Development of the Kidneys | Renal Embryology | Development of the Urinary System | Embryology

Summary

This educational video from Byte Size Med explores the stages of renal development, focusing on the anatomy and structure of the kidneys. It explains the roles of the pronephros, mesonephros, and metanephros in fetal development, detailing how they form and function. The video also covers the ascent of the kidneys from the pelvic region to the abdomen and their blood supply changes. It concludes with the formation of urine and its role in fetal life, encouraging viewers to engage with the content.

Takeaways

• 😀 The human body has two kidneys located in the abdomen, each containing millions of nephrons.
• 🔍 Each kidney is composed of an excretory portion, which includes the nephron components, and a collecting portion, which includes the collecting ducts, calyces, renal pelvis, and ureter.
• 🌱 Kidney development begins with the intermediate mesoderm, which condenses to form nephrogenic cords, leading to the formation of two kidneys bilaterally.
• 🐣 The development of the kidneys occurs in three stages: pronephros, mesonephros, and metanephros, each located at different regions of the embryo.
• 🕒 The pronephros, appearing at week four, is a primitive stage that degenerates and does not function.
• 💧 The mesonephros, which appears late in the fourth week, is functional and performs the filtration work until the metanephros takes over around 12 weeks.
• 🌟 The metanephros, forming by the fifth week, is the final kidney structure that begins to function around the 12th week of gestation.
• 🌿 The ureteric bud from the mesonephric duct induces the formation of the collecting system, including the ureter, calyces, and renal pelvis.
• 🔬 The metanephric blastema differentiates to form the excretory portion of the kidney, including the glomerulus and the renal tubules.
• ⬆️ The kidneys ascend from the pelvic region to the abdominal region as the body grows, and their blood supply transitions from branches of the abdominal aorta to the renal arteries directly.

Q & A

What are the two main functions of the kidneys?

The kidneys have an excretory function, which involves filtering waste and excess substances from the blood to form urine, and a collecting function, which involves transporting urine from the nephrons to the bladder via the ureter.

How many nephrons are present in each kidney and what is their role?

Each kidney has millions of nephrons, which are the functional units of the kidney responsible for filtering the blood, reabsorbing necessary substances, and excreting waste products in the form of urine.

What are the three stages of renal development?

The three stages of renal development are the pronephros, mesonephros, and metanephros. These stages represent the sequential development of the kidney from a primitive to a mature functional organ.

Where is the pronephros located and what is its function?

The pronephros is located in the cervical region of the embryo and is a very primitive structure consisting of cell clusters and tubules. It is non-functional and degenerates early in development.

What is the role of the mesonephros in the development of the kidneys?

The mesonephros, located between the thoracic and lumbar region, is a functional stage that performs filtration and acts as the working kidney until the metanephros takes over. It starts degenerating around the 12th week of development.

How does the metanephros contribute to the formation of the kidney?

The metanephros forms the actual kidney structure. It starts functioning around the 12th week of gestation, taking over from the mesonephros. It includes the formation of the collecting system and the excretory portion of the nephron.

What is the ureteric bud and its significance in kidney development?

The ureteric bud is a growth from the lower portion of the mesonephric duct that forms the collecting system of the kidney, including the calyces, renal pelvis, and ureter.

What is the metanephric blastema and its role in kidney development?

The metanephric blastema is a region of the nephrogenic cord that differentiates to form the excretory portion of the kidney, including the glomerulus and the renal tubules.

How does the interaction between the ureteric bud and the metanephric blastema lead to nephron formation?

The ureteric bud induces differentiation of the metanephric blastema, leading to the formation of the renal vesicle, which then develops into the S-shaped body that forms the glomerulus and the renal tubule, thus completing the formation of a nephron.

What happens to the kidneys' position as the body grows during gestation?

The kidneys initially develop in the pelvic region but ascend to the abdomen as the body grows. This ascent is accompanied by a change in blood supply from branches of the abdominal aorta to the renal arteries directly off the abdominal aorta.

How do the kidneys function during fetal life?

During fetal life, the kidneys form urine that drains into the cloaca and then into the amniotic fluid, playing a crucial role in the development and homeostasis of the fetus.

Outlines

00:00

🧬 Overview of Kidney Development

This paragraph introduces the topic of renal development, focusing on the anatomy and structure of the kidneys. It explains that each of the two kidneys in the abdomen contains millions of nephrons, which are the functional units of the kidney. The nephron's excretory portion includes the glomerulus, proximal convoluted tubule, loop of Henle, and distal convoluted tubule, while the collecting system comprises collecting ducts, minor and major calyces, and the renal pelvis, which connects to the ureter and bladder. The kidneys develop from the intermediate mesoderm, with nephrogenic cords giving rise to the kidneys. The paragraph outlines the three stages of kidney development: pronephros, mesonephros, and metanephros, each located at different regions of the embryo. The pronephros, being the first stage, is non-functional and degenerates, while the mesonephros performs kidney functions temporarily until the metanephros, which forms the actual kidney, takes over around the 12th week of gestation.

05:01

🌱 Detailed Development of Kidney Structures

This paragraph delves into the detailed development of the kidney's structures. It describes the formation of the ureteric bud from the lower portion of the mesonephric duct, which will form the collecting system of the kidney, including the ureter, calyces, and renal pelvis. The metanephric blastema, induced by the ureteric bud, forms the excretory portion of the kidney, starting from the glomerulus to the distal convoluted tubule. The paragraph explains how the ureteric bud induces the differentiation of the metanephric mesenchyme to form renal vesicles, which then develop into S-shaped bodies that become glomeruli and renal tubules. The process of nephron formation is detailed, highlighting the interaction between the ureteric bud and the metanephric blastema. The paragraph concludes with a brief mention of the ascent of the kidneys into the abdominal cavity and the transition of their blood supply from branches of the abdominal aorta to the renal arteries as the body grows.

👶 Fetal Kidney Function and Developmental Stages

The final paragraph summarizes the function of the kidneys during fetal life, where they produce urine that drains into the amniotic fluid via the cloaca. It reiterates the three stages of kidney development: pronephros, mesonephros, and metanephros, emphasizing their sequential roles in the development of the kidney. The paragraph ends with a call to action, encouraging viewers to like and subscribe to the channel for more educational content.

Keywords

💡Nephron

A nephron is the functional unit of the kidney, consisting of a glomerulus, proximal convoluted tubule, loop of Henle, and distal convoluted tubule. In the video, nephrons are central to the discussion of renal development, as they are the structures that the kidneys develop to form, ultimately performing the essential function of filtering blood and producing urine. The script mentions that each kidney has millions of nephrons.

💡Glomerulus

The glomerulus is a network of capillaries located at the beginning of the nephron, where blood filtration begins. It is a crucial part of the nephron's structure and is mentioned in the script as the starting point of the excretory portion of the nephron. The glomerulus is where the initial separation of waste and excess substances from the blood occurs.

💡Loop of Henle

The loop of Henle is a U-shaped tube that extends from the proximal convoluted tubule to the renal pelvis, playing a critical role in the kidney's ability to concentrate urine. In the video, it is described as part of the excretory portion of the nephron, contributing to the kidney's function of regulating water and electrolyte balance in the body.

💡Collecting System

The collecting system refers to the network of ducts and tubules that collect and transport urine from the nephrons to the renal pelvis and then to the ureter. This system includes the collecting ducts, minor and major calyces, and the renal pelvis. The script explains that the collecting system is formed by the ureteric bud, which is a key structure in the development of the metanephros, the final stage of kidney development.

💡Pronephros

The pronephros is the first of the three developmental stages of the kidney, appearing in the cervical region of the embryo. It is a primitive structure that does not function and degenerates early in development. The script describes the pronephros as a precursor to the mesonephros and metanephros, highlighting the sequential nature of kidney development.

💡Mesonephros

The mesonephros is the second stage of kidney development, located between the thoracic and lumbar regions of the embryo. It is a functional structure that performs the initial filtration of blood before the metanephros takes over. In the video, the mesonephros is described as having mesonephric tubules and a duct that opens into the cloaca, showing its transitional role in the development of the kidney.

💡Metanephros

The metanephros is the final and definitive stage of kidney development, forming the actual kidney structure. It begins to function around the 12th week of gestation and takes over from the mesonephros. The script details how the metanephros develops from the ureteric bud and the metanephric blastema, forming both the collecting and excretory portions of the kidney.

💡Ureteric Bud

The ureteric bud is a crucial structure in the development of the metanephros, growing from the lower portion of the mesonephric duct. It forms the collecting system of the kidney, including the renal pelvis, calyces, and ureter. The script explains that the ureteric bud induces the differentiation of the metanephric mesenchyme, leading to the formation of the excretory portion of the nephron.

💡Metanephric Blastema

The metanephric blastema is a region of undifferentiated mesoderm that interacts with the ureteric bud to form the excretory portion of the kidney. It is induced to differentiate by the ureteric bud and gives rise to the structures from the glomerulus to the distal convoluted tubule. The script emphasizes the reciprocal induction between the ureteric bud and the metanephric blastema as a key process in kidney development.

💡Renal Pelvis

The renal pelvis is a funnel-shaped structure that collects urine from the calyces and directs it into the ureter. It is part of the collecting system of the kidney and is formed by the ureteric bud during the development of the metanephros. The script describes how the renal pelvis is connected to the ureter, which in turn empties into the bladder, completing the pathway for urine to leave the body.

Highlights

The kidneys develop from the intermediate mesoderm and the nephrogenic cords are the condensed mesoderm that gives rise to the kidneys.

Kidneys have an excretory portion starting from the glomerulus and a collecting portion including the collecting ducts and tubules.

The collecting system forms minor and major calyces, the renal pelvis, and continues as the ureter to the bladder.

The pronephros is the first stage of renal development, appearing at week four, but it is non-functional and degenerates.

The mesonephros is the second stage, appearing late in the fourth week, and it is functional, performing the work of the kidneys until the metanephros takes over.

The metanephros is the third and final stage of development, forming the actual kidney and starting to function around the 12th week of gestation.

The ureteric bud grows from the lower portion of the mesonephric duct and will form the collecting system of the kidney.

The metanephric blastema induces differentiation to form the excretory portion of the kidney, including the glomerulus and renal tubules.

The ureteric bud and metanephric blastema induce each other's development, leading to the formation of the kidney's collecting and excretory systems.

The number of nephrons in the kidneys increases as gestation continues, eventually reaching millions.

The kidneys initially develop in the pelvic region but ascend to the abdomen due to body growth.

The blood supply to the kidneys changes from branches of the abdominal aorta to directly off the abdominal aorta as they mature.

During fetal life, the kidneys form urine that drains into the cloaca and then into the amniotic fluid.

The renal development stages are pronephros, mesonephros, and metanephros, each with distinct locations and functions.

The pronephros is located in the cervical region, the mesonephros between the thoracic and lumbar region, and the metanephros in the lower lumbar and sacral region.

The metanephric vesicles become S-shaped, with one portion forming the glomerulus and the rest becoming the renal tubule.

The ureteric bud's caudal part forms the ureter, while the cranial part forms the rest of the collecting system.

Transcripts

Hello and welcome to Byte Size Med. In this  

video, we're going to talk about  the stages of renal development.

First let's look at what we need to know in the  anatomy and the structure. So there are two kidneys  

in the abdomen and each kidney has millions of  nephrons. The kidneys have an excretory portion  

and a collecting portion. The excretory portion  of the nephron starts from the glomerulus, then  

the proximal convoluted tubule, the loop of Henle,  and the distal convoluted tubule. The collecting  

system is the collecting ducts and tubules, which  form the minor calyces, then the major calyces,  

the renal pelvis, which continues down as the  ureter, which is going to empty into the bladder.

The kidneys develop from the intermediate  mesoderm and the portions of this mesoderm  

that condense to give rise to the kidneys  are the nephrogenic cords. There are two kidneys,  

so they're bilateral. They extend from the  cervical end to the sacral end of the embryo.  

So if we assume this is the back of the embryo,  it's from the neck end up to the sacral end.  

There are three stages of development. The pronephros,  then the mesonephros, and the metanephros.  

They're one below the other. So the pronephros  is at the cervical region, the mesonephros  

is between the thoracic and the lumbar region  and the metanephros is lower lumbar and sacral.  

The first stage is the pronephros. We're  now at week four. The pronephros is very  

primitive, just some cell clusters and tubules,  and the pronephric duct, this duct opens into  

the cloaca, part of which is going to form the  bladder. But for now it's still the cloaca.  

So the pronephros can't function, it  degenerates. So we're just going to remove that

and now we're on to stage two, the mesonephros.  

This appears late in the fourth week. They have  mesonephric tubules, which are like primitive  

versions of renal tubules, and these are associated  with capillaries. What's that? That's a glomerulus,  

that means they can perform filtration,  and they drain into the mesonephric duct,  

also called the Wolffian duct. Again that opens into  the cloaca. So this stage can perform filtration, so  

it's functional, and it does the work of the  kidneys, until the final kidney takes over.  

So up to around 12 weeks. These tubules, they  start degenerating as well, from the top down.

By the fifth week, the metanephros forms.  Now this is going to form the actual kidney.  

It starts functioning towards the 12th  week, it takes over from the mesonephros.  

From the lower portion of the  mesonephric duct, there's a bud that grows.  

This is the ureteric bud. Now this is going  to form the collecting system of the kidney.  

The lower part of the nephrogenic cord has the  metanephric blastema. The ureteric bud induces  

differentiation of the mesoderm in this region,  and that's going to form the excretory portion.  

First let's look at the ureteric bud. The caudal  part of the bud, that's going to form the ureter.  

So that leaves the cranial part to form the rest.  So it branches and forms those collecting tubules.  

The first few set of branches will form the major  calyces and the next set will form the minor  

calyces. So we're done with the collecting system.  We've got the calyces, the pelvis, and the ureter.  

Now on top of each of these collecting tubules, the  metanephric mesenchyme forms a cap. This is going  

to form the excretory portion of the kidney. The  ureteric bud induces differentiation of this cap.  

There's formation of a renal or a metanephric  vesicle. So these vesicles, they become S-shaped,  

and one portion of this S gets associated with  capillaries. So that's going to form the glomerulus.

The rest of the S becomes the renal tubule. They  lengthen and they form the proximal convoluted  

tubule, the loop of Henle, and the distal convoluted  tubule. So we finally got a nephron. So the ureteric  

bud induces the metanephric blastema, and that in  turn induces the ureteric bud. So the ureteric bud  

forms the calyces, the renal pelvis, and the ureter.  So everything from the collecting duct downwards.  

And the metanephric blastema forms the  excretory portion, from the glomerulus to  

the distal convoluted tubule. As gestation  continues, the number of nephrons increase,  

because ultimately the kidneys have millions of  nephrons, remember? So the kidneys have developed in  

the pelvic region, but the kidneys ultimately are  going to be in the abdomen. And that's because with  

body growth, they ascend. So initially their blood  supply is from branches of the abdominal aorta,  

but finally the renal arteries come  directly off the abdominal aorta.

So during foetal life, when the kidneys function,  they form urine. That drains into the cloaca  

and then into the amniotic fluid. And that  is how the kidneys develop. Three stages  

pronephros, mesonephros, and metanephros.  If this video helped you, give it a thumbs  

up and subscribe to my channel. Thanks for  watching and I'll see you in the next one! :)