Human Fetal Development PDF

HUMAN FOETAL DEVELOPMENT [email protected]  PART 1 ❖ to briefly describe fertilisation, cleavage stage, and implantation ❖ to briefly describe gastrulation, organogenesis, and neurulation 1. the CAPACITATION change undergone by sperm in...

HUMAN FOETAL DEVELOPMENT [email protected]  PART 1 ❖ to briefly describe fertilisation, cleavage stage, and implantation ❖ to briefly describe gastrulation, organogenesis, and neurulation 1. the CAPACITATION change undergone by sperm in & FERTILIZATION the female reproductive tract 2. CLEAVAGE AND IMPLANTATION rapid cell division in oviduct Day 3 - 4, Morula is formed. Blastomere dividing and secrete fluid in the centre, forming a Day 6 – 7, inner cell mass is cavity called blastocoel. formed. Blastocyst cavity then separated to two; At this stage, embryo is a hollow ball of cells called 1. Trophoblast *part of the blastula. placenta 2. Embryoblast *inner cell mass that develops into foetus  2. CLEAVAGE AND IMPLANTATION on uterine wall Blastocyst burrows into the implantation site Week 2 Trophoblast differentiates, into two layers: 1. Cytotrophoblast *specialized epithelial cells 2. Syncytiotrophoblast *multinucleated layer Embryoblast differentiates into, 1. Hypoblast Forms the extraembryonic yolk sac 2. Epiblast Gives rise to the embryo’s tissues  3. GASTRULATION Week 3 a migration of blastocyst inward, leading to multiple distinct layers of tissue called germ layers From bilaminar disk into a trilaminar structure, called gastrula How it begin? Epiblast cells migrate toward the primitive streak, become flask-shaped, detach and slip beneath it Once invaginated (inward movement) Hypoblast displaced, creating endoderm Other cells lie between epiblast, creating ectoderm and mesoderm Three germ layers; 1. Ectoderm give rise to nervous system, epidermis, and neural crest-derived tissues 2. Mesoderm give rise to notochord, axial skeleton, cartilage, connective tissue, trunk muscles, kidneys, and blood 3. Endoderm give rise to gastrointestinal, respiratory, urinary systems, and endocrine glands  ORGANOGENESIS Week 3-8 a process of three germ layers develop into the internal organs and tissues of the organism NEURULATION Day 17 – Week 4 the formation of a neural tube Gives rise to the brain and the spinal cord, forming central nervous system  PART 2 ❖ to identify the structures of extra-embryonic membrane ❖ to distinguish the general functions of each of the structures EXTRA-EMBRYONIC MEMBRANES Enveloped set for the foetus on the uterine endometrial layer, consisting; Chorion –outermost membrane, surround the embryo ▪ Formed from layers of trophoblast and extra-embryonic mesoderm ▪ Finger-like extensions of chorionic villi develop, penetrate into uterine tissue to Allow exchange of gas, blood, and waste of the embryo with the mother’s circulatory system ▪ Later develops into placenta  5 main functions: Protection: cushion/absorb shocks Temperature control: helps regulate the foetus’s temperature Movement: allows the foetus movement for musculoskeletal development and blood flow Exchange of substances: allows exchange of oxygen between the Amnion sac –completely umbilical cord and the foetus surrounds the embryo, secretes amniotic fluid ▪ Formed from the combination of ectoderm and mesoderm ▪ Thin, transparent membrane Allantois ▪ Originated from the yolk sac ▪ Small vascularized sac Yolk Sac –membrane connects with midgut ▪ Small, membranous structure helps form the umbilical blood produces nourishment, helps circulate vessels and urinary bladder gasses, and produce cells that develop into the umbilical cord, blood cells, and stores urinary waste and helps reproductive organs exchange nutrients and gas Placenta –vital link between maternal and embryonic systems ▪ Fetal portion with chorionic villi ▪ Maternal portion consists of endometrium area- decidua basalis for nutrient and gas exchange, hormone production, immunity, protection, implantation Umbilical Cord –oval area on the embryo’s ventral surface ▪ Connecting cord between embryo and placenta, supplies oxygenated, nutrient-rich blood ▪ Conversely, the umbilical arteries return the deoxygenated, nutrient- depleted blood  PART 3 ❖ to describe the gestation and hormone involved ❖ to describe parturition, the hormone involved, and positive feedback mechanisms ❖ to describe lactation, and the hormone involved GESTATION The period of pregnancy  HORMONES involved Human chorionic gonadotropin (hCG) produced in the placenta –pregnancy hormone, can be used to diagnose some types of cancer Progesterone produced by the ovary and placenta –stimulate the thickening of the uterine lining Oestrogen produced by the ovary and placenta –helps maintain a healthy pregnancy  Human placental lactogen (hPL) produced by the placenta –helps provide nutrition to the foetus, plays role in stimulation milk gland in the breasts Oxytocin Responsible for uterine contraction and stop heavy bleeding during/after during childbirth, helps deliver placenta PARTURITION The process of childbirth POSITIVE FEEDBACK MECHANISMS HORMONES involved  LACTATION HORMONES involved By causing the contraction of breast- myoepithelial cells The smooth muscle–like cells, expel milk from alveoli into ducts and sub- areolar sinuses that empty through a nipple pore.  HUMAN REPRODUCTIVE SYSTEM Norfarahin Norwen | [email protected]  Gametes are produced in special paired glands: i. Male sperm in the testes ii. Female ova in the ovaries The gonads are primary sexual organs Both gonads are associated with a system of ducts and accessory glands known as secondary sexual organs  PART I ❖ to identify the male and female reproductive structures ❖ to distinguish the general functions of each of the reproductive structures ❖ to demonstrate reproductive issues in both gender  What comes to your mind when you hear “human reproductive structures and its general function” Padlet link: https://padlet.com/nnorfarahin/human-reproductive-system-ukle7o8jth7aee48 Seminiferous tubule  Male Reproductive Structures Seminiferous tubule.  External reproductive organs 1. Penis –conveys urine and semen through urethra Cylindrical, conical-shaped, divided into three regions; Root –located in the perineal body of the pelvic floor, contains 3 erectile tissues; 2 crura and 1 bulb and 2 muscles; ischiocavernosus and bulbospongiosus Body –located between the root and glans, composed of 3 cylinders of erectile tissues; 2 corpora cavernosa and 1 corpus spongiosum Glans –formed from expansion of the corpus spongiosum External reproductive organs 2. Scrotum –protects testicles, regulates temperature, sexual arousal Pouch-shaped, covers by sparse hairs, consists of thick skin and muscle; Dartos smooth muscle acts to wrinkle the scrotal skin by contraction and relaxation Cremaster muscle acts to elevate the testes toward the body by raises or lowers Internal reproductive organs 1. Testes –sperm and testosterone hormone production Oval-shaped, enclosed with two tunics; Tunica vaginalis and tunica albuginea with septa extend inward Wedge-shaped lobule with highly coiled of seminiferous tubules, specific site for meiosis Each tubule is lined by germinal epithelium which is made up of Sertoli cells and Seminiferous male tubule germ cells 2. Epididymis – 1. controls the composition of the fluid produced by the seminiferous tubules 2. absorbs and recycles damaged protozoa and cellular debris 3. stores, protects, and facilitates spermatozoa and its functional maturation Cup-shaped, coiled and twisted structures Head contains efferent ductules with following regions of caput, corpus, and cauda 3. Vas deferens –transport Sac-liked structures lying on the for mature sperm posterior bladder surface Muscular tubes, part of the spermatic cord 4. Seminal Vesicle – 1. secretes slightly alkaline-yellowish and viscous fluid, helps to regulate the pH of the tubular 2. contains fructose, provides energy to sperm cells 3. contains prostaglandins, stimulates muscular contractions within uterus End behind the urinary bladder, uniting with 4. contains citric acid and coagulating seminal vesicle duct just enzyme known as vesiculase Seminiferous outside the prostate gland tubule  5. Prostate gland – 1. contracts during ejaculation, secreting milky slight-acidic fluid to enhance sperm motility 2. prostatic fluid contains citrate, for sperm nourishment 3. plays a role in hormone production and helps in regulating urine flows Chestnut or doughnut-shaped, muscular structure surrounded by a thick connective tissue capsule Seminiferous tubule 6. Bulbourethral glands / Cowper’s glands / Mery glands – secreting a thick, clear mucous- like fluid and response to sexual stimulation neutralizer to urine acidity fluid lubricates penis end for sexual intercourse  Reproductive issues in men 1. Sperm abnormalities Azoospermia – No sperm production Teratospermia – Oligospermia – Sperm morphology problems Few sperm production Leukocytospermia / Pyospermia – High concentration of white blood cells in semen Asthenospermia – Sperm motility problems 2. Structural– Testes Scrotum Cryptorchidism, testicular torsion Scrotal swelling, testicular / cancer, orchitis, hydrocele, trauma varicocele, epididymo-orchitis Vas Deference and Spermatic Cord Epididymis Obstructive azoospermia, Epididymitis, spermatocele congenital absence of the vas deferens (CAVD), spermatic Prostate gland cord torsion Prostatitis, benign prostatic hyperplasia, prostate cancer 3. Hormonal and Genetic Disorders– Klinefelter syndrome Penis Hypogonadism Erectile dysfunction, peyronie’s Androgen insensitivity syndrome disease, phimosis, paraphimosis, priapism, penile cancer  Female Reproductive Structures Seminiferous tubule.  External reproductive organs/structures 1. Mons pubis – rounded mass of fatty tissue covered by skin and hair serve as a cushion for pubic bones 2. Labia majora – large, fleshy folds of tissue enclose and protect the other external genital organs 4. Clitoris – small nub of flesh at the top contain sweat, oil-secreting of vulva, covers by a fold of skin glands called the prepuce for lubricating secretions sexual arousal / orgasm and protection against injury 3. Labia minora – small, folds of skin surround vaginal opening 5. Vaginal opening act as protection, for sexual function, for shock absorption, for menstruation, sexual and aid in urination intercourse, and childbirth  Internal reproductive organs/structures 4. Fallopian Tube ovaries-uterus connection 1. Vagina –mascular canal, lined with mucous membranes for moisture for fertilization, by finger-like 2. Cervix –hold in the middle structures of fimbriae catches allows sperm to enter, menstrual egg(s) into the tube blood to exit, and cervix dilation for vaginal childbirth 5. Ovary –small, oval-shaped, located at side of uterus 3. Uterus –pear-shaped, divided into For eggs and hormones two parts; the cervix and the corpus production holds foetus during pregnancy  Reproductive issues in women Structural– Vagina Ovary Vaginitis, vaginal atrophy / PCOS, premature ovarian prolapse / septum / cancer insufficiency, ovarian cysts / torsion / cancer Cervix Cervicitis, cervical dysplasia / Fallopian tube cancer/ insufficiency / polyps Salpingitis, ectopic pregnancy, hydrosalpinx, tubal factor Uterus infertility / cancer Endometriosis, adenomyosis, uterine fibroids / prolapse / cancer  PART II ❖ to explain spermatogenesis in male ❖ to explain oogenesis and menstrual cycle in female ❖ to differentiate roles of male and female hormones involved in the system  SPERMATOGENESIS Hypothalamus secreting GNRH to stimulate the pituitary gland gonadotropin-releasing hormone  1. follicle-stimulating hormone (FSH) stimulate Sertoli cells spermatogenesis begin 2. luteinizing hormone (LH) Leydig cells stimulate testosterone secretion Step 1: Mitosis Germinal cell (diploid, 2n=46) → mitotic cell divisions → Spermatogonia (diploid, 2n=46) Spermatogonia grow into larger cells with more cytoplasm called Primary spermatocyte (diploid, 2n=46) Step 2: Meiosis Primary spermatocyte undergo Meiosis I → Secondary spermatocytes (haploid, n=23) Secondary spermatocytes undergo Meiosis II → Spermatids an immature sperm cells (haploid, n=23) Step 3: Spermiogenesis Spermatids → spermatozoa with mature, motile spermatozoa, which then detached from Sertoli cells → lumen Phase 4: Capacitation Why men needs testosterone? OOGENESIS production of ova Before birth, Phase 1: Multiplication Primordial follicles (diploid, 2n=46) → mitotic cell divisions → many diploid oogonia (diploid, 2n=46) 1(A): Growth Oogonia grow into larger cells with more cytoplasm called Primary oocytes (diploid, 2n=46) continues until Prophase I of Meiosis I  When puberty is reached, 1. follicle-stimulating hormone (FSH) stimulate Follicle Granulosa cells for ovulation for progesterone secretion 2. Luteinizing hormone (LH) Theca cells for oestrogen secretion  Phase 2: Maturation FSH stimulates to continue Meiosis I, producing: 1. 1st Polar body –degenerate 2. Secondary oocyte –survive and continues until Metaphase II of Meiosis II NO fertilisation –no further development. If fertilisation happen –Meiosis II will be completed MENSTRUAL CYCLE development of uterine lining Follicular phase Day 1-6: stimulation of FSH and LH develop many primary ovarian follicles, one become larger → Graafian follicle Day 7-13: all the growing follicles release oestrogen, stimulating proliferation of the uterus endometrium Luteal phase Ovulation phase Day 16-28: Yellowish fat Day 14: oestrogen trigger further release globules of luteal cells are of LH, weaken the ovarian wall deposited, and form the corpus luteum, which producing Mature Graafian follicle rupture and progesterone for uterus release an ovum (secondary oocyte) preparation 1. IF pregnancy OCCURS 2. IF pregnancy DOES NOT OCCURS Corpus luteum Progesterone Corpus luteum Progesterone Endometrium of inner wall of the uterus sheds →bleeding  Roles of hormones Oestrogen Keep periods regular, plays a role in ovulation Thins cervical mucus, keeps vaginal walls thick, elastic and lubricated Thickens the lining of uterus endometrium for pregnancy Low oestrogen – High oestrogen – Anorexia nervosa Obesity Osteoporosis Polycystic ovary syndrome Uterine fibroids and polyps, grows of Irregular periods noncancerous tumors in uterus Vaginal atrophy Uterine cancer, build up of uterus Female sexual dysfunction lining may cause grow of cancer cells Fluctuating oestrogen – Infertility Endometriosis, may worsen the pain Breast cancer, it does not increase the risk but worsen once its formed Progesterone Regulates menstruation bleeds Create healthy environment for endometrium of uterus lining Thickens the cervical mucus to prevent sperm and bacteria from entering uterus Fluctuating of progesterone – Mood changes Headaches, migraine, trouble sleeping Hot flashes / vasomotor symptoms Irregular menstrual period Difficulty in conceiving, miscarriage, early labor, ectopic pregnancies