Anatomy of the male reproductive system | Reproductive system physiology | NCLEX-RN | Khan Academy

Summary

This educational script explores the male reproductive system, focusing on its key components and functions. It introduces anterior and posterior views, then dives into the sagittal view, highlighting the internal organs. The testes, responsible for sperm production and testosterone, are detailed alongside the scrotum's role in temperature regulation. The script also covers the epididymis, vas deferens, and accessory glands, explaining their contributions to sperm's journey and function. Finally, it touches on the seminal vesicles, prostate gland, and bulbourethral glands, emphasizing their role in semen composition and sperm mobility.

Takeaways

• 🔍 The male reproductive system can be viewed from two perspectives: anterior (front) and posterior (back) views.
• 📐 A sagittal view is a side view that involves a vertical cut through the middle of the body, showing the internal structure on one side.
• 🌡 The testes are the key organs for sperm production and must be kept at a lower temperature than the body for proper spermatogenesis.
• 💼 The scrotum is the sac that holds the testes and helps regulate their temperature through the action of the cremaster and dartos muscles.
• 🏃‍♂️ The cremasteric reflex is an involuntary response where the cremaster muscle contracts, pulling the testes upward when the thigh is lightly brushed.
• 🤺 Testosterone, produced in the testes, is responsible for secondary sexual characteristics such as body and facial hair growth, muscle development, and voice deepening.
• 🛤️ The epididymis is a series of tubes where sperm mature and gain energy through additional mitochondria and develop flagella for propulsion.
• 🚰 The vas deferens is the duct that transports mature sperm from the epididymis to the urethra, running within the spermatic cord alongside blood vessels.
• 💧 Seminal vesicles contribute the majority of semen volume, providing an alkaline fluid rich in fructose to nourish sperm during their journey.
• 🚿 The prostate gland and bulbourethral glands add fluid to semen, enhancing sperm mobility in the vagina and providing lubrication.
• 📍 The urethra is the tube through which semen travels to exit the body, passing through the penis, which plays a crucial role in depositing sperm inside the vagina during reproduction.

Q & A

What are the two main views used to examine the male reproductive system?

The two main views used to examine the male reproductive system are the anterior view, which is a front view, and the posterior view, which is a back view. Additionally, the sagittal view, which is a vertical cut through the middle of the body, is also important.

What is the primary function of the testes in the male reproductive system?

The primary function of the testes is spermatogenesis, which is the production of sperm, the male reproductive cells, and the production of the male hormone testosterone.

Why is the temperature inside the scrotum important for sperm production?

The temperature inside the scrotum is important for sperm production because it needs to be slightly lower than the core body temperature to facilitate the process of spermatogenesis.

What is the cremasteric reflex, and what causes it?

The cremasteric reflex is an involuntary contraction of the cremaster muscle that pulls the testes slightly upward when the upper and inner part of the thigh is lightly brushed. It is a protective reflex to prevent injury.

What role does the epididymis play in the male reproductive system?

The epididymis provides a place for sperm to mature and develop before they embark on their journey. It is a long, convoluted set of tubes where sperm gain more mitochondria and develop flagella for propulsion.

What is the function of the vas deferens in the male reproductive system?

The vas deferens is a tube that transports mature sperm from the epididymis to the urethra, which is the next part of the reproductive tract leading to the outside of the body.

What are the accessory glands of the male reproductive system, and what do they contribute to the sperm's journey?

The accessory glands include the seminal vesicles, prostate gland, and bulbourethral glands. They provide fluids that nourish and protect the sperm, enhance its mobility, and provide energy for its journey.

How does the fluid from the seminal vesicles benefit the sperm?

The fluid from the seminal vesicles is alkaline, which helps neutralize the acidic environment of the urethra and vagina, and it is rich in fructose, providing a sugar source for the mitochondria to produce ATP, the energy currency for sperm.

What is the role of the prostate gland in the male reproductive system?

The prostate gland produces prostatic fluid that contributes to the semen's volume and increases the mobility of sperm once it reaches the vagina.

What is the function of the bulbourethral glands in the male reproductive system?

The bulbourethral glands produce a thick lubricant that facilitates the passage of semen through the urethra and provides lubrication for the vagina during sexual intercourse.

How does the urethra play a role in the reproductive process?

The urethra serves as a channel through which semen travels from the reproductive system to the outside of the body, facilitating the deposition of sperm during sexual intercourse.

Outlines

00:00

🔍 Exploring the Male Reproductive System Views

This paragraph introduces the male reproductive system, emphasizing the importance of understanding it from two distinct perspectives: anterior and posterior views for a comprehensive understanding. It then explains the concept of a sagittal view, which involves a vertical cut through the body to observe internal structures. The paragraph also mentions that most of the male reproductive organs are internal and not visible externally, with the exception of the penis and scrotum, setting the stage for a deeper dive into the organs' functions.

05:03

🌡️ The Testes: Sperm Production and Temperature Regulation

The second paragraph delves into the function of the testes, the primary organs in the male reproductive system, where spermatogenesis, the creation of sperm, takes place. It explains the necessity of a cooler temperature for sperm production, which is facilitated by the scrotum's ability to regulate temperature through the cremaster and dartos muscles. The paragraph also touches on the cremasteric reflex, a protective response to stimuli, and the production of testosterone, which is responsible for secondary sexual characteristics such as body hair growth, muscle development, and voice deepening.

Keywords

💡Anterior view

An anterior view is a perspective that looks at something from the front. In the context of the male reproductive system, the script describes it as the first point of view, where everything is visualized from the front side, providing an initial understanding of the system's layout.

💡Posterior view

A posterior view is the opposite of an anterior view, looking at something from behind. The script contrasts this with the anterior view, indicating that there are two primary perspectives from which to understand the male reproductive system.

💡Sagittal view

A sagittal view is a type of perspective that involves a vertical cut through the middle of an object, revealing its internal structure. The script uses this term to describe the second point of view, where the male reproductive system is viewed as if cutting through the middle to observe the internal organs.

💡Testes

The testes are the male reproductive organs responsible for the production of sperm and the hormone testosterone. The script highlights their importance as the key organ in the male reproductive system and explains their function in spermatogenesis and hormone production.

💡Spermatogenesis

Spermatogenesis is the process of sperm production within the testes. The script describes this process as the creation of sperm, which is essential for male fertility and the male contribution to reproduction.

💡Scrotum

The scrotum is a sac-like structure that houses the testes outside the body. The script explains its role in temperature regulation for the testes, which is crucial for sperm production, by retracting or descending to adjust the temperature.

💡Epididymis

The epididymis is a series of coiled tubes that sit atop the testes. The script describes its function as a place for sperm to mature and develop before they embark on their journey, gaining mitochondria and flagella in preparation.

💡Vas deferens

The vas deferens is a duct that transports sperm from the epididymis to the urethra. The script explains its role in the male reproductive system as the conduit through which sperm travels, highlighting its position within the spermatic cord.

💡Spermatic cord

The spermatic cord is a bundle that contains the vas deferens, along with arteries and veins that serve the testes. The script mentions this structure as a critical component that supports the transport of sperm and nutrients to the testes.

💡Accessory glands

Accessory glands are glands that contribute to the production of semen by providing fluids that support sperm. The script identifies the seminal vesicles, prostate gland, and bulbourethral glands as accessory glands, each with a specific role in supplying nutrients, enhancing mobility, and lubrication for sperm.

💡Semen

Semen is the fluid mixture that contains sperm and is ejaculated from the male during sexual activity. The script differentiates semen from sperm, noting that semen is composed of sperm plus the fluids from the accessory glands, which are essential for sperm survival and mobility.

💡Urethra

The urethra is a tube that carries semen and urine from the body. In the context of the male reproductive system, the script describes the urethra as the pathway through which semen travels to be expelled from the body during ejaculation.

💡Penis

The penis is the male organ used for sexual intercourse and the expulsion of semen. The script explains its role in reproduction as the organ that penetrates the vagina to deposit sperm inside the female reproductive system.

Highlights

Introduction to the male reproductive system from two different viewpoints: anterior and posterior.

Explanation of the anterior view, focusing on the front aspect of the male reproductive system.

Clarification of the posterior view, which examines the system from behind.

Introduction of the sagittal view, emphasizing the lateral perspective by cutting through the middle.

Description of the organs visible externally: the penis and the scrotum containing the testes.

Discussion on the importance of the testes as the key organ for sperm production and testosterone generation.

Explanation of spermatogenesis, the process of sperm creation within the testes.

Details on the necessity of a cooler temperature for sperm production, facilitated by the scrotum.

Functioning of the cremaster and dartos muscles in temperature regulation for the testes.

The cremasteric reflex, an involuntary response to stimulation of the inner thigh.

Role of testosterone in developing secondary sexual characteristics such as body hair growth.

Introduction to the epididymis as a site for sperm development and storage.

The process of sperm gaining mitochondria and flagella for energy and propulsion in the epididymis.

The vas deferens' role in transporting sperm from the epididymis to the urethra.

Overview of the spermatic cord containing the vas deferens, artery, and vein for the testes.

Importance of accessory glands in providing fluids and nutrients for sperm during their journey.

Function of the seminal vesicles in producing alkaline fluid rich in fructose for sperm energy.

Role of the prostate gland in enhancing sperm mobility within the female reproductive system.

Contribution of the bulbourethral glands in producing a lubricant for the urethra and vagina.

The urethra's role in transporting semen, a mixture of sperm and glandular fluids, out of the body.

The function of the penis in reproduction, specifically in penetrating the vagina for sperm deposition.

Transcripts

- So let's look at the male reproductive system.

And so when we learn about the male reproductive system

it's useful to actually look at it

from two different points of view

and so the first view we'll take a look at

is called an anterior view.

And what that is is basically we take

everything in this box here

and so what we'll do is --

it's a little bit tough to see there.

This is zoomed out.

So we'll blow it up for you

and that's basically what you see there.

And so that's called an anterior view.

Looking at it from the front.

And that's sort of the opposite to a posterior view

which is looking at it from behind.

That would be a posterior view.

And so there's two points of views like I mentioned.

So the other one is called the sagittal view

and what a sagittal view is

is let's look at this guy over here.

Let's say that this is his left side

because this is where his left hand is

and this is his right side.

And so in a sagittal view what you do is you

sort of make a cut right down the middle here

and you sort of cut away everything on one side.

So in this case

it would be the left side that we're cutting away

because what we want to do

and I'll draw the --

I'll draw a little eye here.

What we want to do is look toward the right side

toward what's remaining on the right side.

So we're seeing this cut surface here.

And so what that ends up looking like

is something like this here

and so this is called a sagittal view

and to reorient you

this here in the background this is the right leg

because remember we're looking --

we're looking this way

so this ends up being the right leg.

So those are the two views that are important

when we're learning about the male reproductive system.

And actually it's also important to mention that

most of what you see here

is actually contained within the body

so you don't actually see that

when you look from the outside.

What you do see is just the penis

and the scrotum that contains the testes

and we'll come to what all of that is soon.

Now that we've taken a look at the two different views

let's clear away some of this stuff

and meet the organs.

So the first set of organs we'll look at

they're actually paired organs.

They're the testes

and they're sort of the key organ

in the male reproductive system.

I'll just shade them in for you here.

And the testes are pretty interesting.

What happens in the testes

is the process of spermatogenesis

and so what spermatogenesis is

is the creation of sperm

and sperm are the male contribution to a baby.

So sperm production in the testes

has to happen at a certain temperature.

It has to be at a temperature that's a bit lower

i.e., a bit colder that core body temperature

which is pretty warm.

And so the testes have to be kept at a temperature

that's a little bit lower than body temperature

and they do that by hanging out in this --

this fleshy sac outside of the body

called the scrotum.

And so I'm just pointing at it now.

And so this is called the scrotum

and the way that the scrotum regulates

the temperature of the testes

is by sort of retracting upward toward the body

if it gets a little bit cold

so that they can stay a bit warmer closer to the body

or by descending a little bit if it gets a little bit warm

and so it does that --

the retracting upward and the descending via two muscles.

The first one is called the cremaster muscle --

cremaster --

and the second one is called the dartos muscle.

Kind of a cool name.

And so those two muscles

help to regulate the temperature of the testes

so that sperm can be produced.

And interestingly there's something called

the cremasteric reflex

where if you sort of lightly brush on the --

on the upper and inner part of the thigh here on a male

instinctively or reflexively rather

the cremaster muscle will contract

and pull the testes slightly upward on that side.

And that's called the cremasteric reflex.

Now the testes also have another really important function

besides producing sperm

and that's the creation of the major male hormone

called testosterone.

And the testosterone that you produce in your testes

is actually responsible for

all of your secondary sexual characteristics

and when I say secondary sexual characteristics

I mean things like hair growth.

So when you hit puberty around 12 or 13 years old

and you start to produce testosterone in greater amounts

you sort of get an outbreak of body hair.

So you get hair on your knuckles

and on your arms and on your legs and your face

and you'll start to grow pubic hair

and so testosterone is the main driver of that hair growth.

In addition to that

you get sort of muscle growth

and you also get a deepening of your voice.

And so next up what we have is the epididymis

and so I'll just color those in.

Those sit right on top of the testes on either side.

And so the role of the epididymis

is to sort of provide a place for the sperm

to sort of hang out and develop

and so the epididymis is this really long

convoluted really wavy set of tubes

that sperm sort of spends a lot of time in

before it goes off on its journey.

And so if you were going off on a journey

you'd sort of pack a few things in preparation

and sperm sort of do the same thing.

And so when the sperm are hanging out in the epididymis

they gain more mitochondria,

the organelle in the cell

that provides the cell with energy.

And so the sperm are about to embark on this huge journey

and they have to be ready at basically a moment's notice

to sort of shoot out and swim a long way

and they're going to need mitochondria

because they're going to need a lot of energy.

In the epididymis they also develop

really long tails called flagella

and that sort of helps to propel them

on their journey as well.

And so from the epididymis

sperm sort of drains out of the epididymis

and into this tube called the vas deferens

and so the vas deferens actually

drains the epididymis of sperm

and brings the sperm upwards behind the bladder

and into the urethra

which is the next part of the reproductive tract.

Now the vas deferens actually runs within a bundle

called the spermatic cord

and inside the spermatic cord

you actually have an artery that serves the testes

and you also have a vein that serves the testes.

And so all of that together --

and you have that on either side

that's called the spermatic cord

and let me just draw one on this side as well.

So there's your artery

and you've got your vein as well.

So before we move on

let's just clear off a few things

or everything, that's fine too

and next we'll talk about the accessory glands.

And so what the accessory glands do

is basically provide sperm

with things that they need along their journey.

And so if you were going on a journey

you might make a few pit stops at a few shops

and pick up some things

and that's basically what's happening with sperm.

And so I'll point out some accessory glands here

but before I do that

I'll just orient you to where they are

with respect to the bladder.

And so this yellow object here is the bladder

and you can see it on the sagittal view here.

And so the first accessory gland that we're going to mention

is called the seminal vesicle

and there are actually two of them

and I'll shade it in here.

So on the sagittal view

you can see it behind the bladder quite nicely

and on the anterior view

you have to sort of imagine

that it's behind the bladder in there

and about there.

And so those are the seminal vesicles.

And what they do

their contribution to sperm is a lot of fluid

and in fact they actually make up 60% of semen volume

and just to hammer out some terminology here

semen is different from sperm

in that semen equals sperm

plus the fluid that it picks up

on the way from the accessory glands.

And so the fluid that the sperm pick up

from the seminal vesicles

is actually somewhat alkaline.

And that's to neutralize

the somewhat acidic environments

of the male's own urethra

and the vagina where the sperm will end up

and to be alkaline

that just means that your pH is greater than 7

which is what water is.

The fluid is also rich in fructose

and that's so that the mitochondria have sugar

that they can use to produce ATP

and ATP is what the sperm use for energy

to complete their long journey.

Now the other two accessory glands are called

the prostate gland and the bulbourethral glands

and there are actually two bulbourethral glands,

one on either side of the penis.

These three glands actually

contribute more fluid to semen.

The prostate gland actually makes prostatic fluid

and that increases the mobility of sperm

once it reaches inside the vagina

and the bulbourethral gland

sort of just makes a thick lubricant

for both the urethra and the vagina.

Now semen actually travels

through a tube called the urethra

which you can see here in red

to get to the outside of the body

and it travels through the urethra

through the penis which is here in purple blue

and so in reproduction the role of the penis

is to actually penetrate the vagina

so that sperm can be deposited inside.