Introduction to Human Embryology (L6) PDF

 Trimester - period of pregnancy consists of 3 calendar months. - 9 months are divided into 3 trimesters.  Abortion: expulsion of embryo or fetus before being viable. ‫ قبل ان يصبح قابل للعيش‬L‫ طرد الجن‬-...

 Trimester - period of pregnancy consists of 3 calendar months. - 9 months are divided into 3 trimesters.  Abortion: expulsion of embryo or fetus before being viable. ‫ قبل ان يصبح قابل للعيش‬L‫ طرد الجن‬- ‫ ناصج بما فيه الكفاية للبقاء على قيد الحياة خارج الرحم‬-  Viable: mature enough to survive outside the uterus.  Human embryonic stem cells are pluripotent : able to di erentiate into di erent cell type  Directional terminology and body planes Anatomical position: >>> Anterior /Posterior >>> Superior /Inferior IN ANATOMY >>> Lateral /Medial >>> Caudal /Cranial IN EMBERUO superior inferior >>> Dorsal /Ventral interior superior >>> Sagittal plane >>> Coronal section >>> frontal plane >>> Transverse section  TYPES OF CELLS ‫تساوي‬C‫نقسام ا‬F‫ا‬ - Somatic cells: have 2 sets of chromosomes= diploid number= 2n= 46 Divide by mitosis. ‫نصف‬C‫نقسام ا‬F‫ا‬ - Germ line cells: have 2 sets of chromosomes= diploid number= 2n= 46 Divide by meiosis giving gametes are produced from germ cells have 1 set of chromosomes= haploid number= 1n= 23 chromosomes. - In embryos Gametes are derived from primordial germ cells that are formed in the epiblast later they migrate to the wall of the yolk sac then migrate from the yolk sac toward the developing gonads ( reach by week 5) then through Mitosis to increase in their ‫ولية‬%‫يا الجرثومية ا‬.‫مشاج من الخ‬%‫ يتم اشتقاق ا‬،‫جنة‬%‫في ا‬ numbe then gametogenesis produces gametes. ‫يا إلى‬.‫ح ًقا تهاجر هذه الخ‬F.‫ست‬.‫يبي ب‬K‫التي تتكون في ا‬ ‫ح باتجاه الغدد التناسلية‬S‫ ثم تهاجر من كيس ا‬،‫ح‬S‫جدار كيس ا‬ - Traits are determined by specific genes on chromosomes. ‫نقسام‬F‫ل ا‬.‫ ثم من خ‬،(‫سبوع الخامس‬%‫النامية )تصل بحلول ا‬ - Humans have 23,000 genes on 46 chromosomes. ‫مشاج‬%‫ ومن ثم تقوم عملية تكوّن ا‬،‫يتوزي تزداد في عددها‬S‫ا‬.‫مشاج‬%‫بإنتاج ا‬ - In somatic cells, chromosomes appear as 23 homologous pairs to form the diploid number of 46. - There are 22 pairs of matching chromosomes, the autosomes, and one pair of sex chromosomes. -If the sex pair is XX, the individual is genetically female; if the pair is XY, the individual ‫مومية‬R‫مشاج ا‬R‫يُشتق كروموسوم واحد من كل زوج من ا‬ is genetically male..(‫نوي‬C‫بوية )الحيوان ا‬R‫مشاج ا‬R‫ وا]خر من ا‬،(‫)البويضة‬ - One chromosome of each pair is derived from the maternal gamete, the oocyte, and one from the paternal gamete, the sperm. - Each gamete contains a haploid number of 23 chromosomes, and the union of the gametes at fertilization restores the diploid number of ‫نطقة التي يتم فيها ربط الكروماتيدات الشقيقة م ًعا بعد تكرار الكروموسوم‬C‫ هو ا‬:‫السنترومير‬  Centromere vs. Kinetochore - Centromere : the region where the two sister chromatids are held together after the replication of chromosome. - Kinetochore: the protein complex on the chromosome where spindle fibers are attached during cell division.  Cell division - There are 2 type of cell division 1. Mitosis ‫اﻻﻧﻘﺳﺎم اﻟﻣﺗﺳﺎوي‬ 2. Meiosis ‫اﻻﻧﻘﺳﺎم اﻟﻣﻧﺻف‬ 1. Mitosis.‫م‬R‫ مع الخلية ا‬L‫ متطابقت‬L‫ ابنت‬L‫هي عملية انقسام الخلية كالتي تنتهي بخليت‬ - Is the process of cell division ending with two daughter cells that are identical to the parent cell - Before a cell enters mitosis, each chromosome replicates its DNA (chromosomes are extremely long, they are spread di usely through the nucleus, and they cannot be recognized with the light microscope). - Stage of mitosis o Prophase  Prometaphase  Metaphase  Anaphase  Telophase  Daughter cells -chromosomes begin to coil, - The chromosomes - mitotic spindles -migration of contract, and condense. line up in the are formed. the chromatids to equatorial plane, centromere of opposite poles of -Each chromosome consists doubled structure is each the spindle. of two parallel chromatids, visible. chromosome Cytokinesis: joined at a narrow divides. cytoplasm region(centromere). division - chromosomes continue to condense, shorten, and thicken..‫نكماش‬s‫ وا‬،‫لتفاف‬s‫ ا‬،‫~ تبدأ الكروموسومات بالتكثف‬ ‫~ تصطف الكروموسومات في مستوى‬.‫نقسامية‬s‫غازل ا‬C‫~ تتكون ا‬ ‫غزل‬C‫~ تتحرك الكروماتيدات إلى قطبي ا‬ ‫ بمنطقة ضيقة تُسمى‬L‫~ يتكون كل كروموسوم من كروماتيدين متصل‬.‫استوائي وسط الخلية‬ ‫ وينقسم كل‬،‫~ تنفصل السنترووميرات‬.‫زم‬r‫زمي لتقسيم السيتوب‬r‫نقسام السيتوب‬s‫~ يحدث ا‬.‫السنتروومير‬.‫زدوج للكروموسوم مرئيًا‬C‫~ يصبح التركيب ا‬.‫كروموسوم‬.‫ وزيادة السماكة‬،‫ التقصير‬،‫~ تستمر الكروموسومات في التكثف‬  2. Meiosis.‫مشاج‬R‫نتاج ا‬F ‫يا الجرثومية‬r‫يا الذي يحدث في الخ‬r‫هو انقسام الخ‬ - is the cell division that takes place in the germ cells to produce gametes - They are 2 type: meiosis I & meiosis II - To reduce the number of chromosomes to the haploid number of 23 - Stage of meiosis : a) Cells replicate their DNA at the beginning of meiosis I (each of the 46 chromosomes is duplicated into sister chromatids). b) Synapsis:Homologous chromosomes then aline a themselves in pairs The pairing is exact and point for point except for the XY combination. c) Seperation:Homologous pairs then separate into two daughter cells, thereby reducing the chromosome number from diploid to haploid. As separation occurs, points of interchange are temporarily united and form an X-like structure, a chiasma. d) Crossover: are the interchange of chromatid segments between paired homologous chromosomes..‫ا&قترنة‬ ‫ الكروموسومات ا&تماثلة‬3‫العبور هو تبادل أجزاء من الكروماتيدات ب‬ Summary of meiosis: A) Homologous chromosomes approach each other..‫ وكل منها يتكون من كروماتيدين‬،‫تماثلة تتزاوج‬C‫الكروموسومات ا‬ B) Homologous chromosomes pair, each consists of two chromatids..(‫زدوجة تتبادل أجزاء من الكروماتيدات )عبور جيني‬C‫تماثلة ا‬C‫الكروموسومات ا‬ C) Paired homologous chromosomes interchange chromatid segments [crossover]..‫زدوجة تنفصل عن بعضها‬C‫الكروموسومات ذات البنية ا‬ D) Double - structured chromosomes pull apart. E) Anaphase of the first meiotic division..‫ول‬C‫نقسام ا&يوزي ا‬H‫نفصالي ل‬L‫الطور ا‬.‫زدوجة عند السنترومير‬C‫ تنفصل الكروموسومات ذات البنية ا‬،‫يوزي الثاني‬C‫نقسام ا‬s‫ل ا‬r‫خ‬ F,G) During the second meiotic division, the double— structured chromosomes split at the centromere. - At completion of division, chromosomes in each of the four daughter cells are di erent from each - Results of meiotic divisions: a) Genetic variability (Crossover redistributes genetic material ). b) Random distribution of homologous chromosomes to the daughter cells. c) Each germ cell contains a haploid number of chromosomes so that at fertilization, the diploid number of 46 is restored. Spermatogenesis in males starts at puberty (13-16y)  Gametogenesis in females starts during fetal period stop Oogenesis during meiosis 1, resume at puberty o Spermatogenesis - Transformation of spermatogonia into spermatozoa..‫نوية‬C‫نوية البدائية إلى الحيوانات ا‬C‫يا ا‬r‫~ تحول الخ‬ - Spermatogenesis process requires 2 months (64 days). - Takes place at puberty within seminiferous tubules of testes..L‫نوية في الخصيت‬C‫نابيب ا‬R‫~ تحدث عند البلوغ داخل ا‬ I. Spermatocytogenesis: division & growth of primitive sperm cells (spermatogonia) into spermatocytes II. Meiosis: division of spermatocytes (2n) into haploid cells (spermatids, 1n) III. Spermiogenesis: transformation (Metamorphosis) of spermatids into sperms (spermatozoa)   Spermatogonia (primitive germ cells):.‫ بعد البلوغ تنقسم انقسا ًما ميتوزيًا‬.‫ل الفترة الجنينية‬r‫~ موجودة خ‬  Present during fetal period After puberty mitosis.‫ولية‬R‫نوية ا‬C‫يا ا‬r‫~ تزداد في الحجم لت ُك ّون الخ‬  increase in size to form Primary spermatocytes  Primary spermatocytes:  Largest germ cell in seminiferous tubules (2n). ‫نوية‬C‫نابيب ا‬R‫أكبر خلية منوية في ا‬  Enter the first meiotic division to form Secondary spermatocytes.‫نوية الثانوية‬C‫يا ا‬r‫ول لت ُك ّون الخ‬R‫يوزي ا‬C‫نقسام ا‬s‫تدخل ا‬  Secondary spermatocytes:  chromosomes (1n)  Enter the 2nd meiotic division to produce spermatids.‫نوية‬C‫نتاج الحيوانات ا‬F ‫يوزي الثاني‬C‫نقسام ا‬s‫~ تدخل ا‬  Spermatids:  (1n).(‫نوية‬C‫نوية غير الناضجة إلى حيوانات منوية ناضجة )الحيوانات ا‬C‫التحول من الحيوانات ا‬  Spermiogenesis :The transformation of spermatids into elongated sperms (spermatozoa) Mature Sperm consist of : > Head: nucleus & acrosome > Neck > Tail: middle piece there are mitochondria, Principal piece end piece o Oogenesis - Is the formation of gametes in the ovaries occurs (2n) ‫جموعة الكروموسومية‬C‫يا بويضية ثنائية ا‬r‫ولية ستتطور لتصبح خ‬R‫يا الجرثومية ا‬r‫الخ‬ 1. Primordial germ cells will develop to give diploid (2n) oogonia. ‫يا البويضية الثنائية‬H‫تنقسم الخ‬2. Diploid oogonia divide by mitosis during early fetal development to produce ‫ل تطور‬H‫انقسا ًما ً ميتوز ًيا خ‬ millions of germ cells; before birth, most of the latter degenerate by atresia. 3‫ي‬H‫ ا&بكر لتنتج م‬3‫الجن‬ 3. Few oogonia will develop into larger cells, called primary oocytes. ،‫دة‬L‫يا الجرثومية؛ قبل الو‬H‫الخ‬ ‫يا تتحلل بسبب‬H‫معظم هذه الخ‬4. primary oocytes enter prophase of meiosis I during fetal development.‫عملية تسمى الرتق‬ but do not complete this phase until after puberty. 5. Each month during a woman’s reproductive years, several primordial ‫ل سنوات‬r‫كل شهر خ‬ follicles ( primary oocyte and single layer of follicular cells) start to grow ‫ تبدأ‬،‫التكاثر للمرأة‬ ‫العديد من البويضات‬ and become primary follicles( surrounded by several layers of follicular cells).‫ولية في النمو‬R‫ا‬ 6. Follicle grows and cells around oocyte secrete a fluid in a cavity ( antrum), follicle is now secondary follicle 7. After puberty, each month meiosis I resume in several secondary follicles, only one will mature fully to give two haploid cells ( secondary oocyte and 1st polar body) 8. Secondary oocyte and 1st polar body begin meiosis II and stop atmetaphase ii 9. Ovulation occurs.‫ البويضة والجسم القطبي الثاني‬:L‫ وتنقسم الخلية الثانوية إلى خليت‬،‫يوزي الثاني‬C‫نقسام ا‬s‫ سيستأنف ا‬،‫خصاب‬F‫إذا حدث ا‬ 10. If fertilization occurs, meiosis II will resume and the secondary oocyte divides into two haploid cells: the ovum and a 2nd polar body 11. The sperm will unite with the ovum to give thezygote.(‫قحة‬r‫نوي سيتحد مع البويضة لتكوين الزيجوت )ال‬C‫الحيوان ا‬ Characteristics of Oogenesis: ‫جردة‬C‫ ا‬L‫الع‬ - Secondary oocyte is a large cell can be seen by naked eye - Secondary oocyte at ovulation begins 2nd miotic division and stop at metaphase - If fertilization occurs it will resume meiosis II - If no fertilization it will degenerate - A new born ovary contains up to 1 million primary oocyte - At puberty only 40000 - remain 400 mature secondary oocytes ovulated during life of females.(‫شع‬C‫كليل ا‬F‫يا الجريبية )ا‬r‫نطقة الشفافة وطبقة من الخ‬C‫ تُحاط الخلية البيضية الثانوية بطبقة مادية تُعرف باسم ا‬،‫أثناء تطور الحويصلة‬ - Zona pellucida :During follicle development the secondary oocyte is surrounded by a covering of a material. - Corona radiata : a layer of follicular cells. - Cumulus oophorus : follicular cells project into antrum ‫يا الجريبية تُبرز داخل التجويف‬r‫~ الخ‬  MALE VS FEMALE GAMETOGENESIS MALE FEMALE Highly motile ‫شديدة الحركة‬ Not motile ‫غير متحركة‬ Small sized ‫صغيرة الحجم‬ Large sized ‫كبيرة الحجم‬ Two types: x- chromosomes’ sperms and y- chromosomes’ One type with Xchromosome ‫ فقط‬X ‫نوع واحد يحتوي على الكروموسوم‬ spermsY ‫ وأخرى تحتوي على الكروموسوم‬X ‫ حيوانات منوية تحتوي على الكروموسوم‬:‫نوعان‬ 4 sperms result from division.‫يا‬r‫نوية تنتج نتيجة انقسام الخ‬C‫الحيوانات ا‬ 1 oocyte result from cell division.‫يا‬r‫بويضة واحدة تنتج من انقسام الخ‬  Transport MALE FEMALE - Sperms will move from epididymis by peristaltic movement. - An oocyte will enter the first part of Fallopian tube as - Secretions from the gland will be added to form semen fimbriae will move making a current , then to ampulla and then semen ejaculated. and isthmus through peristaltic movement of the tube - NUMBER of sperms is 200-600 million. and finally enter the uterus - sperms are highly motile and they will travel in the vagina. - vaginal plug will be formed by semen to prevent backflow of it out. - 200 sperms reach fertilization site..‫نوية الطازجة غير قادرة على تخصيب البويضة‬C‫الحيوانات ا‬1..‫ ساعات‬7 ‫هناك فترة تكيّف تستمر حوالي‬.2  Maturation of sperms capacitation ‫ء الجليكوبروتيني والبروتينات الحويصلية من سطح‬r‫يتم إزالة الط‬.3 - Fresh sperms are unable to fertilize an ovum..‫كروسوم‬R‫ا‬ - There is about 7 hours conditioning period..‫ توجد تغييرات شكلية ولكن يزداد النشاط في الرحم أو قناتي فالوب‬s.4 - Glycoprotein coat and seminal proteins removed from surface of acrosome. - No morphological changes but increased activity Occurs in uterus or uterine tubes.  Fertilization - Oocytes should be fertilized within 12 hours They can not do so after 24 hours as they will degenerate. - Invetro fertilization (outside the body) can occur even if gametes were frozen for many years. - Fertilization: Fusion of male gamete & female gamete to form the zygote. - begins with the contact between the oocyte and the sperm, and ends with intermingling of maternal & paternal chromosomes at metaphase of the 1 st mitotic division of the zygote. - Locations : ampulla of uterine tube. ‫أمبولة قناة فالوب‬  ‫شع‬C‫كليل ا‬s‫نوي عبر ا‬C‫مرور الحيوان ا‬.1 Phases of fertilization ‫نوي‬C‫كروسوم الخاص بالحيوان ا‬s‫الهيالورونيداز من ا‬- 1-Passage of sperm through corona radiata. - Hyaluronidase from acrosome of the sperm 2-Penetraton of the zona pelleucida. - Acrosomal enzymes (Acrosin, esterases, & neuraminidase)  lysis of zona pellucida  path for the sperm 3- Fusion of plasma cell membaranes of the oocyte and the sperm. - Zona reaction: changes in the properties of Z.P. that makes it impermeable to other sperms 4- Completion of the second meiotic division of the oocyte. - Completion of the second meiotic division of the oocyte & forms 5- Formation of the male pronulceus. - Sperm nucleus enlarge & become rounded Tail degenerates 6-Break down of pronuclear membaranes. 7. Breakdown of the pronuclear membranes - Condensation of the chromosomes, mitotic cell division first cleavage division of the zygote occurs. Results of fertilization 1- stimulates the secondary oocyte to complete the 2nd meiotic division producing the second polar body. 2- restores the normal diploid number (46) in the zygote. 3- results in variation of human sepcies..‫ مما ينتج الجسم القطبي الثاني‬،‫يوزي الثاني‬C‫نقسام ا‬s‫كمال ا‬F ‫يحفز البويضة الثانوية‬.1 4- determines the chromosomal sex of the embryo..‫( في الزيجوت‬46) ‫يعيد العدد الثنائي الطبيعي للكروموسومات‬.2.‫نواع البشرية‬R‫يؤدي إلى تنوع ا‬.3 5- causes metabolic activation of the oocyte , which initiates cleavage of the zygote..L‫يحدد الجنس الكروموسومي للجن‬.4.‫ مما يبدأ عملية انقسام الزيجوت‬،‫يضي للبويضة‬R‫يسبب التنشيط ا‬.5 Cleavage of The Zygote - Repeated mitotic divisions of the zygote into many cells (Blastomeres) - Compaction: compact ball of tightly aligned cells after 8 cell stage - Morula (like mulberry): 12 to 32 blastomeres surrounded by zona pellucida - 4 days after fertilization * time to enter the uterine cavity.(Blastomeres) ‫يا عديدة‬r‫انقسامات ميتوزية متكررة للزيجوت إلى خ‬.1.‫يا‬r‫ خ‬8 ‫تراصة بإحكام في مرحلة‬C‫يا ا‬r‫ تشكيل كرة مدمجة من الخ‬:Compaction.2.‫نطقة الشفافة‬C‫ستوميرية محاطة با‬r‫ خلية ب‬32 ‫ إلى‬12 :(‫ )مثل التوت‬Morula.3.‫زم للدخول إلى تجويف الرحم‬r‫خصاب = الوقت ال‬F‫ أيام من ا‬4 ‫بعد‬.4 Blastogenesis - Early blastocyst: (late Day 4) Fluid-filled space is formed Fluid comes from uterine fluid. - Late blastocyst: (Day 5) Z.P. is shed at day 5 hatching blastomeres di erentiate into: 1. Trophoblast: outer cell layer = embryonic part of placenta. 2. Inner cell mass (embryoblasts): a group of blastomeres gathered at periphery give rise to the embryo. Cleavage Occurs in the uterine tube Once the zygote has reached two cell stage it undergoes a series of mitotic divisions, increasing the number of cells. These cells which become smaller with each cleavage division, are known as blastomeres. Division of the zygote begins approximately 30 hrs. After fertilization. During cleavage the zygote is still surrounded by zona pellucida. Until the eight cell stage , they form a loosely arranged clump. After the 3rd cleavege blastomeres form a compact ball of cells ‫ تنقسم‬،‫خصاب‬F‫ أيام من ا‬3 ‫بعد حوالي‬ Morula ‫ضغوط مرة أخرى لتكوين‬C‫ ا‬L‫يا الجن‬r‫خ‬ (‫ خلية )تشبه التوت‬16 ‫كونة من‬C‫التوتية ا‬ Approximately 3 days after fertilization, cells of the compacted embryo divide again to form a 16-cell morula (mulberry). 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 to the placenta. ‫ح ًقا‬s ‫ التي تساهم‬،‫غذية‬C‫رومة ا‬R‫ بينما تشكل الكتلة الخلوية الخارجية ا‬،‫ الفعلي‬L‫تشكل الكتلة الخلوية الداخلية أنسجة الجن‬ ‫شيمة‬C‫في تكوين ا‬ Blastocyst Once the morula enters the uterine cavity, fluid will penetrate through the zona pellucida into the intercellular spaces of the inner cell mass. Gradually, the intercellular spaces become confluent, and finally, one cavity (blastocele), forms and the embryo is a blastocyst.  :L‫ستومير إلى قسم‬r‫يا الب‬r‫تنقسم خ‬ ‫قطاب‬R‫يا الكتلة الخلوية الداخلية تكون في أحد ا‬r‫ خ‬:‫رومة الجنينية‬R‫ ا‬.‫أ‬ Blastomeres separated into two parts:- ‫ريمية‬R‫ الكتلة الخلوية الخارجية تصبح مسطحة وتشكل الجدار الظهاري للكيسة ا‬:‫غذية‬C‫رومة ا‬R‫ ا‬.‫ب‬ A. embryoblast: Cells of the inner cell mass are at one pole ‫نغراس‬s‫ مما يسمح ببدء ا‬،‫نطقة الشفافة‬C‫~ اختفت ا‬ (‫نغراس‬s‫غذية ستخترق بطانة الرحم حوالي اليوم السادس )ا‬C‫رومة ا‬R‫~ ا‬ B. trophoblasts: the outer cell mass flatten and form the epithelial wall of the blastocyst. The zona pellucida has disappeared, allowing implantation to begin. trophoblastic will penetrate endometrium the uterus on about the sixth day (implantation) Implantation - The entrance of the blastocyst into the thick endometrium of the uterus - Time: Starts at 6th-8th day and completed at 12th day 1. Blastocyst attaches to endometrial epithelium 2. Trophoblast proliferate & di erentiate into two layers: a) Cytotrophoblasts inner layer of cells b) Syncytiotrophoblast layer: outer layer of multinucleated protoplasmic mass of tissue (no cell boundaries) Erode the.‫نوية )بدون حدود خلوية( تعمل على تآكل بطانة الرحم‬R‫زمية متعددة ا‬r‫ الطبقة الخارجية من كتلة سيتوب‬:‫خلوية‬C‫رومة الغاذية ا‬R‫طبقة ا‬ endometrium 3. The blastocyst becomes embedded into the endometrium The site of implantation is closed by a fibrin clot. 4. the blastocyst is completely embedded in the endometrium & the surface epithelium covers the original defect in the uterine wall Syncytiotrophoblast Multinucleated protoplasmic mass Have a phagocytic function... ALSHAWABKEH