Langman Medical Embryology Made Easy

OOGENESIS

FOLLICLE MATURATION

BEFORE BIRTH… ↓ nd Primordial Germ Cells (developed in Epiblast; 2 Week) ↓ MIGRATES TO Yolk Sac ↓ th MIGRATES TO Developing Gonads (End of 5 Week) ↓ Oogonia (2N) ↓ DIVIDES (by mitosis) TO FORM Primary Oocyte ↓ Mitosis results to INCREASE NO. OF OOGONIA AND PRIMARY OOCYTE ↓ TOTAL NO. GERM CELLS REACHES MAXIMUM (7 MILLION) ↓ SO, CELL DEATH BEGINS (OOGONIA AND PRIMARY OOCYTE BECOMES ATRETIC) ↓ Surviving Primary Oocytes undergo MEIOSIS I PROPHASE I st DIPLOTINE STAGE (1 arrest) ↓ BIRTH… ↓ 600,000-800,000 Primary Oocyte ↓ ↓ CHILDHOOD… ↓ Primary oocyte becomes Atretic ↓ BEGINNING PUBERTY… ↓ 40,000 Primary Oocyte, fewer than 500 will be ovulated ↓ ↓ PUBERTY… ↓ ↓ ↓ ↓ ↓

BEFORE BIRTH…

MEIOSIS I CONTINUES AND FINALLY COMPLETED ↓ st Secondary Oocyte + 1 Polar Body ↓ ND METAPHASE II OF MEIOSIS II (2 Arrest) ↓ Fertilization””/ No Fertilization ↓ MEIOSIS II CONTINUES AND FINALLY COMPLETED/ secondary oocyte degenerates

↓

↓

↓ Primary Oocyte surrounded by thin layer of follicular cells ↓ Primordial Follicle ↓

↓

↓

↓ ↓ BIRTH… ↓ (FSH) Surrounding follicular cells change from flat to cuboidal and gradually become stratified epithelium forming GRANULOSA CELLS. ↓ GRANULOSA CELLS secrete glycoproteins forming ZONA

PELLUCIDA ↓ Primary Follicle ↓ Cells of THECA FOLLICULA organize into THECA INTERNA and THECA EXTERNA, formation of Antrum ↓

PUBERTY… ↓ Secondary Follicle (LH AND FSH)^^^^ ↓ As Antrum enlarges, granulosa remain intact, thus forming CUMULUC OOPHORUS

↓ Graafian Follicle (surge in LH)

OVARIAN CYCLE

^^^^ OVULATION (Follicular/ Proliferative Phase)

HYPOTHALAMUS ↓ GnRH ↓ GONADOTROPINS ↓ FSH^^ ↓ Stimulates growth and maturation of GRANULOSA CELLS ↓ GC Together with THECA INTERNA ↓ Produce ESTROGEN^^ ↓ Estrogen stimulates Anterior Pituitary Gland ↓ Produce LH^^ ↓ Stimulates FOLLICULAR CELLS ↓ Produce PROGESTERONE

ESTROGEN ↓ Maturation of Secondary Follicle ↓ LH SURGE ↓

^^FSH ↓ Nourishes the follicular cells of PRIMORDIAL FOLLICLE, saving the 25-20 Primary follicle from dying and become atretic

^^ESTROGEN ↓ Uterine Endometrium enter FOLLICULAR/PROLIFERATIVE PHASE / Thinning of cervix mucus to allow passage of sperm

^^LH ↓ Maturation promoting factor / Follicular Rupture and Ovulation ↓ Maturation of secondary follicle and completion of Meiosis I

Secondary follicle forms into Graafian follicle ↑ Collagenase activity/ ↑Prostaglandins level ↓ Digestion of Collage fibers surrounding the follicles/ Local muscular contraction in Ovarian walls ↓ Uterine Tube contract Rhythmically ↓ The PRIMARY OOCYTE is extruded from the ovary together with cumulus oophorus ↓ Fimbrae sweeps over the surface of ovary ↓ SECONDARY OOCYTE is propelled by peristaltic movement or contraction of Uterine Tube ↓ SECONDARY OOCYTE on uterine tube ↓ Cumulus Oophorus rearrange around the zona pellucida ↓ Forming CORONA RADIATA**

“”FERTILIZATION Sperm ↓ Passes the Vagina ↓ Passes the Cervix ↓ Muscular contraction of uterus and uterine tube Uterine tube (2 to 7 hours) ↓ Isthmus of Uterine tube ↓ (Sperm becomes less motile and cease their migration) ↓ CUMULUS OOPHORUS produce chemo-attractants stimulating motility of sperm ↓ Sperm in AMPULLA ↓ CAPACITATION (conditioning of the female reproductive tract; involves epithelial interaction between sperm and mucosal surface of the tube) ↓ Glycoprotein coat and seminal plasma proteins are removed from the acrosome of spermatozoa ↓ SPERM passes through CORONA RADIATA ↓ Acrosome reaction ↓ Sperm passes through ZONA PELLUCIDA (Alters the property of ZONA Pellucida, preventing other sperm from entering) ↓ FUSION OF SPERM AND EGG CELL MEMBRANES

**CORPUS LUTEUM (SECRETORY PHASE) If oocyte is not fertilized…

Remains of the Ruptured Follicle (GRANULOSA CELLS + THECA INTERNA) ↓ Vascularized by surrounding vessels ↓ Develops into LUTEAN CELLS ↓ CORPUS LUTEUM ↓ CORPUS LUTEUM reaches maximum development approx. 9 days after ovulation ↓ CORPUS LUTEUM shrinks and produce PROGESTERONE ↓ Becomes CORPUS ALBICANS ↓ Venules and sinusoidal space become packed with blood cells/ extensive diapedesis in blood tissues ↓ Shedding of Endometrium (Menstruation)

If oocyte is fertilized… Remains of the Ruptured Follicle (GRANULOSA CELLS + THECA INTERNA) ↓ Vascularized by surrounding vessels ↓ Develops into LUTEAN CELLS ↓ CORPUS LUTEUM ↓ CORPUS LUTEUM does not degenerate (Under influence of HCG) ↓ Develops into CORPUS LUTEUM of PREGNANCY ↓ th Produce PROGESTERONE (until end 4 month that the uterus is ready for implantation) ↓ IMPLANTATION ↓ Uterine glands and arteries become coiled and tissues become succulent

CLEAVAGE

SPERMATOGENESIS

PRIMORDIAL GERM CELLS is at Sex cords At Birth Uterine Tube… ↓ 2 Cell Stage ↓ 4 Cell Stage (formation of blastomeres) ↓ COMPACTION (Blastomeres maximize their contact with each other; segregates inner cell mass from outer cell mass) ↓ 8 Cell Stage ↓ 16 Cell Stage – Morula ↓ Morula enters Uterine Cavity… ↓ Fluid begins to penetrate zona pellucida ↓ Forming BLASTOCOELE ↓ Formation of inner cell mass and outer cell mass ↓ BLASTOCYST ↓ Zona pellucida disappears ↓ IMPLANTATION (Trophoblastic cells penetrate epithelial cells of Uterine Mucosa)

↓ Before Puberty… Sex cord obtain lumen and form Seminiferous tubules ↓ PG develops into SPERMATOGONIAL STEM CELLS ↓ Differentiate to SPERMATOGONIA TYPE A ↓ Divides by mitosis to form SPERMATOGONIA TYPE B ↓ Divides by mitosis to form PRIMARY SPERMATOCYTE ↓ Meiosis I prolonged ↓ Puberty ↓ Meiosis I completed ↓ Forms SECONDARY SPERMATOCYTE ↓ Meiosis 2 completed ↓ Forms SPERMATIDS ↓ Spermiogenesis (1. Formation of acrosome, 2. Condensation of nucleus, 3. Formation of neck, midpiece and tail and 4. Shedding of cytoplasm) ↓ Mature Spermatozoa ↓ Lumen of Seminiferous Tubules ↓ Epididymis

2

Day 8… 

nd

Week of Development (FORMATION OF BILAMINAR DISC)

Day 9…

Day 11 and 12…

Blastocyst attaches its outer cell mass in the epithelium of Endometrial Stroma

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Blastocyst is partially embedded in the endometrial stroma



Blastocyst is completely embedded in endometrial stroma

Blastocyst forms: Trophoblast (Outer Cell Mass)  Cytotrophoblast (mononucleated)



Penetration defect is closed by FIBRIN COAGULUM



Surface epithelium almost entirely covers the original defect in the uterine wall



Appearance of LACUNAE in syncytiotrophoblast





Blastocyst cavity becomes PRIMITIVE YOLK SAC

Syncytiotrophoblast penetrate deeper into the stroma and erodes endothelial lining → Maternal blood enters lacunae → Establishment of UTEROPLACENTAL CIRCULATION



Hypoblast forms the EXOCOELOMIC MEMBRANE (Heuser’s Membrane) – lining of primitive yolk sac

 o



o

o

Syncytiotrophoblast (multinucleated)

Embryoblast (Inner Cell Mass)  Hypoblast (Cuboidal cells)  Epiblast (Columnar cells)  Amnioblast Blastocyst cavity

Day 13…



  o o

Exocoelomic Membrane becomes EXTRAEMBRYONIC MESODERM SOMATOPLEUR (Somatic Mesoderm) SPLANCHNOPLEUR (Visceral Mesoderm)

Primitive Yolk Sac becomes the SECONDARY/ DEFINITE YOLK SAC Extraembryonic coelom expands to form CHORIONIC CAVITY

rd

3 WEEK (GASTRULATION & NEURULATION) Day 14   o o o

Formation of PRIMITIVE STREAK Migration of Epiblast cells Towards the hypoblast – ENDODERM Epiblast and newly created endoderm – MESODERM Remains in the epiblast – ECTODERM *These cells spread laterally and cranially

Day 16 - 18  Formation of NOTOCHORD (Basis of axial skeleton)  Elongation o Cranial end (from prechordal plate) o Caudal end are added (in primitive pit) o Primitive pit forms indentation in the epiblast – neurenteric canal temporarily connects the amniotic and yolk sac cavities o CLOACAL MEMBRANE is formed at the caudal end

 o o

o

Mesoderm differentiates into: PARAXIAL MESODERM (midline) LATERAL PLATE MESODERM (lateral)  Mesoderm covering the Amnion – Somatic or Parietal Mesoderm  Mesoderm covering the Yolk Sac – Splanchnic or Visceral Mesoderm  Both mesoderm forms the INTRAEMBRYONIC CAVITY INTERMEDIATE MESODERM (connects paraxial and lateral plate mesoderm)

NEURULATION Day 19 

Day 20 Formation of NEURAL PLATE

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Day 23 Neuroectoderm becomes elevated forming the NEURAL FOLDS

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Day 25 Neural folds fuse cranially and caudally forming the NEURAL TUBE

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Day 28 Closure of the ANTERIOR NEUROPORE (18 – 20 somite stage)

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Closure of POSTERIOR NEUROPORE (25 somite stage)

th

4 WEEK (ORGANOGENESIS) ECTODERM NEURAL TUBE o 

Cranial region – forms the BRAIN VESICLES Prosencephalon (FOREBRAIN) o Telencephalon – CEREBRUM o Diencephalon – OPTIC CUP, THALAMUS, HYPOTHALAMUS and EPIPHYSIS



Mesencephalon (MIDBRAIN)

NEURAL CREST CELLS o

o 



o

RHOMBOCEPHALON (HINDBRAIN) o Metencephalon – CEREBELLUM, PONS o Myelencephalon – MEDULLA OBLONGATA Caudal region – forms the SPINAL CHORD



They migrate into : CRANIAL NEURAL FOLDS to form:  CRANIOFACIAL SKELETON  NEURONS FOR CRANIAL GANGLIA  GLIAL CELLS Mesoderm in 2 pathways: DORSAL PATHWAY  MELONOCYTE VENTRAL PATHWAYS  SENSORY GANGLIA  ENTERIC NEURONS  SCHWANN CELLS  ADRENAL MEDULLA CELLS

MESODERM PARAXIAL MESODERM SOMITES SCLEROTOME o

o

Ventromedial forms the cartilage, tendons and bones Vertebrae Primary Curves • THORACIC CURVE • SACRAL CURVE Secondary Curves • CERVICAL CURVE (develops when a child learns to hold up his head) •LUMBAR CURVE (develops when a child learns to walk)

o

Intervertebral disc

o

Together with Lateral Plate mesoderm forms the COSTAL CARTILAGE

o

DERMATOME Remains in o the middle –forms the dermis of back

o

Dorsomedial & Ventrolateral – forms the segmental muscles

Ventrolateral lip o INFRAHYOID, ABDOMINAL WALL, LIMB MUSCLES

 o

LATERAL PLATE MESODERM Somatic mesoderm Splanchnic Mesoderm

INTERMEDIATE MESODERM Metanephric Ureteric Bud Mesodern

MYOTOME

DERMOMYOTOME 

SOMITOMERES

Dorsolateral lip Muscles of the back, shoulder girdle and intercostal muscles

o Cranially (in association with neural plate) – forms the NEUROMERES and then into MESENCHYME OF THE HEAD o Caudally to form the SOMITES which will form the AXIAL SKELETON

 w/ ectoderm –  dermis of skin in body wall, connective tissue of limbs   w/ sclerotome and myotome – costal cartilage, limb o muscles and most body wall o muscles  surround in intraembryonic cavity – mesothelial and serous membranes 

MANUBRIUM, STERNEBRAE XIPHOID PROCESS



Together with neural crest cells form SMOOTH MUSLES

BONY PART OF THE RIBS

w/ embryonic endoderm – wall of Gut Tube Hemangioblast →blood islands → blood cells Stroma of glands Visceral muscles, connective tissue and Peritoneal components of the gut

o Bowman’s capsule o Proximal Convulated Tubule

o Ureter o Renal Pelvis o Major Calyx

o Loop of Henle o Distal Convulated Tubule

o Minor Calyx

FOREGUT  Dorsal portion of the Respiratory Diverticulum forms the ESOPHAGUS Fusiform dilation of the foregut forms the STOMACH

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The terminal part of the foregut and the cephalic part of the midgut forms the DUODENUM

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Outgrowth of the endodermal epithelium at the distal end of the foregut forms the LIVER

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Small ventral outgrowth formed by the bile duct forms the GALLBLADDER

o

Formed from the two buds of the endodermal lining of duodenum is the PANCREAS

o o

Epithelial lining of digestive tract Hepatocytes, endocrine and exocrine glands of pancreas

ENDODERM MIDGUT  Cephalic limb of the primary intestinal loops develop into DISTAL PART OF DUODENUM, JEJUNUM AND PART OF ILEUM

HINDGUT  DISTAL 1/3 OF TRANSVERSE COLON 

DESCENDING COLON

Caudal limb of the primary intestinal loops becomes the LOWER PORTION OF ILEUM, CECUM, APPENDIXASCENDING COLON AND PROXIMAL 2/3 OF TRANSVERSE COLON



SIGMOID



RECTUM

*formed from rapid elongation of the gut and its mesentery

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UPPER PART OF ANAL CANAL (derived from endoderm of hindgut and ectoderm of proctodeum)

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INTERNAL LINING OF BLADDER AND URETHRA



o

*degeneration of cloacal membrane establish continuity between upper and lower part of anal canal

Orientation of BODY PARTS LIMBS o   o  

STOMACH st

FORELIMBS (1 ) Rotates 90 degree laterally Extensor muscles lie laterally and posteriorly, thumbs on lateral side nd

HINDLIMBS (2 ) Rotates 90 degree medially Extensor muscles at the anterior, toes at the medial side

SEGMENTATION OF THE LIMBS  First circular constriction separates distal segment (foot/hand) from proximal segment (legs)  Second circular constriction divides proximal portion into two segments (the thigh and the legs)

DUODENUM



90 DEGREE CLOCKWISE ROTATION AROUND THE LONGITUDINAL AXIS



ROTATION OF STOMACH ON ANTEROPOSTERIOR AXIS

o o o

Left side of the stomach face anteriorly Right side of the stomach face posteriorly Greater Curvature of the Stomach (formed because posterior wall of stomach grows faster than anterior wall)

o

Duodenum forms a C shaped loop and rotates to the right Swings duodenum from midline to right of abdominal cavity



ROTATION ON THE ANTEROPOSTERIOR AXIS

o o

Caudal or pyloric part moves right, upward Cephalic or cardiac portion moves left downward

o

FINGERS and TOES Distal portion thickens and forms APICAL ECTODERMAL RIDGE (AER) AER inducts the adjacent mesenchyme causing it to remain undifferentiated, rapidly, proliferating cells called PROGRESSIVE ZONE Cell death in AER separate ridges into 5 parts o FEET/HANDS  Terminal portion becomes flattened to form HAND AND FOOT PLATES o

  

1

ST

PHARYNGEAL ARCH

2

ND

PHARYNGEAL ARCH RD PHARYNGEAL ARCH 3 PHARYNGEAL ARCH

TH

4

AND 6

TH

PHARYNGEAL ARCH

(Hyoid arch) o

Maxillary Process (Dorsal) PREMAXILLA, MAXILLA, ZYGOMATIC BONE, part of TEMPORAL BONE

o

Mandibular Process (Ventral) INCUS, MALLEUS



 o

o

1

ST

o

FACIAL NERVE

o

LOWER PART OF THE BODY OF HYOID BONE, GREATER HORN OF HYOID BONE

o

THYROID, CRICOID, ARYTENOID, CORNICULATE CUNEIFORM CARTILAGE OF LARYNX

o

SUPERIOR LARYNGEAL BRANCH OF VAGUS NERVE (4TH Arch)

o

RECURRENT LARYNGEAL BRANCH OF VAGUS NERVE (6TH Arch)

TRIGEMINAL NERVE o

 o

STAPES, STYLOID PROCESS, TEMPORAL BONE, STYLOHYOID LIGAMENT, LESSER HORN and UPPER PART OF THE BODY OF HYOID BONE

GLOSSOPHARYNGEAL NERVE

1ST PHARYNGEAL CLEFTS EXTERNAL AUDITORY MEATUS

PHARYNGEAL POUCH

2

ND

PHARYNGEAL POUCH

PAHRYANGEAL POUCH RD 3 PHARYNGEAL POUCH

TH

4

PHARYNGEAL POUCH

Palatine Tonsils o o

TYMPANIC MEMBRANE (Distal) EUSTACHIAN TUBE (Proximal)

o o

INFERIOR PARATHYROID GLAND (Dorsal) THYMUS (Ventral)

SUPERIOR PARATHYROID GLAND (Dorsal) o ULTIMOBRANCHIAL BODY (Ventral)  Parafollicular Cells of Thyroid Gland  Calcitonin o

TONGUE 

MESODERM OF 1ST PHARYNGEAL ARCH

TH

MESODERM OF 2ND, 3RD AND 4TH PHARYNGEAL ARCH

Posterior Part of the 4 Arch

LATERAL LINGUAL SWELLING

1ST MEDIAL SWELLING

2ND MEDIAN SWELLING

3rd MEDIAN SWELLING

Anterior 2/3 of TONGUE

Anterior 1/3 of TONGUE

Posterior Root of TONGUE

EPIGLOTTIS

MAXILLARY PROMINENCE 

Merge with 2 MEDIAL NASAL PROMINENCE

 UPPER LIP

FRONTONASAL PROMINENCE

Merge with the INTERMAXILLARY SEGMENT

MANDIBULAR PROMINENCE Merge across the midline

UPPER JAW COMPONENT

LABIAL COMPONENT

PALATAL COMPONENT

LATERAL NASAL PROMINENCE

MEDIAL NASAL PROMINENCE

4 INCICOR TEETH

PHILTRUM OF UPPER LIP

TRIANGULAR PRIMARY PALATE

SIDE OF NOSE AND CHEEKS

CREST AND TIP OF NOSE

LOWER LIP

2 Month nd 2 Month th th (5 week – 8 week) LIMBS AND HEAD RD

th

th

th

th

  

INCREASE IN HEAD SIZE FORELIMBS APPEAR as paddle shaped buds HINDLIMBS appear later

       

Slowdown in the growth of the head compared to the rest of the body FACE becomes more HUMAN –LIKE EYES from lateral position moves to the ventral portion of the head Ears comes to lie at their definite position in the head Limbs reach their relative length Primary ossification are present in long bones and skull External genitalia develop to such degree that the sex of the fetus can be determined Large swelling (Herniation) has withdrawn into the abdominal cavity

  

Fetus lengthens rapidly Weight increase a little Fetus is covered with fine hair (lanugo), eyebrows are visible

  

Movements of fetus can be felt by the mother Weight increase rapidly Fetus swallows its own amniotic fluid (400 mL a day) – FETAL urine is added daily to the amnion

 

Skin is reddish and wrinkled because lack of underlying connective tissue Fetus born in this month cannot survive since Respiratory and Nervous System has not yet sufficiently differentiated

 

Fetus obtains well rounded contours as a result of fat deposition The skin is covered with whitish fatty substance (Vernix caseosa) composed of secretory products of sebaceous glands



Skull has the largest circumference of all parts of the body

th

5 Month (17 – 20 weeks) WEIGHT

6 Month (21 RED SKIN 7 Months (25 WHITE SKIN

Development

th

4 ( 13 – 16 weeks) LENGTH

th

MONTH TO BIRTH

th

3 Month ( 9 – 12 week) FULL DEVELOPMENT OF ORGANS

th

nd

ST

th

TH

24

weeks)

th

- 28 weeks)

th

9 Month ( 33th - 36 weeks) FETUS READY FOR DELIVERY

2

nd

MONTH   

Cytotrophoblastic cells invades (ENDOVASCULAR INVASION) the terminal ends of SPIRAL ARTERIES This transforms SPIRAL ARTERIES from small diameter, high resistance vessels to large diameter, low resistance vessels Spiral arteries release blood into the INTERVILLOUS SPACE – derived from lacunae of Syncytiotrophoblast; filled with maternal blood

TH

4

CHANGES IN THE TROPHOBLAST/ PLACENTA MONTH      

  o o o o

Cytotrophoblastic cells and connective tissue cells disappears due to increase in diameter of villi The SYNCYTIUM and ENDOTHELIAL WALL OF BLOOD VESSELS are the only layers that separate maternal and fetal circulation Villi covers the surface of the CHORION Villi grow and expand to form CHORION FRONDOSUM Villi on abembryonic region degenerate forming CHORION LEVAE CHRORION LEVAE comes in contact with DECIDUA PARIETALIS on the opposite side of the uterus and fuse, obliterating the uterine lumen Amnion expands, and come in contact with Chorion, obliterating the CHORIONIC CAVITY; yolk sac shrinks and gradually obliterated Placenta produce: PROGESTERONE to maintain pregnancy (synthesized in SYNCYTIAL TROPHOBLAST) ESTROGEN just before end of pregnancy to promote uterine development and growth of mammary glands hCG to maintain Corpus luteum Placental lactogen which gives fetus priority on maternal blood glucose and makes mother diabetogenic; promotes breast development for

TH

5

MONTH  PLACENTA ENLARGES with growth of the fetus and expansion of Uterus not due to further penetration into maternal tissues but due to arborisation of existing villi



EFFACEMENT



o

Uterine contracts, amniotic sac s forced against the cervical canal like a wedge If memebrane is ruptured, pressure will be exerted by the presenting part of the fetus, usually the HEAD

o o

o

PARTURITION DELIVERY OF THE FETUS Uterus contracts Increased intraabdominal pressurefrom contraction of Abdominal Muscles



DELIVERY OF THE PLACENTAL MEMBRANES

o o

Uterine contractions Abdominal muscle contraction

PLACENTA Placenta is composed of:  o

CHORION FRONDOSUM (Fetal Component) – derived from TROPHOBLAST and EXTRAEMBRYONIC MESODERM Bordered by CHORIONIC PLATE

DECIDUA BASALIS (Maternal Component) – derived from UTERINE ENDOMETRIUM o Bordered by DECIDUAL PLATE o Contains compartments called COTYLEDONS – maintain its contact with INTERVILLOUS SPACE through DECIDUAL SEPTA Function: 

   

Exchange of gases (simple diffusion) Exchange of nutrients Transmission of Maternal Antibodies Hormone Production (hCG , progesterone, estrogen and placental lactogen)

Full Term Placenta:  Discoid  15 to 25 cm in diameter  3 cm thick  Weighs 500 to 600 grams  Form from uterine wall at birth  Expelled 30 minutes after birth On MATERNAL SIDE:  Contains 15 TO 20 cotyledons covered by decidua basalis On FETAL SIDE: 

PLACENTA is covered by CHORIONIC PLATE

 CHORIONIC VESSELS converge toward the umbilical cord  CHORION is covered by AMNINON 4 Layers of Placental Membrane:  Endothelial lining of Fetal Vessels  Connective Tissue on Villous Core  Cytotrophoblastic layer  Syncytium The Amniotic Fluid     o o o

Derived from maternal blood Produced by amniotic cells Clear, watery fluid replaced every 3 hours Normal amount: 10 weeks – 30 mL 20 weeks – 450 mL 37 weeks – 800 – 1000 mL

Function:   

Absorbs jolt Prevents adherence of embryo to the amnion Allow fetal movements

The Umbilical Cord  o o  o o

Distally, contains : Yolk Stalk Umbilical vessels Proximally contains: Intestinal loop Remnant of Allantois

th

Resource: Langman’s MedicalEmbryology, 11 Edition Compiled and condensed by: Ma. Theresa Monje August 21, 2012