The urethra travels through the corpus spongiosum, one of three cavernous bodies in the human penis. The other two cavernous bodies are a set of sponge-like erectile tissues called the corpus cavernosum. The vas deferens and epididymis are both part of the storage and transportation of semen. The vas deferens joins with the urethra in the penis to facilitate ejaculation.

The pudendal nerve transmits sensation from the external genitalia, the skin around the anus, and the perineum. It also provides motor function to several important structures in the area, including musculature of the pelvic floor, the external urethral sphincter, and the external anal sphincter. The other nerves listed do not provide any sensory or motor innervation to the genitals. 

Sperm development begins with spermatogonia, undifferentiated male germ cell of the seminiferous tubules. During spermatogenesis, these cells first divide via mitosis to form two primary spermatocytes. Those cells then divide meiotically to form two secondary spermatocytes, which then undergo meiosis II to become spermatids. Spermatids then mature further to form spermatozoa via the process of spermiogenesis.  

The process by which spermatids mature into motile spermatozoa is called spermiogenesis. It is the final stage of spermatogenesis. During spermiogenesis, a polarity develops within the cell, which defines the cell as having a head end and a tail end. An acrosmal cap is formed over the head of the sperm, and a tail is formed via the elongation of a centriole within the cell. 

The cap that forms over the head and anterior tail of the spermatozoa is known as the acrosome. It is derived from the golgi apparatus, an organelle within the sperm cell. The acrosome prevents premature fertilization of the egg outside of the uterus. Within the uterus there are several proteolytic and glycosidic enzymes that begin to break down the acrosome, rendering it capable of fertilization. When the sperm meets the egg, the acrosome is then able to bind to the egg's zona pellucida, which triggers further breakdown of the acrosome (known as the acrosome reaction). This further breakdown releases enzymes held within the acrosome that allow the sperm to penetrate the zona pellucida, allowing conception to occur. 

A fetus that assumes a "head down" position during labor is said to have a cephalic presentation. The infant may still be oriented in a number of directions, such as vertex position, with the occiput anterior and the face and front of the body toward the mother's spine, face presentation with the head tilted back into full neck extension, or occpito-posterior, in which the occiput is against the sacrum. In a transverse presentation, the fetus is sidelong, while a breech presentation the fetus' head is superior while the legs are inferior.

The designations for parity are as follows:

• Nulliparous: Never delivered a child or carried a pregnancy past 20 weeks
• Primiparous: Has given birth once or is about to give birth for the first time
• Multiparous: Has given birth twice
• Grand multiparous: Has given birth three or more times

Contractions in labor are stimulated by oxytocin, a nonapeptide hormone produced in the hypothalamus and stored in the posterior pituitary. Oxytocin also triggers postpartum contractions in order to compress the lax uterine wall and reduce postpartum bleeding. Prolactin is a hormone essential to breast-milk production, while estrogen and progesterone have a multitude of roles in both fetal and placental development.  

Oxytocin, a nonapeptide hormone produced in the hypothalamus, has a variety of physiological roles. It increases trust, generosity, and other markers of social cohesion. In intimate relationships, it increases feelings of affection, love, sexual arousal, and contentment. It is an important hormone in labor, as it triggers contractions both during labor and postpartum in order to reduce bleeding and uterine size after delivery. It also acts as an immune modulator in wound healing. It does not, however, increase appetite - studies have shown it to have the opposite effect, acting as an appetite suppressant in human and animal models. 

During the later stages of labor, the cervix, normally a four centimeter-long muscular sphincter, releases its mucus plug, then thins and shortens. The release of the mucus plug is termed the "bloody-show," and the thinning and shortening of the cervix is called effacement. Cervical effacement is almost always accompanied by cervical dilation, or a widening of the os in order to allow passage of the fetus. This all happens in the transition phase of labor.