slide 3 of 25 PHA112 Reproductive System 1 &2 WEEKS Introduction 19 • Reproduction – Union of male and female gametes (reproductive or germ cells) – Each with half set of chromosomes, to form new individual with full, unique set of chromosomes • All body systems are essentially identical in male and female except reproductive system – Union of genetic material from two sexual partners – Female system is equipped and nourish the offspring to a point at which it can survive independently in the external environment Slide 4 of 25 PHA112 Reproductive System 1 &2 WEEKS Chromosomal Distribution 19 • Human somatic cells have 46 chromosomes – 22pairs of somatic chromosomes – One pair of sex chromosomes • Sex chromosomes identified as X and Y • Female genotype XX and Male XY • Ovary contribute X chromosomes • Sperm contribute either X or Y chromosomes Slide 5 of 25 PHA112 Reproductive System 1 &2 WEEKS 19 Overview of chromosomal distribution (sexual reproduction) Parents with diploid (46 chromosomes) somatic cells Mother Father Meiotic division of germ cells Meiotic division of germ cells Haploid (23 chromosomes) ovum Haploid (23 chromosomes) sperm Fertilization Diploid (46 chromosomes) fertilized ovum Mitosis Offspring with diploid (46 chromosomes) somatic cells Slide 6 of 25 PHA112 Reproductive System 1 &2 WEEKS Inheritance of the Gender 19 Mother Father XX XY Meiotic division Sex cells X X X Fertilisation X Y X XX XY X XX XY Chance of a girl 50% Chance of a boy 50% Slide 7 of 25 PHA112 Reproductive System 1 &2 Y Possible children WEEKS Male Reproductive System 19 Seminal vesicle Urinary bladder Rectum Ejaculatory duct Ductus (vas)deferens Anus Prostate Bulbourethral gland Epididymis Penis Urethra Scrotum Testis • Organs: testes, ducts, glands & supporting structures • Ducts: epdidymis, ductus deferens, ejaculatory ducts & urethra • Glands: seminal vesicles, prostate, bulbourethral glands • Supporting structures: scrotum & penis Slide 8 of 25 PHA112 Reproductive System 1 &2 Male Reproductive System WEEKS 19 1. The testes produce sperm and the male sex hormone testosterone 2. The ducts transport, store and assist in maturation of sperms 3. The accessory sex glands secrete most of the liquid portion of the semen 4. The penis contains the urethra, a passageway for ejaculation of semen and excretion of urine Slide 9 of 25 PHA112 Reproductive System 1 &2 WEEKS 19 Scrotum • Sac of loose skin, fascia & Spermatic cord Internal oblique muscle smooth muscle (dartos muscle) divided into two pouches by a Cremaster muscle septum • Pouch that supports the testes Autonomic nerve • Septum separates into separate Testicular artery sections for each testis Scrotal Testicular vein • Sperm requires temperatures 2- septum 3°C below body temperature Lymphatic vessels • Allows raising and lowering Dartos muscle testes to adjust temperature Skin of Raphe • Cremaster muscle -small skeletal scrotum muscle bands; descend as extension of spermatic cord to surround the testes Slide 10 of 25 PHA112 Reproductive System 1 &2 WEEKS Testes 19 • Paired oval glands • Develop on embryo’s posterior wall and descend into scrotum –Starts in 7th month • The testis performs two important functions • Production of sperm – male gametes which carry generic material and can fertilize an egg • Secretion of steroid hormones - testosterone (normal sperm production and full masculine development ) Slide 11 of 25 PHA112 Reproductive System 1 &2 WEEKS Internal Structure of Testis 19 • Testis divided internally into 250-300 lobules(segments) • Each lobule consists of 2-3 coil tubes – Seminiferous tubules • At the apex each lobule, the tubules join and pass into straight tube – tubuli recti and then into coiled epididymis • Together the tubli recti form – rete testis Slide 12 of 25 PHA112 Rete testis Reproductive System 1 &2 WEEKS 19 Internal Structure of Testis (seminiferous tubules ) • Outer smooth muscle - contract to move the sperm and fluid through the tubule • Inner epithelial cell layer (SertoIi cells) - controlling the formation and development of sperm • Lumen of tubule filled with fluid - medium for development • Between the tubules lies connective tissue – supports the tubules and contains clusters of Leydig cells (interstitial cells of Leydig) • Leydig cells – synthesis and secretion of testosterone and other androgens Slide 13 of 25 PHA112 Reproductive System 1 &2 WEEKS 19 Internal Structure of Testis (seminiferous tubules ) {Sertoli Cells and Spermatogenic cells} • Sertoli cells – extend from the basement membrane to lumen • Form blood –testis barrier • Isolate the developing gametes from blood • Prevents an immune response against the spermatogenic cell’s surface antigens • Support and protect developing spermatogenic cells • Release of sperms into the lumen • Secrete hormone inhibin and regulate the effects of testosterone and follicle – stimulating hormone (FSH) Slide 14 of 25 PHA112 Reproductive System 1 &2 WEEKS 19 Internal Structure of Testis (seminiferous tubules ) {Sertoli Cells and Spermatogenic cells} Slide 15 of 25 PHA112 Reproductive System 1 &2 Spermatogenesis WEEKS 19 • Spermatogium with 2n=46 chromosomes multiply by mitosis • Primary spermatocyte with 2n=46 chromosomes • First meiosis division give two secondary spermatocytes, each with 23 chromosomes that become double stranded. • Second meiosis division give four spermatids, each with 23 single stranded chromosomes • Each of four spermatids develop into a sperm Slide 16 of 25 PHA112 Reproductive System 1 &2 Spermatozoa Structure (Sperm Morphology) WEEKS 19 • ~300 million /day Life time • ~ 48 hours in female tract • Adapted for reaching and fertilizing the egg • Head contains DNA and the acrosome with enzymes for penetrating the egg • Middle contains mitochondria to form ATP for energy • Tail is flagellum used for locomotion Slide 17 of 25 PHA112 Reproductive System 1 &2 Male Sex Hormones WEEKS 19 • The male sex hormones are androgens . • Testosterone the primary male sex hormone is an androgen • Mainly Leydig cells of the testes and to a lesser extent the adrenal glands produce testosterone and other androgen • In men, sex hormone production is relatively constant with some diurnal variation • Responsible foetal differentiation and development of male urogenital system and have some effects on brain • After birth Leydig cells become quiescent until activated by gonadotropins during puberty • At puberty androgens cause the sex organs to grow and secondary sex characteristics to develop Slide 18 of 25 PHA112 Reproductive System 1 &2 WEEKS 19 Slide 19 of 25 Hormonal Control PHA112 Reproductive System 1 &2 Effects of Testosterone in Male WEEKS 19 • Required for initiation and maintenance of spermatogenesis • Decrease GnRH secretion via action of hypothalamus • Inhibit LH secretion via a direct action on the anterior pituitary gland • Induce differentiation of male accessary reproductive organs and maintains their function • Induces male secondary sex characteristics; opposes action of oestrogen on breast growth • Stimulates protein anabolism, bone growth and cessation of bone growth • Required for sex drive and may enhance aggressive behaviour • Stimulates erythropoietin secretion by the kidneys Slide 20 of 25 PHA112 Reproductive System 1 &2 Accessory Sex Glands WEEKS 19 Prostate Secretes 30% of milky, slightly acidic seminal fluid with an antibiotic to kill bacteria Seminal Vesicles Secrete 60% of clear, alkaline seminal fluid, with fructose sugar, ATP and prostaglandins for normal sperm nutrition & function Chemicals for coagulation of semen Bulbourethral glands (Cowper’s Glands) Secrete clear, alkaline mucus to buffer and lubricate urethra Slide 21 of 25 PHA112 Reproductive System 1 &2 WEEKS Penis 19 • Contains urethra- root, body & glans penis – Passage for semen and urine • Penis has three columns of erectile tissue – Two dorsal columns called corpora cavernosa – One ventral column surrounding urethra called corpus spongiosum • Glans penis—distal end of penis – Covered by foreskin (prepuce) – Surgical removal of foreskin called circumcision Slide 22 of 25 PHA112 Reproductive System 1 &2 Semen WEEKS 19 • Mixture of sperms and seminal fluid • 60% from seminal vesicles, 30% from prostate , 10% from bulbourethral glands • Slightly alkaline, milky appearance and sticky • Contains nutrients, clotting proteins & an antibiotic to protect the sperms • Typical ejaculate is 2.5 to 5 ml in volume • Normal sperm count is 50 to 150 millions/mL – Actions of many sperm are needed for one to enter – If less than 20 millions/mL - sterile Slide 23 of 25 PHA112 Reproductive System 1 &2 Factors contributing to ejaculation of functional sperms WEEKS 19 A sperm travels from their site of production in the testes to the exterior, the sequence of the ducts through which they will pass rete testis ; efferent ductules; epididymis; vas deferens; ejaculatory duct; prostatic urethra; penile urethra Slide 24 of 25 PHA112 Reproductive System 1 &2 WEEKS 19 Further Reading refer to the following textbooks • Ross and Wilson Anatomy and Physiology in Health and illness 13th Edition • Gerard J. Tortora and Byran H. Derrickson Principles of Anatomy and Physiology 13th Edition • Frederic H. Martini Fundamentals of Anatomy & Physiology 7th Edition • Lauralee Sherwood Human Physiology From Cells to Systems 7th Edition • Robert G. Carroll Elsevier’s Integrated Physiology Slide 25 of 25 PHA112 Reproductive System 1 &2