Lesson+15-23_Embryology 2.pptx

Lessons 15-23 Embryology Human Anatomy and Embryology Prof. Mar Ubero Dentistry Index CONTENT -Embryology. -Gametogenesis. -First week of development: -Fertilisation. -Cleavage. -Implantation. -Second week of development. -Third week of development. -Fourth week of development. Derivatives. E...

Lessons 15-23 Embryology Human Anatomy and Embryology Prof. Mar Ubero Dentistry Index CONTENT -Embryology. -Gametogenesis. -First week of development: -Fertilisation. -Cleavage. -Implantation. -Second week of development. -Third week of development. -Fourth week of development. Derivatives. Embryology 1. Embryology Embryogenesis Organogenesis Foetal period Period of functional maturation Langmann´s medical embryology. 13th Ed. 2. Gametogenesis OOGENESIS 2. Gametogenesis OOCYTE Nucleu s Cytoplas m (Avoids polyspermy) Pellucid zone (nutrition and protection) Corona radiata Haploid: 23 chromosomes SPERMATOGENESIS 2. Gametogenesis Langmann´s medical embryology. 13th Ed. SPERMATOGENESIS 2. Gametogenesis Spermatozoon Acrosome Head Nucleus Neck Tail Nº of follicles: 2. Gametogenesis 7 mill. follicles (foetus) - Each month: 15-20 follicles begin to mature. - Only one reaches full maturity: Graafian follicle. - The others degenerate (atretic). 600.000 (new born) 40.000 (beginning of puberty) 400-500 (will be ovulated) Menarche/Menopause Ovarian cycle 2. Gametogenesis Non fertilized oocyte degenerates 2 Oviduc t Uteru Ovar s y Endometri 3 um Vagina Langmann´s medical embryology. 13 Ed. th 1. Follicular phase: Fast growing and maturation of ONE follicle (Graafian follicle). 2. Ovulation: oocyte is extruded from the ovary. 3. Luteal phase: the ruptured follicle starts developing a yellowish pigment and changes into the Corpus luteum (which secretes Menstrual bleeding 4 Oocyte 1 Ovarian cycle 2. Gametogenesis Langmann´s medical embryology. 13th Ed. FERTILIZATION 3. First week of development Langmann´s medical embryology. 13th Ed. FERTILIZATION 3. First week of development Langmann´s medical embryology. 13th Ed. Process by which male and female gametes fuse FERTILIZATION 3. First week of development Langmann´s medical embryology. 13th Ed. FERTILIZATION 3. First week of development Langmann´s medical embryology. 13th Ed. CLEAVAGEFrom zygote to blastocyst 3. First week of development 1st day 2 blastomeres 2nd day 4 blastomeres 3rd day - MORULA 16-32 blastomeres 2-cell stage 8-cell stage 4-cell stage Morul a 4th day - BLASTOCYST 2 cellular masses blastocyst (early) Blastocyst - Series of mitotic divisions, increasing the number of cells without increasing the size. - These cells which become smaller with each cleavage division, are known as blastomeres. CLEAVAGE 3. First week of development Inner cells of the morula constitute the inner cell mass, and surrounding cells compose the outer cell mass. The inner cell mass gives rise to tissues of the embryo proper, and the outer cell mass forms the trophoblast, which later contributes Zona pellucida to the placenta. Embryoblast Blastocele Trophoblast Schoenwolf GC, Bleyl SB, Brauer PR, Francis-West PH. Larsen's Human Embryology. 6th Ed. Elsevier, 2021. IMPLANTATION 3. First week of development Endometrium Implantation is a simultaneous process to the development of the bilaminar germ disc. A B C C’ - By the end of the first week of development, the human zygote has passed through the morula and blastocyst stages and has begun implantation in the uterine mucosa. - The zona pellucida has disappeared, allowing implantation to begin. In the human, trophoblastic cells over the embryoblast pole begin to penetrate between the epithelial cells of the uterine mucosa on about the sixth day. A) Apposition (approximation). B) Adhesion. D C-C’) Invasion (6th day). D) Placental circulation (14th day). IMPLANTATION 3. First week of development Langmann´s medical embryology. 13th Ed. Figure shows a schematic representation of a blastocyst at the sixth day of development showing trophoblast cells at the embryonic pole of the blastocyst penetrating the uterine mucosa. The human blastocyst begins to penetrate the uterine mucosa by the sixth day of development. BILAMINAR GERM DISC 4. Second week of development Formation of the bilaminar germ disc is a simultaneous process to implantation, wherein the embryoblast differentiates into both the epiblast and hypoblast. Langmann´s medical embryology. 13th Ed. BILAMINAR GERM DISC 4. Second week of development Syncytiontrophoblast 9th day 8th day Cytotrophoblast Hypoblas t Epiblast Blastocyst is partially Blastocyst is more deeply embedded in the embedded in the endometrium. endometrium. Day 8: Trophoblast has differentiated into 2 layers: cytotrophoblast and syncytiotrophoblast. Embryoblast into hypoblast and epiblast Amniotic cavity BILAMINAR GERM DISC 4. Second week of development Primitive yolk sac (exocoelomic cavity) Will give rise to the digestive tube. 11th day Extraembryonic mesoderm Derived from yolk sac cells, and therefore from the hypoblast. 12th day Extraembryonic mesoderm is organized in 2 layers: 1) extraembryonic somatic mesoderm (lining the cytotrophoblast) 2) extraembryonic splanchnic mesoderm (lining the yolk sac). BILAMINAR GERM DISC 4. Second week of development Primary villi Langmann´s medical embryology. 13 Ed. th 13th-14th day • Primary villi: Cytotrophoblast surrounded by syncytiotrophoblast. • Secondary yolk sac (will constitute part of the digestive tube). • Primitive uteroplacental circulation begins. • Connecting stalk is formed (will give rise to umbilical ABNORMAL IMPLANTATION 4. Second week of development Langmann´s medical embryology. 13th Ed. GASTRULATION 5. Third week of development • The most characteristic event occurring during the third week of gestation is gastrulation. • It is the process that establishes the 3 germ layers: endoderm, mesoderm and ectoderm. • It begins with the formation of the primitive streak (narrow groove on the surface of the epiblast). • Epiblast cells migrate and differentiate to form endoderm and mesoderm. • Non-migrating cells differentiate and form ectoderm. Langmann´s medical embryology. 13th Ed. GASTRULATION 5. Third week of development Primitive pit B They become intercalated in the hypoblast. • • Prenotochordal cells invaginating the primitive node move forward cranially in the midline. Langmann´s medical embryology. 13th Ed. C • • Day 17 Proliferate and detach from the hypoblast. NEURULATION 6. Fourth week of development 1. Ectoderm gets thicker and form the neural plate. 2. Neural plate (neuroectoderm) gradually folds and fuse to form the neural tube. A 3. Cells in the neural crest differentiate in melanocytes, hair follicles, sensory ganglia, sympathetic neurons, glial cells, adrenal medulla, craniofacial skeleton and cranial ganglia. B C D Images adapted from: Langmann´s medical embryology. 13th Ed. DERIVATIVES 6. Fourth week of development ECTODERM Gastrointestinal tract, respiratory tract, and urinary bladder. Parenchyma of the thyroid, parathyroids, liver, and pancreas. And the epithelial lining of the tympanic cavity and auditory tube. ENDODERM Central nervous system, peripheral nervous system, sensory epithelium of ear, nose, and eye, skin, including hair and nails, pituitary, mammary, and sweat glands, and enamel of the teeth. Muscles, cartilages, bones, dermis of skin, cardiovascular apparatus (heart, arteries, veins, lymph vessels, and all blood and lymph cells, urogenital apparatus (with exception of the bladder), suprarenal glands. MESODERM External appearance - 4th week 6. Fourth week of development The main external features are the somites and pharyngeal arches. Langmann´s medical embryology. 13th Ed. External appearance - 2nd month By the end of the embryonic period: •the main organ systems have been established. •The major features of the external body are recognisable. Langmann´s medical embryology. 13th Ed. From 9th week to birth - Foetal period Characterised by maturation of tissues and organs growth of the body. Langmann´s medical embryology. 13th Ed. and rapid BIBLIOGRAP HY Drake RL, Vogl AW, Mitchell AWM. Gray's Basic Anatomy, 4th Edition. Philadelphia, PA: Elsevier, 2019. Sadler TW. Langman´s Medical Embryology. 13th Ed. Walters Kluwer, 2015. Sadler TW. Langman´s Medical Embryology. 14th Ed. Walters Kluwer, 2019. Schoenwolf GC, Bleyl SB, Brauer PR, Francis-West PH. Larsen's Human Embryology. 6th Ed. Elsevier, 2021. Maria del Mar Ubero Martinez [email protected] UCAM Universidad Católica de Murcia © UCAM