Infundibulum in Female Reproductive System

Infundibulum

• Distal part of the fallopian tube, trumpet-shaped, swollen at ovulation.
• Approximately 2 cm long, covered by fimbria, which guide the ovum into the fallopian tube.
• Functions to produce, mature, and discharge ova (egg cells).
• Ovaries secrete estrogen and progesterone, initiating and regulating the menstrual cycle.
• Removal of ovaries before puberty affects maturation and maintenance of secondary sex characteristics, leading to a male-pattern pubic hair distribution.

Uterus

• Hollow, thick-walled muscular organ with variable size, shape, and weight.
• Typical size: approximately 5 to 7 cm long and 5 cm wide when non-pregnant; weighs 60g.
• Shape varies: pear-shaped when non-pregnant and ovoid when pregnant; olive shape during childhood.
• After pregnancy, uterus size changes to about 9 cm long, 6 cm wide, 3 cm thick, and weighs approximately 80g.
• Consists of two layers:
  • Basal Layer: unaffected by hormones.
  • Glandular Layer: influenced by estrogen and progesterone, supports pregnancy, sheds during menstruation if no pregnancy occurs.
• Myometrium: middle muscle layer constricts the fallopian tubes to prevent menstrual retrograde flow and maintains internal cervical closure during pregnancy.
• Perimetrium: outermost layer providing strength and support.

Uterine Divisions

• Body of Uterus (Corpus): expands to accommodate the growing fetus.
• Fundus: palpated to assess uterine growth and contraction strength.
• Isthmus: short segment connecting body to cervix, site for cesarean section incision.

Menstrual Cycle and Fertilization

• Decreased progesterone leads to menstrual flow; FSH initiates follicle development.
• Estrogen produced by follicles stimulates GnRH, FSH, and LH secretion, enhancing estrogen production in a positive feedback loop.
• LH triggers ovulation and formation of the corpus luteum.
• If fertilization does not occur, progesterone secretion declines, resulting in menstruation.
• Mittelschmerz: mild abdominal pain marking ovulation day.

Fertilization Process

• Pregnancy begins when sperm meets the egg.
• Sperm produced in testes, eggs reside in ovaries.
• Hormones regulate the menstrual cycle and egg maturation.
• Ovulation occurs when a mature egg is released from the ovary.
• Sperm can swim to locate and fertilize the egg post-ejaculation.
• Fertilized egg moves to the uterus for implantation.
• Without fertilization, the uterine lining is shed during menstruation.

Sperm Characteristics

• Male reproductive cell measuring about 0.05 mm with a head, middle piece, and tail.
• Contains 23 chromosomes: 22 autosomes and 1 sex chromosome, determining offspring sex when fused with X chromosome.

Progesterone Functions

• Maintains endometrial lining during pregnancy.
• Reduces uterine muscle contractility to prevent premature labor by altering electrolyte balance.

Fetal Membranes

• Surround the fetus, contributing to the shiny appearance of the placenta.
• Chorionic Membrane: outermost fetal membrane.
• Amniotic Membrane: consists of two layers (chorion and amnion), fuses over pregnancy, and no nerve supply.
• Provides support for amniotic fluid, essential for fetal development.

Placental Hormones

• Human Chorionic Gonadotrophin (HCG): detectable in urine and blood shortly after implantation; stimulates corpus luteum to maintain endometrium, serving as a pregnancy test marker.
• Around the 8th week of pregnancy, placenta begins progesterone production; decline in HCG levels occurs post-placental formation, with HCG undetectable 1-2 weeks after delivery.### Hormones and Functions
• Human Chorionic Somatomammotropin, also known as Human Placental Lactogen, is produced starting at the 6th week of pregnancy, peaking at term.
• Prostaglandins, initiated by phospholipids, may trigger the onset of labor.

Amniotic Fluid

• Forms within the amniotic cavity, surrounding the embryo.
• Typical volume ranges from 800ml to 1200ml, contains fetal urine, lanugo, epithelial cells, and subaqueous materials.
• Maintains a pH of 7.2 and specific gravity of 1.005 - 1.025.
• Oligohydramnios is defined as less than 300ml, whereas polyhydramnios exceeds 2000ml.
• Fluid is not stagnant; the fetus swallows amniotic fluid, which is absorbed into the fetal bloodstream and exchanged with the mother.
• Adequate fluid levels ensure proper kidney function of the fetus.

Umbilical Cord Structure

• Formed from the amnion and chorion, establishing circulatory communication between mother and fetus.
• Transports oxygen and nutrients from the placenta to the fetus and returns waste products.
• Composed of 1 vein (carrying blood to the fetus) and 2 arteries (returning blood to the placenta), associated with potential congenital disorders.
• Average length is about 53cm (21in.) and thickness is around 2 cm.
• Blood flow rate through the umbilical cord reaches 350ml/min at term.
• Wharton’s jelly provides cushioning to protect the vein and arteries.

Fetal Development Milestones

End of 4th Gestational Week

• Length ranges from 0.75 to 1 cm and weight is approximately 400 mg.
• Formation of spinal cord and notable head size relative to the body.
• Development of rudimentary heart and budlike structures for arms and legs.

End of 8th Gestational Week

• Length reaches about 2.5 cm (1 inch) and weight is 20 gm.
• Organogenesis is completed with a rhythmically beating heart and developing facial features.
• External genitalia are present but not distinguishable by simple observation.

End of 12th Gestational Week

• Length measures 7 to 8 cm, weighing around 45 gms.
• Formation of nail beds and possible spontaneous fetal movements, though subtle.
• Bone ossification centers begin forming, and sex is discernible.

End of 16th Gestational Week

• Length varies from 10 to 17 cm with a weight between 55 to 120 gms.
• Fetal heart sounds audible with a stethoscope, exhibiting well-formed lanugo.

End of 20th Gestational Week

• Length at approximately 25 cm, weight is around 223 gms.
• Visible spontaneous fetal movements and antibody production capacity.

End of 24th Gestational Week

• Length ranges from 28 to 36 cm, weight about 550 gms.
• Presence of meconium in the intestine and antibody transfer from mother to fetus begins.

End of 28th Gestational Week

• Length between 35 to 38 cm and weight 1200 gms.
• Lung development progresses with maturity of alveoli, and descent of testes begins.

End of 32nd Gestational Week

• Length measures 38 to 43 cm, weight around 1600 gms.
• Fetus demonstrates responsive movements to external sounds and may assume birth position.

End of 36th Gestational Week

• Length ranges from 42 to 48 cm and weight between 1800 to 2700 gms.
• Development of subcutaneous fat and distinctive sleeping/activity patterns.

End of 40th Gestational Week

• Length of 48 to 52 cm with a birth weight of approximately 3000gms (7 to 7.5 lbs).
• Notable fetal movements and reactions to light and sound; increased availability of vernix caseosa.

Measurement Units

• Pregnancy duration may be tracked in lunar months (4 weeks) or by trimester (3 months).
• Total pregnancy is typically 10 lunar months (40 weeks), with fetal development occurring over 9.5 lunar months or 3 full trimesters (38 weeks or 266 days).

Explore the infundibulum, the distal part of the fallopian tube, shaped like a funnel and crucial during ovulation. This quiz covers its functions, structure, and significance in ovum production and transport. Test your knowledge of this essential anatomy!