Presentation is loading. Please wait.

Presentation is loading. Please wait.

Lecture 5 General med_2nd semester Development of external form of the embryo and fetus. The rule of Hasse Uterine growth during pregnancy Marks of the.

Similar presentations


Presentation on theme: "Lecture 5 General med_2nd semester Development of external form of the embryo and fetus. The rule of Hasse Uterine growth during pregnancy Marks of the."— Presentation transcript:

1 Lecture 5 General med_2nd semester Development of external form of the embryo and fetus. The rule of Hasse Uterine growth during pregnancy Marks of the mature and full-term fetus Multiple pregnancy: mono- and dizygotic twins; arrangements of fetal membranes in twins Position, posture and presentation of the fetus

2 Development of the external form of the embryo and fetus 1st month: growth of developing embryo is accompanied by changes of its shape and size the human development begins by spherical zygote that mitotically divides and gives rise to 2-,4-,8-cell stage,- a morula up to the morula stage all blastomeres are totipotent more differentiated stage than morula is a blastocyst composed of two cell lines: trophoblast and embryoblast

3 the embryoblast is soon differentiated into germ layers - the ecto- and endoderm by the third week, the formation of the third germ layer mesoderm begins the embryo becomes trilaminar disc called the embryonic disc

4 the mesoderm then differentiates into somites, intermediate and lateral mesoderm

5 by day 10, development of fetal membranes run by the end of the first month, the embryo becomes to form a tube that is C - shaped curved a convexity of the embryo is adjacent dorsally and the embryonic body can divide into three parts: head, rump and tail embryo is connected via omphalomesenteric duct with vitelline sac length of the embryo is lesser than 1 cm

6 2nd month: the cephalic region (future head) is large with 5 obvious prominences, from which a face of the embryo develops in the future cervical region, 4 pairs of branchial arches and between them branchial grooves lay down simultaneously limb buds differentiate and development of limbs starts (development of the upper limb precedes development of the lower one) at the end of this month the head is more rounded and shows human characteristics, external genitalia still have sexless appearance the embryo is about 20 mm long the term the embryo does not use longer and concept is termed the fetus

7 3rd month: main developmental processes are completed head is large and constitutes almost half of the fetus but later growth of body length accelerates and head becomes smaller face is broad, the eyelids are developed but they close to the end of this month upper limb reaches its final relative length the external genitalia are well developed and the sex of the fetus is possibly to identify in liver and then in spleen, the hematopoiesis begins fetus starts to excrete urine (into amniotic fluids) length - 9 cm, weight 20 grams 4th month: fetus grows rapidly in this period, many bones begin ossification process and may be identified by imaging methods length - 16 cm and weight 120 grams

8 5th month: lower limbs reaches their final relative proportion the skin is covered with a greasy cheese - like material with protective function known as vernix caseosa and with fine hairs called lanugo mother feels the first fetal movement - quickening the length 25 cm, weight cca 300 grams 6th month: the skin is usually wrinkled as the layer of the subcutaneous fat is missing it is translucent and pink-reddish coloured as blood capillaries and vessels are seen production of surfactant begins in lungs fetus is 30 cm long and weighs 650 grams 7th month: accumulation of the subcutaneous fat starts, head and lanugo hairs well developed eyes reopen CNS is able to control rhythmic breathing movements and body temperature so that the fetus may survive if born prematurally length - 35 cm, weight grams 8th month: continuation of accumulation of subcutaneous fat - the skin becomes pink and smooth; the descent of testes usually begin length - 40 cm, weight grams

9 9th month: nails reach to the ends of distal phalanges, hairs are short, skin is always pink and smooth the descent of the testes is completed length - 45 cm, weight grams 10th month: individual body parts show usual proportions hairs are minimally 1 cm long, labor of the fetus --- newborn fetus is 50 cm long and weighs grams Rule of Hasse used for estimation of fetal age of a unknown fetus (important in forensic medicine) from the 3rd to 5th month, the length of fetus is equal with the second power of respective month (9, 16, 25 cm) from the 6th to 10th month, the length of fetus is equal with product 5 x respective month (30, 35, 40, 45, 50 cm)

10 Uterine growth during pregnancy the uterus of a nonpregnant female lies in the pelvis minor, during pregnancy it increases in size to accommodate the growth of the fetus the increasing uterus is to touch through the ventral wall of the abdomen   3rd month - uterine fundus corresponds to the superior aspect of the pubic symphysis   5th month - uterine fundus occupies the half distance between the umbilicus and pubic symphysis   6th month - uterine fundus is just in the level of the umbilicus   8th month - uterine fundus lies at the half distance between the umbilicus and xiphoid process   9th month - uterine fundus is just in level of the xiphoid process   10th month - uterine fundus descends and is located for about two fingers below the xiphoid process the increase in size of the uterus results from hypertrophy of preexisting muscle cells

11 Estimation of the date of birth the date of birth is calculated according to the day of fertilization or the onset of the last normal menstrual period in the first case, birth follows after 266 days after estimated day of fertilization (38 weeks = 8 3/4 calendar months= 9 1/2lunar months) in the second case, birth follows after 280 days after onset of the last menstrual period (LMP) (40 weeks =91/4 calendar month=10 lunar month)

12 Marks of the mature (full-term) fetus in the human, the pregnancy lasts 280 days or 40 lunar weeks from the 1st day of LMP (266 days or 38 weeks after fertilization) fetuses born ± 10 to 14 days before or after term are called mature or full-term if they born before 37th week - premature and born after 42 weeks - postmature ones criteria or signs of maturity of the fetus: are major and the auxiliary ones Major marks: length of fetus - about 50 cm, weight of fetus to 3500 g, in males testes are within the scrotum, in females labia minora are covered with labia majora dimensions of the new-born head should be in norm ( head circumference to circumference of shoulders or chest should be 35:34)

13 Auxiliary marks:   skin of the fetus is pink   only residues of fine lanugo hairs are found   hairs on head are at minimal 1 cm long   nails have grown beyond the tips of the digits   in the distal epiphysis of the femur is a distinct ossification centre   baby is plump and cries Rule of Hasse used for estimation of fetal age of a unknown fetus (important in forensic medicine)  from the 3rd to 5th month, the length of fetus is equal with the second power of respective month (9, 16, 25 cm)  from the 6th to 10th month, the length of fetus is equal with product 5 x respective month (30, 35, 40, 45, 50 cm)

14 Dimensions of head in newborns are transverse and longitudinal transverse dimensions: - bitemporal distance - 8 cm (there is a distance of two points on the coronal suture lying each other as far as possible) - biparietal distance cm (there is a distance between the centres of both parietal tubera)

15 Dimensions of head in newborns longitudinal dimensions: - frontooccipital distance - 12 cm (there is a distance between the centre of the forehead and external occipital protuberance), frontooccipital circumference - 34 cm, - distance subocciput-bregma cm (from bregma to the external occipital protuberance), circumference subocciput-bregma 32 cm, - mentooccipital distance cm (from the centre of the chin to the external occipital protuberance), mentooccipital circumference 35 to 36 cm.

16 Multiple pregnancies: Mono- and dizygotic twins; arrangement of fetal membranes in twins multiple pregnancies occur in the human labor of twins falls on 90 pregnancies triplets on 90 x 90 pregnancies (90 2 ) quadruplets on 90 x 90 x 90 (90 3 ) pregnancies Twins may be of two categories: dizygotic or fraternal - two zygotes monozygotic or identical - one zygote cca 2/3 of all twins are dizygotic

17 Dizygotic twins: Dizygotic twins: result from fertilization of two ova by two different spermatozoa three possible ways of origin are supposed: 1) both ova have developed in the same follicle - fertilized simultaneously 2) the ova derive from two follicles in the same ovary 3) one ovum was developed in the left and the other in the right ovary dizygotic twins may be of the same sex or different one genetically, they are no more alike than brothers or sisters born at different times dizygotic twins always have separate fetal membranes: two amnions two chorions + two placentas chorions and placentas may be fused in various extent

18 Monozygotic twins are always of the same sex because result from fertilization of one ovum they are genetically identical and very similar in physical appearance an arrangement of fetal membranes in these twins depends upon the twinning time twinning may occur in:   immediately after the first mitosis of zygote - twinning on two-cell stage (the zona pellucida is precociously dissolved, blastomeres then loose close contact and may develop independently each other each fetus has proper fetal membranes (separate)

19 Monozygotic twins   around the end of the first week in time developing of inner cell mass (it can develop two embryonic primordia or the inner cell mass or embryoblast secondary divides into two parts) subsequently, two embryos develop, each in its own amniotic sac but within one chorionic sac - such twins have two amnions one common chorion and placenta

20 Monozygotic twins   around the end of the second week (between day ) if the duplicated primitive streak and chordomesodermal process develop twins have common all fetal membranes one common amnion one common chorion and placenta

21 Position, posture and presentation of the fetus (in the uterus) Position of the fetus (situs fetus) is defined as a relation of its longitudinal axis to the longitudinal axis of the uterus 3 positions are distinguished: - longitudinal position - both axes run parallel - in 99,5 per cent - transverse position - both axes are rectangle - oblique position - axes are passing (instable position) The longitudinal position: by head (96,5 %) or by breech (pelvic end of the fetus) - 3 %. The back of the fetus is most often oriented to the left edge of the uterus Posture of the fetus (habitus fetus) is defined as a relation of fetal body parts to each other may be regular and irregular regular posture = the head is in flexion, the chin is in close contact with the chest, upper and lower limbs are flexed in both articulations and are folded

22 Presentation of the fetus (praesentatio fetus) is defined as a relation of the fetal body part to the pelvic aditus cases that occur: - cephalic presentation - is physiological or normal - breech presentation - by pelvic end of the fetus - rare, - foot or knee presentation - very rare, - malpresentation - any abnormal presentation

23

24 Dimensions of the female pelvic aditus:

25


Download ppt "Lecture 5 General med_2nd semester Development of external form of the embryo and fetus. The rule of Hasse Uterine growth during pregnancy Marks of the."

Similar presentations


Ads by Google