2024 Human Foetal 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.