Pelvis Anatomy Overview

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Questions and Answers

What structure is referred to as the entrance to the true pelvis?

Pelvic cavity

Pelvic outlet

Symphysis pubis

Pelvic inlet (correct)

During what time frame must fertilization occur after ovulation for successful conception?

48 to 72 hours

24 to 48 hours (correct)

72 to 96 hours

12 to 36 hours

Which part of the pelvis supports the uterus during the later months of pregnancy?

Coccyx

Pelvic cavity

False pelvis (correct)

True pelvis

What is the structure composed of 5 fused bones located below the sacrum?

Coccyx Signup and view all the answers

What happens to the ovum if fertilization does not occur within 24 hours?

It atrophies and becomes nonfunctional Signup and view all the answers

What is the term for the fusion of the chromosomal material of the ovum and spermatozoon?

Zygote Signup and view all the answers

Which chromosome combination results in a female child?

XX Signup and view all the answers

What aids in slowing and controlling the speed of birth within the pelvic cavity?

Pelvic cavity's curve Signup and view all the answers

What must occur for fertilization to be successful?

Equal maturation of both sperm and ovum Signup and view all the answers

Which anatomical structure directs the fetus into the true pelvis for childbirth?

False pelvis Signup and view all the answers

What hormone is secreted by the trophoblast cells to maintain the corpus luteum after fertilization?

Human chorionic gonadotrophin (hCG) Signup and view all the answers

Which structure is referred to as the decidua after fertilization?

Uterine endometrium Signup and view all the answers

What is the primary function of the decidua during early pregnancy?

To act as a barrier against infections Signup and view all the answers

Which hormone is associated with the preparation of the uterine lining for implantation?

Progesterone Signup and view all the answers

At what stage does the decidua start to disappear during pregnancy?

20th to 24th week Signup and view all the answers

Which infectious organism is mentioned as being protected against by the decidua?

Spirochete of syphilis Signup and view all the answers

What is one significant change in the uterine endometrium after fertilization?

It continues to grow in thickness and vascularity. Signup and view all the answers

What does the term 'decidua' refer to in the context of pregnancy?

The part of the endometrium that is discarded after birth Signup and view all the answers

What structure differentiates into the central nervous system?

Neural tube Signup and view all the answers

At what week of intrauterine life can brain waves be detected on an electroencephalogram (EEG)?

8th week Signup and view all the answers

What forms as a result of the diaphragm not completely dividing the thoracic cavity from the abdomen?

Hernia Signup and view all the answers

Which of the following components forms surfactant in the alveoli?

Phospholipid Signup and view all the answers

What important development in the respiratory system occurs between the 24th and 28th weeks of pregnancy?

Development of alveoli and capillaries Signup and view all the answers

What role do fetal adrenal glands play in intrauterine life?

Synthesize estrogen precursors Signup and view all the answers

What is the condition called when the intestines coil and remain outside the abdomen?

Omphalocele Signup and view all the answers

What substance is relevant to meconium formation in the intestines during pregnancy?

Bile Signup and view all the answers

During which week does the digestive tract separate from the respiratory tract?

4th week Signup and view all the answers

What is a key characteristic of the GI tract before birth?

It is sterile. Signup and view all the answers

What developmental issue may result from failure of the intestines to rotate 180 degrees?

Volvulus of the intestine Signup and view all the answers

What structure appears black or dark green and is a collection of cellular waste in the intestines?

Meconium Signup and view all the answers

When do testes typically descend into the scrotal sac during gestation?

34th - 38th week Signup and view all the answers

Which hormone is primarily produced by the syncytial cells of the placenta?

Estriol Signup and view all the answers

What is a major function of Braxton Hicks contractions?

To maintain vascular pressure in the intervillous spaces Signup and view all the answers

What position provides the most efficient uterine perfusion during pregnancy?

On the left side Signup and view all the answers

What is progesterone's primary role during pregnancy?

Maintain endometrial lining Signup and view all the answers

What complication may arise when a pregnant woman lies flat on her back?

Supine hypotension Signup and view all the answers

What weight range does the placenta typically reach by term?

400-600 gms Signup and view all the answers

Which of the following is NOT a function of progesterone?

Stimulate placental growth Signup and view all the answers

Which ions may change during pregnancy, potentially affecting uterine contractility?

Potassium and Calcium Signup and view all the answers

What is the effect of a smaller placenta on fetal circulation?

Suggests inadequate circulation to the fetus Signup and view all the answers

What causes the reduction in uterine contraction potential during pregnancy?

Change in electrolyte levels Signup and view all the answers

What is the primary function of the umbilical cord?

To transport oxygen and nutrients to the fetus Signup and view all the answers

What percentage of infants are born with a single artery and vein in the umbilical cord?

1% Signup and view all the answers

What is Wharton's jelly's primary role in the umbilical cord?

Giving the cord bulk and support Signup and view all the answers

Which of the following describes amniotic fluid at term?

800 – 1,200 mL Signup and view all the answers

What happens to the umbilical arteries after birth?

Their smooth muscles constrict to help prevent hemorrhage Signup and view all the answers

What is a common consequence of oligohydramnios?

Reduced fetal movement Signup and view all the answers

How does the fetus primarily absorb amniotic fluid?

By swallowing it Signup and view all the answers

What occurs in the case of hydramnios during pregnancy?

Excessive fluid accumulates in the amniotic sac Signup and view all the answers

How long is the umbilical cord typically at term?

53 cm (21 inches) Signup and view all the answers

What happens to the chorionic villi that are not involved in implantation?

They gradually thin and become smooth chorion Signup and view all the answers

What is the primary component of the umbilical cord that contributes to its structure?

Wharton's jelly Signup and view all the answers

Which condition can lead to excessive amniotic fluid production?

Esophageal atresia Signup and view all the answers

What does the term 'nuchal cord' refer to?

A loose loop of the cord around the neck Signup and view all the answers

During what period can hCG be detected in maternal blood and urine?

Within the first month of pregnancy Signup and view all the answers

Study Notes

Pelvis and Innominate Bones

The innominate bones consist of three divisions: Pubis (anterior), Ilum, and Ischium.
The pubis forms the symphysis pubis, the junction of the innominate bones at the front of the pelvis.
Sacrum is located above the coccyx and forms the upper part of the pelvic ring.
Coccyx is comprised of five small, fused bones, allowing some movement during childbirth to accommodate the fetal head.

Obstetric Division of the Pelvis

False pelvis: The superior half that supports the uterus and aids in fetal descent.
True pelvis: The inferior half, crucial for childbirth.
Pelvic inlet: Heart-shaped entrance to the true pelvis where the fetus passes during vaginal birth.
Pelvic outlet: Bounded by the ischial tuberosities, symphysis pubis, and coccyx, marking the exit for the fetus.
Pelvic cavity: Curved space between the inlet and outlet that regulates the speed of birth, affects fetal chest compression, and promotes lung fluid expulsion.

Fertilization

Fertilization, also known as conception or fecundation, is the union of an ovum and spermatozoon, typically occurring in the fallopian tube.
Only one ovum matures and becomes capable of fertilization for about 24 to 48 hours post-ovulation.
Sperm can survive in the female body for approximately 48 to 72 hours.
Successful fertilization depends on sperm maturity, ability to reach the ovum, and penetration capability.

Zygote Formation

Upon penetration, the sperm and ovum chromosomes fuse to create a zygote with 46 chromosomes (23 pairs).
A fertilized ovum from an X-carrying sperm results in female offspring (XX); Y-carrying sperm results in male offspring (XY).

Decidua

After fertilization, the corpus luteum remains active, producing hormones like hCG, necessary for maintaining the uterine lining.
The decidua is the thickened uterine endometrium during pregnancy, which is categorized into three areas.
Braxton Hicks contractions occur from about 12 weeks, maintaining pressure in uterine blood spaces.

The Placenta

A vital organ, weighing 400-600 g at term, serving as a site for maternal-fetal exchange.
Primarily produces hormones like estrogen, progesterone, and hCG to support pregnancy.
Estrogen aids mammary gland development; progesterone maintains the endometrial lining and decreases uterine contractions.

Umbilical Cord

Formed from fetal membranes, the umbilical cord connects the embryo to the placenta, typically measuring about 53 cm long at term.
Contains one vein (carrying oxygenated blood to the fetus) and two arteries (returning deoxygenated blood to the placenta).
Wharton’s jelly protects the cord from pressure and prevents vascular obstruction.
The cord is assessed at delivery for the number of arteries and veins to detect potential anomalies.

Amniotic Fluid

Produced by the amniotic membrane, the quantity ranges from 800 to 1,200 mL at term, with functions including protection and cushioning for the fetus.
Inadequate swallowing due to conditions like esophageal atresia can lead to hydramnios (excess fluid) or oligohydramnios (insufficient fluid).
The fluid is reabsorbed continually, promoting fetal lung development and protein exchange, while offering a protective environment.

Amniotic Membranes

The outermost layer forms chorionic membranes, providing support to the amniotic sac.
These membranes have no nerve supply, allowing for painless rupture during labor.

Labor and Delivery

For successful vaginal delivery, the fetus transitions through the pelvic inlet, cavity, and outlet.
Proper positioning of the mother during labor ensures optimal placental blood flow and minimizes complications.### Respiratory System Development
Neural tube differentiates into the central nervous system and neural crest for the peripheral nervous system.
At 3 weeks, respiratory and digestive tracts begin as a single solid tube that later canalizes.
By the end of the 4th week, a septum separates the esophagus and trachea; lung buds emerge.
By 7 weeks, diaphragm development is incomplete; potential for diaphragmatic hernia if it doesn’t close properly.
Key milestones in respiratory development include:
- Alveoli and capillaries form between 24-28 weeks; essential for gas exchange.
- Spontaneous respiratory movements start at 3 months and continue throughout pregnancy.
- Lung fluid with low viscosity and surface tension forms to assist in alveolar expansion.
- Surfactant is secreted by alveolar cells around 24 weeks, reducing surface tension and preventing collapse.

Endocrine System Function

Endocrine organs begin to function when mature, impacting crucial processes:
- Fetal adrenal glands provide precursors for estrogen synthesis by the placenta.
- Fetal pancreas produces insulin essential for fetal metabolism.
- Thyroid and parathyroid glands are vital for metabolic functions and calcium balance.

Digestive System Development

At 4 weeks, the digestive tract separates from the respiratory tract and starts as a solid structure, hollowing out later.
By 6 weeks, as the abdomen shrinks, portions of the intestine are pushed into the umbilical cord area until the 10th week.
Proper rotation of the intestine upon re-entering abdominal cavity prevents complications:
- Innadequate rotation can cause volvulus, leading to intestinal obstruction.
- Omphalocele and gastroschisis are congenital anomalies involving intestinal positioning.
Meconium, a mix of waste materials, begins forming by the 16th week, indicating proper gastrointestinal function.

Nervous System Development

Nervous system formation occurs actively between the 3rd and 4th weeks.
High glucose consumption during this phase leaves the mother with mild hypoglycemia, causing symptoms like dizziness.
Testes develop in the abdominal cavity, with descent into the scrotal sac typically occurring between 34-38 weeks, crucial for male infants’ health.

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Description

This quiz covers the anatomy of the pelvis, including the three divisions of the innominate bones: the pubis, sacrum, and coccyx. It provides key details about their locations and functions, particularly during childbirth. Test your knowledge on these essential structures of the pelvic region.