Embryology Study Questions PDF

Gametogenesis 1.​ Describe the origin and fate of the primordial germ cells. a.​ Primordial germ cells are cells that give rise to gametes, they arise from epiblasts and move through the primordial streak during gastrulation and migrate to the yolk sac walls...

Gametogenesis 1.​ Describe the origin and fate of the primordial germ cells. a.​ Primordial germ cells are cells that give rise to gametes, they arise from epiblasts and move through the primordial streak during gastrulation and migrate to the yolk sac walls. At 4 weeks the primordial germ cells in the yolk sac walls migrate to the posterior body wall to the area of the developing gonads. 2.​ Compare and contrast spermatogenesis and oogenesis, including stages of gametogenesis for each. a.​ Both male and female germ cells start as diploid cells and undergo mitosis and meiosis. Female germ cell mitosis occurs between 3-5 months of life in utero (this limits the number of oocytes females will produce in their lifetime). Male germ cell mitosis occurs after puberty and continues throughout their lifetime. Meiosis in males creates 4 identical mature spermatids. Meiosis in females produces one mature oocyte and 3 non functional polar bodies. Meiosis 2 in males is completed before the mature sperm is released. Meiosis 2 in females is not completed until the ovulated oocyte is fertilized by sperm. Fertilization and Implantation 1.​ What is the role of the fimbriae in the process of fertilization? a.​ It moves the oocyte into the uterine tube 2.​ Describe the main parts of a sperm cell. a.​ The head covered by acrosome, neck and tail 3.​ What is the function of the acrosome? a.​ Covers the head of the sperm 4.​ What is the zona pellucida? a.​ A glycoprotein shell that surrounds the ovulated oocyte. 5.​ What changes must sperm undergo before they can fertilize an oocyte? a.​ Capacitation: the glycoprotein coat and the seminal proteins are removed from the sperm's acrosome. 6.​ Where does fertilization take place? a.​ Ampulla of uterine tube 7.​ Define the function of the corpus luteum as it relates to hormonal changes in the endometrium, following ovulation. a.​ After the egg is released through stimulation of luteinizing hormone (LH) the corpus luteum (a mass of cells) forms in the empty follicle. The corpus luteum secretes progesterone, which causes the endometrium to thicken further. 8.​ Describe the sequence of events involved in fertilization. a.​ Capacitated sperm passes through corona radiata, acrosome reaction: the release of acrosomal enzymes allows sperm to penetrate the zona pellucida, sperm penetrates the zona pellucida, zona reaction: sperm penetration causes cortical granules to release making the zona pellucida impenetrable, sperm and oocyte membranes fuse, resumption of oocyte meiosis metaphase 2. Final product is a zygote. 9.​ Describe the processes of cleavage, compaction, and blastocyst formation. a.​ Cleavage is a series of rapid mitotic divisions, a 2 cell zygote becomes a 4 cell zygote, the zygote is growing in cell number not size, these new cells are called blastomeres. Compaction happens when blastomeres start to adhere tightly to one another through junctional complexes and cell surface adhesion  glycoproteins, precursor to a blastocyst. At 32 cells the embryo is now a morula. Blastocyst formation is when the morula develops a fluid filled cavity. Early blastocysts still have a zona pellucida. 10.​Describe the late (hatched) blastocysts, including distinct parts and derivatives. a.​ A late stage blastocyst sheds its zona pellucida prior to implantation. It will have an embryoblast (an inner cell mass) a blastocystic cavity, and trophoblast (outer cell mass). The embryoblast will become the embryo proper and the trophoblast will become the placenta. 11.​Describe the process of implantation, including sequence of events and structural changes/development (“rule of twos”). a.​ The embryoblast splits into two germ layers: the epiblast and the hypoblast. The trophoblast will give rise to two tissue types the cytotrophoblast and the syncytiotrophoblast. The blastocyst cavity is remodeled twice into the primary yolk sac and then into the definitive yolk sac. Two new cavities appear: the amniotic cavity and the chorionic cavity. And the extra embryonic mesoderm splits into two layers. The late stage blastocyst contacts the uterine endometrium at the embryonic pole and begins to implant. 12.​What are the two layers of the bilaminar disc? a.​ Epiblast and hypoblast 13.​What are trophoblastic lacunae, and where do they form? a.​ They are pools of maternal blood and they form in the syncytiotrophoblast. 14.​What is the significance of the coagulation plug at the implantation site? a.​ It's a temporary seal that prevents excess bleeding of the uterine lining after implantation. 15.​Explain the significance of the amniotic cavity expanding. 16.​It creates a protective fluid filled space that surrounds the embryo, cushioning it, regulating temperature and giving it space to move around. 17.​What is an ectopic pregnancy? a.​ When implantation occurs in an abnormal site not the ampulla of the uterine tube. Can be life threatening and need surgery. Can be detected when pregnancy hormones such as HCG are detected in increasing levels but no embryo is seen in the uterine cavity. Gastrulation and Neurulation 1.​ Describe the process of gastrulation and identify associated structures and derivatives, including three germ layers, primitive streak, and notochord. a.​ Gastrulation occurs when the primitive streak appears, epiblast cells travel through the primitive streak and become the mesoderm. There are now three germ cell layers; ectoderm, mesoderm, and endoderm. The notochordal process comes from mesoderm that migrates cranially in the midline and will become the notochord. 2.​ Describe the tissues and organs formed from the three germ layers- ectoderm, mesoderm and endoderm. a.​ Ectoderm becomes the skin, hair, nails, sweat glands, brain and spinal cord. Mesoderm becomes the paraxial mesoderm (axial skeleton, voluntary muscles, and pats of the dermis), intermediate mesoderm (urinary system and part of the genital system), lateral plate mesoderm( parts of limb and dermis). Endoderm becomes the lining of the gut.  3.​ Describe the process and time course of neurulation and identify associated structures and derivatives, including neural plate, neural tube, neural crest, neuropores, and nervous system structures. a.​ Neurulation is the process by which the neural tube and neural groove closes, the neural plate is also formed. This occurs weeks 3 and 4. Neural crest cells and neural tubes dissociate from the surface of the ectoderm and each other. Fusion begins in the cervical region and proceeds cranially towards the neuropores. The cranial neuropore closes around Day 24 and caudal neuropore closes on day 26. Neurulation is complete when the neuropores are closed. 4.​ List the cell type/tissue derivatives of the neural crest cells. a.​ Cranial neural crest cells can become: cranial nerve ganglia, odontoblasts, connective tissue surrounding the eye, pharyngeal arch cartilages, dermis of face and neck, schwann cells of PNS, melanocytes, arachnoid and pia mater. Trunk (spinal) neural crest cells can become: preaortic ganglia, adrenal medulla, dorsal root ganglia, sympathetic chain ganglia, schwann cells of PNS, melanocytes, arachnoid and pia mater. 5.​ What are somites and what do they become? a.​ As neurulation occurs the differentiation of paraxial mesoderm into a series of rounded structures called somitomeres. Theses structures are paired up in the cranio-caudal progression starting in the cranial region. The remaining somitomeres condense into somites. Somites establish the segmental organization of the body by creating most of the axial skeleton, neck muscles, body wall, and limbs. 6.​ What are the two components of somites and what do they become? a.​ The two components of dermomyotome and sclerotome. Dermomyotome contributes to the dermis of the skin, forming the myotome; the dorsal and ventrolateral muscles of the body wall and limb muscles. Sclerotome develops into the vertebrae, the ventral portion surrounds the notochord and will form the vertebral arch, the dorsal portion flanks the neural tube and will form the vertebral arch. 7.​ Describe common malformations arising as a result of disruption of gastrulation and neural tube closure. a.​ Sacrococcygeal teratoma is a malformation that is the result of the primitive streak not regressing. A cluster of pluripotent cells proliferate to form a teratoma. The tumors usually have tissues from all three germ layers (ectoderm, mesoderm, and endoderm). b.​ Anencephaly, Spina bifida, and Encephalocele are neural tube defects that occur when a part of the neural tube does not close, the CNS, vertebral arches, and skull formation can be affected. Development of Body Cavity 1.​ Explain the formation of the intraembryonic coelom and the role of embryonic folding in this process. a.​ The lateral plate mesoderm will divide into two layers the somatic mesoderm and  the splanchnic, the space bordered by these two layers is the start of the intraembryonic coelom. This space is open before lateral folding occurs. When the folds of the embryo fuse along the ventral midline, this space enclosed within the embryo becomes the intraembryonic coelom. 2.​ Define pericardioperitoneal canal, pleuropericardial fold and membrane, pleuroperitoneal fold and membrane, dorsal mesentery, ventral mesentery, mesentery of esophagus. a.​ Pericardioperitoneal canal: Openings from the abdomen to the thorax posterior to the septum transversum that are closed by the pleuroperitoneal membranes during formation of the diaphragm b.​ Pleuropericardial fold and membrane: Extensions of mesoderm that extend from the lateral body wall that meet in the midline to separate the pleural and pericardial cavities. The folds carry the phrenic nerve and contribute to the parietal pericardium and form the fibrous pericardium. c.​ Pleuroperitoneal fold and membrane: Extension of mesoderm that extend from the body wall to meet with septum transverum and mesentery of the esophagus, closing the pericardioperitoneal canals during the formation of the diaphragm. d.​ Dorsal mesentery: A double layer of peritoneum suspending the gut tube from the dorsal body wall from the lower end of the esophagus to the rectum. The gut will grow and rotate and some parts are lost as portions of the gut fuse to the posterior body wall (parts of the duodenum and colon) e.​ Ventral mesentery: A double layer of peritoneum derived from the septum transversum and extending from the liver to the ventral body wall and form the liver to the stomach and duodenum. f.​ Mesentery of esophagus: A double layer of peritoneum suspending the esophagus that develops into the cura of the diaphragm around the aorta. 3.​ Explain the origin of the septum transversum and how it assumes its definitive position. a.​ The septum transversum is a wedge-like piece of mesoderm that forms a ventral structure partially dividing coelom into a thoracic primitive pericardial cavity and an abdominal peritoneal cavity. Cranial body folding and differential growth move the septum transversum from the cranial edge of the embryonic disc caudally to the position of the future diaphragm. 4.​ Correlate the 3 principal body cavities of the adult with various regions of the embryonic coelomic cavity. a.​ Pericardial Cavity: Develops from the most interior portion of the intraembryonic coelom. i.​ Adult Function: Encloses the heart b.​ Pleural Cavities: Develops from lateral portions of the intraembryonic coelom. i.​ Adult Function: Each encloses a lung c.​ Peritoneal Cavity: Develops from the posterior portion of the intraembryonic coelom. i.​ Adult Function: Encloses most of the abdominal organs. 5.​ Explain the partitioning of intraembryonic coelom and the roles of the pleuropericardial and pleuroperitoneal folds/membranes. a.​ In order to properly partition the intraembryonic coelom structures need to come  together to separate the thoracic and abdominal cavities. The thorax will be separated into three cavities. b.​ Pleuropericardial Folds: Grow ventrally from the lateral body walls. Will fuse to separate the pericardial cavity from the pleural cavities. c.​ Pleuroperitoneal fold/membranes: Grow ventrally from the body walls. Extends to meet the septum transversum, forming the diaphragm. Divides the pleural cavities from the peritoneal cavity. 6.​ Explain the development and associated positional changes of the diaphragm. a.​ Initially the diaphragm lies high in the neck region of the embryo, as the embryo grows it descends to its final position in the diaphragm. Development of Limbs and Lungs 1.​ Summarize the time course of limb development. ○​ At 4-8 weeks Limb bud formation, the Apical ectodermal ridge (AER) appears, limb pattern specification, Sonic hedgehog FGFs appear at the causal end of the upper limb bud, Limb morphogenesis occurs (limb rotation), Apoptosis kills the cells that web the fingers separating them, growth 2.​ Explain how the three axes of limb development form. ○​ Proximal to distal: base to tip (shoulder to digits) ○​ Cranial to caudal: thumb to pinkie ○​ Dorsal to ventral: palm to dorsum (back of the hand) 3.​ Describe the role of the apical ectodermal ridge in limb development. ○​ Forms a dorsal ventral axis and drives development along the proximal-distal axis. It determines which side of the hand is dorsal (back of hand) and ventral (palm of hand) 4.​ Explain how the mesodermal core goes about specifying which segment of the limb will form. ○​ The limb bud core is made of lateral plate mesoderm, Wnt7a signals the the mesoderm to form dorsal structures, Zone of Polarizing activity (ZPA) located on the posterior side of the limb bud signals to secrete SHH which determines the digits formed on the limb bud. (low concentration of SHH will produce a thumb high concentration will produce a pinky) 5.​ List components of the limb derived from somites and lateral plate mesoderm. ○​ (Somites) Paraxial mesoderm produces skeletal muscles ○​ Lateral Plate mesoderm produces bones, connective tissues, and vessels. 6.​ Describe common terms and definitions of limb malformations. ○​ Meromelia: Absence of part of a limb ○​ Amelia, Ectromelia: Absence of one or more limbs ○​ Phocomelia: Short ill formed upper or lower limbs (flipper like) ○​ Hemimelia: Stunting of distal limb segments ○​ Acrodolichomelia: disproportionately large hands or feet ○​ Ectrodactyly: Absence of any number of fingers or toes ○​ Polydactyly: Presence of extra digits or parts of digits ○​ Syndactyly: Fusion of digits ○​ Adactyly: Absence of all of the digits on a limb 7.​ Explain the general process and stages of lung and respiratory tree development. ○​ Embryonic (22 days to 6 weeks): Respiratory divertculum arises as a ventral outpouching of the foregut endoderm and undergoes three rounds of branching,  producing primordia of the lungs, the lung lobes, and the bronchopulmonary segments. The stem of the diverticulum forms the trachea and larynx. ○​ Psudoladular (6 to 16 weeks): Respiratory tree undergoes 14 rounds of branching, forming the terminal bronchioles. ○​ Canalicular (16 to 24 weeks): Each terminal bronchioles divides in to two or more respiratory bronchioles. Respiratory vasculature developes. Blood vessels come next to the lung eppithelium. The lung eppithelium differentiates into specialized cell types: cilliated, secretory, and neuroendocrine. Alveolar ducts appear. ○​ Terminal Sac/Saccular (24 weeks to birth): Respiratory bronchioles subdivide to produce terminal sacs. Blood-air barrier formed. Type II alveolar cells produce surfactant ○​ Alveolar (34 weeks to childhood): Alveoli mature 8.​ Note major anatomical differences between canalicular and saccular phases (what is present at each stage?) ○​ In the canalicular phase the fetus cannot survive, in the saccular phase the fetus can survive with appropriate neonatal care. In the canalicular phase there are respiratory bronchioles being divided and the alveolar ducts appear, in the saccular phase respiratory bronchioles are being subdivided to produce terminal sacs, the blood air barrier is formed, and surfactanct is produces. 9.​ What is the difference between a tracheosophageal fistula and esophageal atresia? ○​ Fistula: Failure to complete the separation of the forgut into the trachea and esophagus. Fluid can aspirate into lungs ○​ Atresia: Abnormal connection between trachea and esophageal lumens can lead to an esophagus that is closed at the end. No nutrition intake, vomiting. Cardiovascular Development 1.​ How is the primitive heart tube formed? ○​ Angiogenic cell clusters develop lateral to the developing pericaridal cavities, Lateral folding brings the endocardial heart tubes into midline positions where they fuse. Heart tube becomes freely suspended in the pericardial cavity when the dorsal mesocardium breaks down. 2.​ What are the parts of the primitive heart tube and what are the adult derivatives? ○​ Sinus venous - coronary sinus ○​ Endocardial cushions - membranous ventricular septum ○​ Bulbus cordis - ventricles ○​ Septum secundum - atrial septum ○​ Truncus arteriosus - proximal part of aorta 3.​ How are the atrioventricular canals formed? ○​ A small wedge of endocardial tissue is formed forcing blood to pick a side. 4.​ How is the atrial septum formed? ○​ 2 phases one before birth and one after. ○​ Septum primun grows from the roof of the atrium, the opening below is the foramen primum. ○​ As the septum primum grows, the tissue develops perferations. ○​ The septum primum reaches the endocardial cushions, some portions are gone creating the foramen secundum. ○​ Septum secundum starts to grow on the right ○​ Septum secundum elongates to overlap with the septum primum. The path between the two septa is the foramen ovale.  5.​ What is the role of the foramen ovale in fetal blood flow? ○​ The foramen ovale allows blood to flow between the atria before birth. 6.​ How is the aorta and pulmonary trunk formed? ○​ The aroticopulmonary septum forms as a spiral. Partitioning thebulbus cordis and the truncus arteriosus, creating 2 outflow paths the aorta and the pulmonary trunk. Neural crest cells. 7.​ How is the interventricular septum formed? ○​ 2 parts: Muscular and membranous ○​ Muscular septum: outgrowth of the ventricular floor, cells in the walls of the bulbus cordis and primitive ventricle proliferate ○​ Membranous septum: right and left bulbar/contruncal ridges and endocardial cushions. Bulbar/contruncal ridges extend into the ventricular region fuse with the muscular septum and endocardial cushions creating two separate blood flows 8.​ Describe blood flow through the primitive heart tube and how it changes when the heart septa are formed. ○​ There is open communication between the 2 ventricles until the end of the 7th week through the interventricular foramen 9.​ Explain the etiology of major atrial and ventricular septal defects. ○​ Ventricular septal defects can be membranous (common) or muscular (rare) ​ With normal BP the VSD will move left to right ​ O2 rich blood can cause issues in other parts of the body, the heart will work harder to correct this: hypertension ​ Uncorrected will lead to heart failure, small defects may fix themselves ​ Separation of the ventricles does not occur until the membranous interventricular septum is formed, defects in the aorticopulmonary septum formation usually lead to VSD 10.​ Explain how anomalies of the great vessels may occur. ○​ Persistent truncus arteriosus: failure of truncus arteriosus to divide. ○​ Transposition of the great arteries/vessicles: aorticopulmonary septum grows straight instead of spiraling. ○​ Overriding aorta or pulmonary trunk: unequal truncus arteriosus division, one artery will be larger, misplaced aortico pulmonary septum does not align with the intraventricular septum (VSD), larger artery overrides VSD and receives blood from both ventricles. ○​ Tetralogy of Fallot: 4 cardiac defects occurring together. Overriding aorta: VSD, stenosis in the outflow region of the right ventricle, right ventricular hypertrophy (increase in right ventricle BP) 11.​ How are the embryonic vessels formed? ○​ Extraembryonic blood vessels are formed from yolk sac extraembryonic mesoderm cells, these cells form a network of angioblastic cells/blood islands, blood islands become angioblastic cords, the interior cells will die off and the cord will become a tube (lumen) ○​ Embryonic blood vessels are formed from splanchnic mesoderm cells, these cells form a network of blood islands that infiltrate all layers, blood islands become angioblastic cords, when the interior cells die off the cords become blood vessels. 12.​ Describe sources of blood cells. ○​ Blood cells are supplied first by the yolk sac, blood cells can form from the inner core cells of the angioblastic cords. They are then supplied by the liver, spleen, thymus and eventually bone marrow. 13.​ Understand the major changes that transition the embryonic aortic arch system into a  mature arterial system. ○​ Arches 1 and 2 largely regress. Arch 5 is gone. Blood from arch 3 goes to the head, blood from arches 4 and 6 go to the trunk. ○​ 3rd arch remains connected at the distal end to the dorsal aorta, the proximal end forms the common carotid arteries, the distal end forms part of the internal carotids. ○​ 4th arch: left forms the midportion of the aortic arch, right forms the proximal segment of the right subclavian artery ○​ 6th arch: left forms the proximal left pulmonary artery, right forms the proximal right pulmonary artery, distal forms the ductus arteriosus. 14.​ Describe the origin of the ductus arteriosus and its role in the fetal circulation. ○​ The ductus arteriosis comes from the distal portion of the 6th arch. It is useful for arterial compensation. 15.​ Describe the major arterial derivatives of the dorsal aorta. ○​ Intersegmental arteries (vertebral, intercostal, lumbar, lateral sacral), Viteline and umbilical arteries (ventral branches), lateral branches (supply renals, suprarenals, gonadals) 16.​ Describe the cause and effect of major arterial anomalies (PDA, double aortic arch, aortic coarctation) ○​ Patent Ductus Atrteriosus: failure of the DA to close after birth, higher left side pressure after birth shunts blood throguh the patent DA and back to the pulmonary arteries. ○​ Coarctation of the aorta: localized narrowing of the aorta in the DA region, collateral circulation can develop ○​ Double Aortic Arch: abnormal persistence of the right dorsal aorta between the 7th intersegmental artery and the junction with the left dorsal aorta, the trachea and the esophagus are trapped inside a vascular ring. 17.​ Identify the 3 embryonic venous systems and the regions they serve. ○​ Umbilical: oxygenated blood from fetal placenta ○​ Vitelline: drains the yolk sac, then GI tract ○​ Cardinal: 3 pairs carry blood from the embryo proper, anterior and posterior cardinals drain into the common cardinals. 18.​ Describe the transformation of the vitelline and umbilical veins. ○​ Viteline veins form a plexus of vessels around the gut before passing through the septum transversum, contributes to the portal vein system. RVV becomes the portal and superior mesenteric veins, midportion forms the hepatic vein, superior portion forms the inferior vena cava. ○​ Umbilical veins bypass the liver and make connections with the plexus of viteline vein vessels growing in the liver. RUV degenerates. LUV: caudal portion becomes the path from placenta to liver, forms an anastomosis with the ductus venosus. The ductus venosus and LUV degenerate after birth to form the ligamentum venosum and ligamentum teres hepatitis. 19.​ Understand the development and fetal role of the ductus venosus. ○​ Ductus venosus forms an anastomosis with the LUV. It shunts half of the oxygeneated blood from the umbilical vein to the right atrium via the inferior vena cava. 20.​ Describe embryonic veins that contribute to the inferior vena cava. ○​ The superior right viteline vein becomes the terminal part of the inferior vena cava. 21.​ Trace the fetal circulation, starting at the umbilical vein. ○​ Umbilical vein, ductus venosus, inferior vena cava, right atrium, foramen ovale,  left atrium, left ventricle, aorta, systemic circulation, umbilical arteries. 22.​ Describe differences in the fetal and postnatal circulatory pathways. ○​ After birth the ductus arteriosus constricts allowing all blood leaving the right ventricle to travel to the lungs via the pulmonary arteries. The foramen ovale closes leaving a small depression called the fossa ovalis, isolating deoxygenated blood within the heart. The inferior vena cava now only carries deoxygenated blood back to the heart. The ductus venosus degenerates and becomes the ligagmentum venosum Reproductive and Urinary System 1.​ Describe the relationship between the development of the urinary and reproductive (genital) systems. a.​ Both systems arise from the intermediate mesoderm, the urogenital ridge gives rise to the nephrogenic cord (becomes the kidneys and ureters) and the gonadal ridge (becomes the testes or ovaries) 2.​ Describe the development of the testes and ovaries (gonads). a.​ Primitive germ cells migrate from the yolk sac to the genital ridges. The SRY gene initiates events that lead to the formation of testis cords within the genital ridges. In the absence of the SRY gene, the genital ridges will differentiate into ovaries. 3.​ Describe the formation of external genitalia. a.​ Male external genetailia: genital tubercle elongates, labioscrotal folds fuse to form scrotum, urogenital folds fuse to enclose the penile urethra. The glans plate in the glans penis is solid, canalizes to join the penile urethra b.​ Female external genetailia: genita; tubercle does not elongate, labioscrotal folds dont fuse, urethra is a separate structure, phallus bends inferiorly to become the clitoris, phallic portion or urogenital sinus becomes the vestibule of the vagina, urogenital folds become the labia minora. 4.​ Identify common congenital abnormalities that occur in the reproductive system. a.​ Hypospadias: failure of urethral folds to fuse along the mindline. b.​ Paramesonephric duct anomalies: duplicated uterus within or without double vagina, incomplete fusion of lower segments of ducts c.​ Persistent mullerian duct syndrome: sertoli cells are not secreting testosterone or the signal receptors are down. d.​ Differences in sex development: ovotesticular DSD having sex chromosomes, genetailia and or secondary sex characteristics that are both male and female, 46,XY DSD: genetically male, testes develope, but external genetailia have some  degree of feminization, 46, XX DSD: genetic female, ovaries develop, external genitals masculanized, Primary hypogonadism: gonads do not respond to normal circulation levels of gonadotropins from hypothalamus and pituitary, fail to go through puberty, Males: klienfelter, low sperm count, elongated extremities, sparse hair. Females: turner syndrome, short stature, webbed neck, coarctation of aorta, cervical lymphatic cyst. 5.​ Define pronephros, mesonephros, and metanephros and describe successive development. a.​ Pronephros: primitive kidney that forms a nonfunctional vestigial tubules in the cervical region b.​ Mesonephros: primitive kidney that forms tubules and ducts in the thoracic and lumbar regions. c.​ Metanephros: definitive kidney formed from metanephric mesoderm in the pelvic region 6.​ Explain the significance of intermediate mesoderm in urinary system development. a.​ The intermediate mesoderm forms urogenital ridges that contribute to the formation of portions of the gonads and male genital duct system. The nephrogenic cord portion contributes to the formation of the pronephros, mesonephros, and metanephros. 7.​ Describe the anatomy of the adult urinary system, including structures of the kidney nephron. a.​ The adult urinary system includes: kidneys (filters the blood and removes waste), Ureters (two tubes that carry urine from the kidneys to the bladder), Bladder (organ that stores the urine), Urethra (tube that carries urine out of the body), and Nephrons (filtering units within the kidneys that remove waste from the blood. b.​ The kidney nephron is the functional unit of the kidney including the proximal and distal convoluted tubules, loop of Henle, Bowman capsule and a glomerulus  c.​ 8.​ Summarize positional and vascular changes during kidney development a.​ The kidneys ascend from the pelvis during development. b.​ In the pelvis the kidney brnaches from the common iliac arteries, at aortic bifurcation the kidneys branch from the caudal aorta, in their final position the kidneys branch from the superior abdominal aorta 9.​ Describe the development of the urogenital sinus, including bladder and urethra development. a.​ Between weeks 4-6 the urorectal septum divides the cloaca into the ventral urogenital sinus and the dorsal anorectal canal. The urogenital sinus is subdivided into the presumptive bladder (vesical portion), the female urethra and prostatic/membranous urethra in males (pelvic portion), and the definitive urogenic sinus, vestibule of the vagina and penile urethra in males (phallic portion) 10.​ Define congenital anomalies such as renal agenesis, ectopic kidneys, bifid and ectopic ureter and urachal anomalies. a.​ An ectopic ureter forms an extra ureteric bud that opens anywhere except the bladder. b.​ A bifid ureter forms when the ureteric bud bifricates before entering the metenephric mesenchyme. (often asymptomatic) c.​ Urachal anomalies include: parts of the allantois remaining open and producing a urachal fistula, umbilical urachal sinus, vesicourachal diveticulum, or a urachal cyst. Allabtois collects liquid waste from the embryo and is used in gas exchange. d.​ Renal agenesis is a birth defect where one or both kidneys fail to develop e.​ Ectopic Kidneys is a birth defect where a kidney is located outside of its normal position in the body. Allantois: becomes connection from the bladder to the belly button Pronephros, Mesonephros, Metanephros Nephron: Functional Unit of the Kidney GI Tract 1.​ Explain the formation of the primitive gut tube, its divisions and relationship to primitive mesenteries. a.​ Craniocaudal folding: when the embryo fold along the head to tail axis. Lateral Folding: when the embryo fold laterally brining the sides together. b.​ The primitive gut tube is divided into 3 regions: i.​ Foregut: 1.​ Cranial portion of the gut tube: Esophagus, stomach, Proximal part of the duodenum, liver, gallbladder, pancreas, respiratory system ii.​ Midgut: 1.​ Middle portion of the gut tube: distal part of the duodenum, jejunum, cecum, illeum, appendix, ascending colon, proximal ⅔ of the transverse colon iii.​ Hindgut: 1.​ Caudal portion of the gut tube: distal ⅓ of the transverse colon, sigmoind colon, descending colon, rectum, upper part of the anal canal 2.​ Explain establishment of the gastric curvatures, rotation of the stomach, and establishment of the dorsal and ventral mesogastria. a.​ The stomach starts as a straight tube, as it develops it dialates and bends forming the j shape of the adult stomach. The stomach rotates 90 degrees clockwise around the longitudinal axis. The dorsal mesogastrium is a large sheet of mesentaryt that supports the posterior surface of the stomach (omental bursa forms behind the stomach, greater omentum). The ventral mesogastrium is a smaller sheet of mesentary that supports the anterior surface of the stomach (falciform ligament, lesser omentum). 3.​ Account for the final anatomic relationships that are established between the abdominal viscera and mesenteries. a.​ Dorsal and ventral mesogastria form visceral peritoneal “ligaments” or omenta. Viscera (liver and spleen) develop within the mesogastria. 4.​ Explain development of the abdominal viscera (liver, biliary system, pancreas, spleen) and correlate embryonic structures with adult derivatives. a.​ The liver and biliary system develop from a ventral outgrowth of the foregut endoderm called the hepatic diverticulum. The pancreas develops from two endodermal buds. The spleen develops from mesoderm. 5.​ Describe physiological umbilical herniation, rotation, and retraction of the midgut. a.​ During the 5th week the midget begins to elongate forming the primary intestinal loop with 2 limbs the cephalic limb of the loop (small intestine, duodenum, jejunum, ileum) and the caudal limb of the loop (distal ileum, cecum, appendix,  ascending colon, transverse colon). Loop grows and elongates herniating through the umbilicus, in the umbilicus the cranial limb of the midgut rotates 90 degrees counterclockwise. The cranial limb is on the right and the caudal limb is on the left. During the tenth week the cranial limb will begin to return to the central portion of the abdominal cavity, the caudal limb returns after and rotates 180 degrees counterclockwise. 6.​ Define the terms intraperitoneal, retroperitoneal and secondarily retroperitoneal. a.​ Intraperitoneal: suspended my mesentery, within the peritoneum. b.​ Retroperitoneal: deep in the peritoneum. (bladder or kidneys) c.​ Secondarily retroperitoneal: start as intraperitonea; and later become fully attached to the posterior body wall (duodenum, pancreas, ascending and descending colon) 7.​ Describe the process of cloacal division into urogenital and hindgut portions. a.​ Endoderm extends from the posterior intestinal portal to the cloacal membrane. The lower hindgut is partitioned by a wedge of mesodermal tissue, urorectal septum. The cloaca is partitioned into the ventral urogenital sinus and dorsal rectum and superior anal canal. It then separates the cloacal membrane into a ventra urogenital membrane and a dorsal anal membrane. 8.​ Describe the formation of the upper and lower anal canal at the pectinate line. a.​ The anal membrane ruptures uniting the proctoderm and the hindgut endoderm, this is where the pectinate line is. The pectinate line separates the upper anal canal from the lower anal canal. 9.​ Explain the difference between gastroschisis, omphalocele and umbilical hernia. a.​ Gastroschisis: Defect in the anterior abdominal wall, abdominal viscera protrude withough covering. b.​ Omphalacele: Herniation of bowel or other viscera through the umbilical ring into proximal umbilical cord, covered by peritoneum and amniotic membrane, failure of normal retraction of intestines back into abdominal cavity. c.​ Umbilical Hernia: A small protrusion of bowel through the umbilical ring, covered by skin, the umbilical ring does not close completely. Development of Face and Palate 1.​ Understand that facial primordia are continuous with internal tissue. Recognize internal and external structures that derive from the same tissue (e.g. primary palate & philtrum). a.​ Intermaxillary segments become the philtrum of the lip and the primary plate (internal). b.​ Mandibular prominences become the lower lip, chin, outer cheek c.​ Maxillary prominences become the lateral parts of the upper lip, inner cheek (internal) d.​ Frontal nasal prominences become the forehead, dorsum, apex, alae of the nose, philtrum of the lip, and primary plate (internal). 2.​ Merging Vs. Fusion, clefting a.​ Merging requires continuous mesenchyme between the ecto and endoderm. There is continuous mesenchyme between the facial prominences, merging  derives most of facial development. b.​ Fusion is when 2 separate tissues are brought together. c.​ Clefting occurs when the tissue fails to merge or fuse. 3.​ How do the medial & lateral nasal prominences form? a.​ The medial nasal prominences expand and merge to form the intermaxillary segment, this segment will merge with maxillary prominences on either side b.​ Lateral nasal prominences merge with maxillary prominences, forming the alae (wings of the nose) 4.​ Describe formation of the primary and secondary palates. a.​ The primary palate forms from expansion of deeper portions of the intermaxillary segment, medial growth of facial prominences b.​ The secondary palate is a forerunner of the rest of the adult hard and soft palate, formed by medial growth of facial prominences 5.​ Describe the development of the nasal cavity a.​ The nasal cavity is first indicated by a small nasal pit in the center of the nasal placode. It invaginates to form the larger nasal sac. 6.​ Describe the separation of oral and nasal cavities. a.​ At about 6 weeks a thin oronasal membrane separates the oral and nasal cavity. The nasal cavity enlarges and the oronasal membrane ruptures creating a single oronasal cavity, the primitive choana. A secondary palate is fully formed and joined by 12 weeks, this further separates the oral and nasal cavities. 7.​ Distinguish between the hard and soft palate. a.​ The hard and soft palate are both parts of the roof of the mouth. b.​ The hard palate: is made mostly of bone, it is the front portion of the roof of the mouth. c.​ The soft palate: is made mostly of muscle and connective tissue, back portion of roof of mouth, ends with uvula 8.​ Understand the embryological basis of major face and palate defects: a.​ facial clefts (e.g. oblique, medial/median) i.​ If the maxillary prominence and lateral nasal prominence do not merge, an oblique facial cleft is created. ii.​ When the medial nasal prominences do not completely merge in the region of the intermaxillary segment, a median cleft lip is formed b.​ unilateral & bilateral cleft lip i.​ Anterior clefts: failure of merging between the intermaxillary segment and maxillary prominence. Partial anterior cleft is lip only c.​ primary and secondary cleft palate i.​ Posterior clefts: failure of fusion of the lateral palatine processes 1.​ Complete posterior cleft: affects the secondary palate, hard and soft portions 2.​ Partial posterior cleft: affects any portion of the secondary palate. d.​ abnormal size of the mouth (macro- or microstomia) i.​ Macrostomia (large mouth): occurs with the failure of lateral merging of the maxillary and mandibular prominences. ii.​ Microstomia (small mouth): results from excessive merging of the maxillary and mandibular prominences