Embryonic and fetal growth and development


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Embryonic and fetal growth and development

  2. 2. Objectives At the end of 1 hour interactive lecture-discussion and small group activity, the students will be able to 1. Define related terminologies 2. Identify the different stages of human intrauterine development. 3. Identify the 3 primary germ layers that develop into specific organ systems. 4. Identify and describe the different changes involve in each stage of embryonic development 5. Identify and describe the different changes involve in each stage of fetal development 6. Integrate Christian values in the discussion of the concept of human prenatal development
  3. 3. Related Terminologies  Prenatal  Zygote  Embryo  Fetus  Decidua  Organogenesis  Fertilization  Implantation
  4. 4. STAGES OF HUMAN PRENATAL DEVELOPMENT 1. 2. 3. First 12-14 days = zygote From 15th day up to the 8th week = embryo From 8th week to the time of birth = fetus
  6. 6. PRIMARY GERM LAYERS Ectoderm CNS (brain and spinal cord) PNS Skin, hair and nails Sebaceous glands Sense organs Mucous membranes of the anus, mouth, and nose Tooth enamel Mammary glands Mesoderm supporting structures of The body (connective tissue, bones, cartilage, muscle, ligaments and tendons) dentin of teeth Upper urinary system (kidneys and ureters) reproductive system heart and circulatory system blood vessels lymph vessels Endoderm lining of pericardial, pleura, and peritoneal cavities lining of gastrointestinal tract respiratory tract, tonsils, parathyroid, thyroid, thymus glands lower urinary system (bladder and urethra) lining of pericardial, pleura, and peritoneal cavities lining of gastrointestinal tract respiratory tract, tonsils, parathyroid, thyroid, thymus glands lower urinary system (bladder and urethra)
  8. 8. First Lunar Month           Formation of Fetal Nervous system The spinal cord is formed and fused at the midpoint Lateral wings that will form the body are folded forward to fuse at the midline. Head folds forward and becomes prominent, representing about one third of the entire structure. Arms and legs are budllike structures Rudimentary eyes, ears, and nose are discernable Fetal heart begins to form The digestive tract exists as a single tube until the 3rd week of life Length: 0.75 to 1 cm Weight: 400 mg
  9. 9. Second Lunar Month  All vital organs are formed by the 8th week  The heart, with a septum and valves, is beating rhythmically.  Facial features are definitely discernible.  Arms and legs are developed  External genitalia are present, but sex is not distinguishable by       simple observation The primitive tail is regressing Abdomen appears large because the fetal intestine is growing rapidly Placenta develops fully Sonogram shows gestational sac Length: 2.5 cm (1 inch) Weight: 20g
  10. 10. Third Lunar Month  Kidneys are able to function – urine is formed by the 12th week.  Buds of milk teeth form  Beginning bone ossification  Nail beds are forming on finger and toes.  Spontaneous movements are possible, although they are usually       to faint to be felt by the mother. Sex is distinguishable by outward appearance Fetus swallows amniotic fluid Heartbeat is audible through doppler technology Feto-placental circulation is established by selective osmosis; no direct exchange between fetal and maternal blood. Length: 7 to 8 cm Weight: 45 g
  11. 11. Fourth Lunar Month  Lanugo appears  Buds of permanent teeth form  Heart beat maybe audible with fetoscope  Liver and pancreas are functioning  Fetus actively swallows amniotic fluid  Fetal urine is present in the amniotic fluid  Sex can be determined by ultrasonography  Length: 10 to 17 cm  Weight: 55 to 120 g
  12. 12. Fifth Lunar Month  Vernix caseosa appear  Lanugo covers entire body  Hair forms, extending to include eyebrows and hair on the       head. Meconium is present in the upper intestine Formation of brown fat Definite sleeping and activity patterns are distinguisable Spontaneous fetal movements can bee sensed by the mother Length: 25 cm Weight 223 g
  13. 13. Sixth Lunar Month  Skin markedly wrinkled  Attains proportions of full term baby  Active production of lung surfactant begin  Eyebrows and eyelashes are well defined  Pupils are capable of reacting to light  Eyelids, previously fused since the 12th week, are now     open Hearing can be demonstrated by response to sudden sound Meconium is present as far as the rectum Length: 28 to 36 cm Weight: 550 g
  14. 14. Seventh Lunar Month  Maturation of the lung alveoli  Surfactant can be demonstrated in the amniotic fluid  Testes begin to descend into the scrotal sac from the lower abdominal cavity  The blood vessels of the retina are thin and extremely susceptible to damage from high oxygen concentrations.  Length: 35 to 38 cm  Weight: 1,200 g
  15. 15. Eight Lunar Month  Birth position may be assumed  Fetus is viable  Nails extend to ends of fingers  Subcutaneous fat deposition begins  Length: 38 to 43 cm  Weight: 1, 600 g
  16. 16. Ninth Lunar Month  Amount of lanugo begins to diminish  Most babies turn into a vertex position (head-down presentation during this month.  Sole of the foot has only one or two crisscross creases  Length: 42 to 48 cm  Weight: 1, 800 to 2,700 g (5 to 6 lb)
  17. 17. Tenth Lunar Month      All characteristics of the normal newborn Creases on the soles of the feet cover at least 2/3 of the surface Vernix caseosa is fully formed Length: 48 to 52 cm Weight: 3, 000 g
  18. 18. FOCUS OF FETAL DEVELOPMENT  1ST TRIMESTER – PERIOD OF ORGANOGENESIS  2ND TRIMESTER – Period of continued growth and development; rapid increase in fetal length  3rd TRIMESTER – period of most rapid growth and development due to deposition of subcutaneous fat.
  19. 19. Formation and development of the Embryonic and Fetal Structures
  20. 20. 1. Formation of fetal membrances 1. Chorion – outside embryonic membrane that develops from the trophoblast; contains the chorionic villi at the surface. 2. Amnion – innermost membrane that develops from the interior cells of the blastocysts.
  21. 21. Structure arising from amnion  Amniotic fluid/ Bag of Water (BOW)  Clear albuminous fluid in which the baby floats.  Begins to form at 11-15 weeks gestation.  Alkaline in nature (pH 1.0-1.25) with specific gravity of (1.007-1.025)  Near term is clear, colorless, containing little white specks of vernix caseossa and other solid particles.  Average amount of 500ml-1000ml up to maximum of 1200ml  Sources of are: amniotic cells, fetal urine, and maternal serum.  Functions include:  Cushions the fetus against danger.  Equalize pressure  Prevents adhesion in the sticky skin and umbilical cord compression  fetal movement  thermoregulation  Oral source of fluid for fetus.
  22. 22. Structure arising from amnion  Umbilical Cord/ Funis  21-23 inches or 50-53cm long with 2 ¾” thick.  Has 1 vein (carrying blood from the placental villi to the fetus) and 2 arteries (carrying blood from the fetus back to placental villi). AVA  Approximately 350ml/min blood flow rate.  Covered with gelatinous mucopolysaccharide substance called wharton’s jelly that gives body to the cord and prevents pressure on the vein and arteries.
  23. 23. Structure arising from Chorion Chorionic Villi – projections of the trophoblast that produce human chorionic gonadotropin and begin osmosis of nutrients to the embryo. Parts of Chorionic Villi  Central core – loose connective tissue that contains the fetal capillaries.  Syncytiotrophoblast/ syncytial layer – outer layer of chorionic villi where production or various placental hormones (HCG, somatomammotropin, human placentak lactogen, estrogen, progesterone) during the first 2 months of gestation happen.  Cytotrophoblast or Langerhan’s layer – inner layer of the chorionic villi.    present as early as 12 days of gestation. Protects the growing fetus from certain infectious organisms such as spirochete of syphilis. Disappears between 20th and 24th week of gestation.
  24. 24. Structure arising from Chorion Placenta – rose from chorion together with decidua basalis.  Begins to function by the 4th week of gestation.  Completely independently functioning organ by 14th week  Transmit nutrients and oxygen to the fetus and removes waste and carbon dioxide by diffusion.  The endocrine organ of pregnancy  Estrogen  Progesterone  Human Chorionic Gonadotropin  Human Placental Lactogen/ Human Chorionic Somatomammotropin
  25. 25. Functions of Placenta     Diffusion – movement of molecule from the area of higher concentration to the area of lower concentration. (oxygen, carbon dioxide, sodium, chloride, fat soluble vitamins, liquids including narcotics, anesthetics and barbiturates cross the placenta by simple diffusion. Facilitated Diffusion - placental crossing of some substances that is more rapid and more easily that requires less energy. (glucose) Active Transport – a process that requires energy and action of enzyme to facilitate transport. (essential amino acids and water soluble vitamins) Pinocytosis – absorption by the cellular membrane of microdroplets of plasma and dissolve substances. (Gamma globulin, lipoproteins, phospholipids, and other molecular structures that are too large for diffusion and that cannot participate in active transport cross in this manner.