Anyone Who Had A Heart:
A Case Study in Physiology

by
Phil Stephens
Biology Department
Villanova University, Villanova, PA


Part I—Prenatal Visit

It had been a hectic day for the doctor, and his last patient was on time for her appointment.

“Hi. Sis.”

“Hi, Jim. How’s my kid brother?”

“Tired—how’s the first-time mom? Have you stopped work yet?”

“Come on, Jim, I’m a career woman. The chemical industry needs me. It’s tough to go cold turkey. When Dave and I decided to have a family, we agreed that I should work as long as I could.”

“You’re the size of a house, Jen. You’re 37 years old, you have twins that are 28 weeks, and I really would like you to carry them as long as you can.”

“Oh, oh, here comes the lecture again. I know you didn’t like the fertility procedure we did, but I just couldn’t get pregnant. Anyway, as you so tactfully pointed out, doctor, I am not getting any younger. Look at it this way; we’re having our family all at once.”

There was a knock at the door and the nurse entered.

“How did the ultrasound go?”

“It’s like Times Square,” replied the nurse. “Arms and legs everywhere—it’s almost impossible to see anything, and those kids are so active. I just hope they slow down after they’re born, otherwise you’ll get no rest until they go to college. It’s crazy in there, with two hearts beating. And with yours in the background, it’s tough to isolate one. As best as I can tell, the rates are around 130 to 160 beats a minute.”

“OK, well let’s see if the expert can hear anything.”

Both women glared at the doctor.

“Do you need the crane or can you get up on the table by yourself?”

Jen looked at the nurse and said, “Is he like to this to all his patients?”

“No comment; I need this job.”

They laughed and Jim went to work. Moving the head of his stethoscope to different locations, he tried to isolate the sounds from one heart. His expression changed as he listened intently. Jen began to worry as her brother took longer than usual with his stethoscope.

“Is everything OK?” she asked.

Jim looked concerned. He was reluctant to tell his sister that he thought he had heard a heart murmur. Like his nurse had said, it was difficult to hear just one heart. He didn’t want to alarm his sister, so he made a joke of the situation.

“Must be a girl in there, she won’t stop talking. I think she said something about not leaving the hospital in just any outfit.”

Jen went to hit her brother, but he easily evaded the playful smack.

“It’s tough to predict when the babies will arrive, so I think you should start coming to see me every week, Jen.”

“Is there a problem? You did all of the tests, and you said that I’m not diabetic. The alpha-fetoprotein levels indicate no neural tube defects, and that horrible amniocentesis procedure showed no birth defects or Rhesus problems.”

“It’s OK, Sis. It’s quite normal for women who are close to delivery to visit their OB-GYN every week. It’s tough to predict delivery with multiple births, because they rarely go full term. So, to be on the safe side, let’s get together every week from now on. In that way I can see your lovely smiling face more often.”

Jen scowled at her brother.

“For once in your life, do what I ask,” Jim said. “And bring Dave with you next time.”

A little later, as Jim was finishing his paper work for the day, the nurse returned to his office.

“Everything OK with Jen?”

“I can’t stop thinking about that vague sound I heard. It sounded like a heart murmur, but it’s so tough to single out with two kids in there.”

“I thought I heard it too. The babies seem active and are about the same size. No history of birth heart defects in either family, but I guess you never know with twins in an older mom.”

“My thoughts exactly. I don’t want to worry her because you know how hyper she can be. I guess we’ll need to keep a close eye on her, and on my nephew and niece.”

“Does Jen know the sexes?”

“She and Dave don’t want to know. They want to be surprised.”

Questions

  1. Draw a diagram of the heart of a human adult. Show the circulation of the blood through the heart and to and from the body and the lungs.
  2. Draw a diagram of the heart of a human fetus. Show the circulation of the blood through the heart and to and from the body and the lungs.
  3. What are the major structural differences between the fetal and the adult human heart? Draw and label these differences on your diagram of the fetal heart. How do these structures alter the circulation of blood?
  4. Why is the pulmonary circulation reduced in the human fetus?
  5. Are heart rates of 130 to 160 normal in a human fetus?

Go to Part II—“The Arrival”

Date Posted: 12/04/04 nas

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