Skip to main content
Search

The reproductive system: fertilisation, pregnancy, parturition and birth

Published on April 30, 2024   28 min

A selection of talks on Reproduction & Development

Please wait while the transcript is being prepared...
0:00
Hello, my name is Dr. Victoria Garside. And I am an ARC DECRA Fellow in the Department of Anatomy and Physiology at the University of Melbourne in Parkville, Victoria, Australia. Today I will be presenting to you the reproductive system, fertilization, pregnancy, parturition, and birth.
0:21
The process of procreation in land vertebrates requires interactive behaviors and specialized genitalia in the male and female for fertilization. Which is the meeting of the sperm and an egg to occur. As a very broad overview, in humans, the reproductive organs or specialized genitalia in the female are the vagina: which is the receptacle for the male organ, the uterus: which is required for fetal development, and the ovaries containing the unfertilized egg. In the male, the reproductive organs are the penis: the organ responsible for the deposition of sperm into the female via the vagina, and the tests: which house the sperm.
1:01
The process of procreation in humans requires specialized interactive behaviors. Coitus, the human sex act has four phases. The first phase is excitement, where erotic stimuli prepare the genitalia for copulation. The second phase is called the plateau phase, and this is where the changes that occur in the excitement phase intensify. The third phase is orgasm, where the changes lead to a climax, causing a series of muscle contractions accompanied by intense pleasure sensations. The final phase is resolution, where the physiological changes return to normal. In humans, the penis in its resting state is flaccid and not able to penetrate the vagina. And therefore requires a specialized sex act called an erection. In an erection, the penis stiffens and enlarges, and releases sperm from the ducts of the reproductive tract during ejaculation. Without this process, fertilization cannot occur. In the excitement phase, males have an erection. And in the female, there's an erection of the clitoris and vaginal lubrication. In both males and females, an erection is a vascular congestion where the arterial blood flow into the spongy erectile tissue exceeds the venous outflow. For the excitement phase, erotic stimuli can be tactile or psychological stimuli. Psychological stimuli can vary drastically between individuals. For tactile stimuli, there are erogenous zones across the body that have receptors that lead to sexual arousal. This includes regions like the genitalia, lips, tongue, nipples, and ear lobes. In the male, the erection reflex begins with tactile stimuli sensed by the mechanoreceptors in the penis or erogenous zone. Sensory neurons signal to the spinal integration center, which inhibits vasoconstrictive sympathetic input on penile arterials. At the same time, nitric oxide produced by the increased parasympathetic input, actively dilates the penile arterials. As the blood flows into the erectile tissue, it compresses the veins and traps the blood, leading to an engorgement of the tissue. The climax of the male sex act coincides with emission. The movement of sperm out of the vas deferens into the urethra. And ejaculation, where the semen is expelled outside the penis with rapid muscle contractions accompanied by intense pleasure sensations and orgasm. This allows sperm to be deposited into the female reproductive tract. The human sex act

Quiz available with full talk access. Request Free Trial or Login.

Show
Hide

The reproductive system: fertilisation, pregnancy, parturition and birth

Embed in course/own notes