ANAT Week 12.docx

Week 12 **Module: Urinary System** **Ureters** ----------- ***LO5: Describe the location, function, gross anatomy and histology of the ureters*** **Now we are going to look at the three remaining organs of the urinary system that are collectively referred to as the urinary tract, which are the u...

Week 12 **Module: Urinary System** **Ureters** ----------- ***LO5: Describe the location, function, gross anatomy and histology of the ureters*** **Now we are going to look at the three remaining organs of the urinary system that are collectively referred to as the urinary tract, which are the ureters, urinary bladder and urethra. Unlike the wall of the gastrointestinal (GI) tract which has four layers, the wall of the urinary tract has three layers -- an inner mucosa, a middle muscularis and an outer serosa or adventitia, depending on the organ. We are going to look at the composition of these three layers in the ureters and urinary bladder as we look at their structure, starting with the ureters.** **The ureters are the tubes that transport urine from the kidneys to the urinary bladder. Like the kidneys, they sit directly against the posterior abdominal wall and are therefore only covered by parietal peritoneum on their anterior surface, making them retroperitoneal. Each ureter originates at the renal pelvis as it exits the hilum of the kidney and terminates by entering the urinary bladder.** **Now we are going to look at the unique composition of the three layers in the wall of the ureters.** **Click on each layer below to learn more about them.** **Mucosa** ---------- **The mucosa is composed of transitional epithelium with an underlying lamina propria made of fibroelastic connective tissue, which allows the ureters to stretch when they fill with urine. The mucosa is folded, which gives the ureters a star-shaped lumen. These folds allow the size of the lumen to increase considerably when the ureters are stretched.** **Muscularis** -------------- **The muscularis consists of two smooth muscle layers -- an inner longitudinal layer and an outer circular layer. This is the opposite arrangement to what is seen in the wall of the GI tract.** **Adventitia** -------------- **The outer layer of the ureters is an adventitia composed of areolar connective tissue, as the ureters are retroperitoneal. This helps to anchor the ureters to the posterior abdominal wall.** **Urinary Bladder** ------------------- ***LO6: Describe the location, anatomical relations, function, gross anatomy and histology of the urinary bladder*** **The second organ of the urinary tract is the urinary bladder, which is the muscular sac that stores urine until it is ready to be expelled from the body. The urinary bladder is located in the pelvic cavity directly posterior to the pubic symphysis, but can ascend slightly into the abdominal cavity when it is full.** **Now we are going to look at the anatomical relations of the urinary bladder in both males and females.** **Click on each of the cards below to learn about these relations.** **Male** **In males, the urinary bladder sits directly anterior to the rectum and superior to the prostate gland.** **Female** **In females, the urinary bladder sits anteroinferior to the uterus and directly anterior to the vagina.** **Now we are going to look at the features of the urinary bladder. When it is empty, the urinary bladder is shaped like an upside-down pyramid. It has an apex which points anteriorly and a base which is directed posteriorly. The ureters enter the urinary bladder at its two posterolateral angles. The neck of the urinary bladder is located inferiorly and is where it drains urine into the urethra to be expelled from the body. Internally on the posteroinferior aspect of the urinary bladder, there is a triangular region called the trigone which is defined by the two ureteric openings in the superior corners and the urethral opening in the inferior corner. This area is smooth, unlike the rest of the internal surface which has mucosal folds called rugae. The muscle in the wall of the urinary bladder is called the detrusor muscle.** **Now we are going to look at the unique composition of the three layers in the wall of the urinary bladder.** **Click on each layer below to learn more about them.** **Mucosa** ---------- **The mucosa is composed of transitional epithelium with an underlying lamina propria. It is folded to form rugae, which increases the distensibility of the urinary bladder. The rugae flatten out when the bladder fills with urine. The mucosa lacks these folds in the area of the trigone.** **Muscularis** -------------- **The muscularis consists of a smooth muscle called the detrusor muscle that is arranged in three layers -- an inner longitudinal layer, a middle circular layer and an outer longitudinal layer. The addition of a third smooth muscle layer allows the urinary bladder to squeeze urine out when the detrusor muscle contracts during micturition.** **Adventitia/Serosa** --------------------- **The outer layer of the urinary bladder is mostly an adventitia composed of areolar connective tissue, as it lies outside of the peritoneal cavity. However, its superior surface is covered by parietal peritoneum, making the outer layer in this region a serosa composed of simple squamous epithelium with underlying areolar connective tissue.** **Urethra** ----------- ***LO7: Compare and contrast the function and gross anatomy of the male and female urethras*** **The third and final organ of the urinary tract is the urethra, which is the tube that transports urine from the urinary bladder to expel it from the body. It originates at the neck of the urinary bladder, where a circular thickening of the detrusor muscle forms a structure called the internal urethral sphincter. This is an involuntary sphincter that keeps the urethra closed when urine is not being expelled. The urethra is guarded by another sphincter called the external urethral sphincter, which is located in a sheet of muscle called the urogenital diaphragm. This is a voluntary sphincter composed of circularly arranged skeletal muscle fibres. Both the internal and external urethral sphincters relax during micturition, allowing urine to be expelled from the body. The urethra opens to the exterior of the body at an opening called the external urethral orifice.** **The structure of the urethra is different in males and females.** ### **Female Urethra** **We are going to look at the female urethra first. The female urethra is very short, being only around 3 to 5 centimetres in length. It is guarded by the involuntary internal urethral sphincter at its origin from the neck of the urinary bladder and by another sphincter at its inferior end called the external urethral sphincter. This is a voluntary sphincter composed of circularly arranged skeletal muscle fibres and is located in a sheet of muscle called the urogenital diaphragm. It prevents urine from being expelled from the body until an individual decides to urinate, when they can voluntarily relax this sphincter. The only function of the female urethra is to transport urine out of the body.** ### **Male Urethra** **Now we are going to look at the male urethra. Unlike the female urethra, the male urethra has two functions, which are to transport urine out of the body during micturition and conduct semen during ejaculation. It is important to note that it does not carry urine and semen at the same time. The male urethra is very long, being around 18 to 20 centimetres in length. It can be divided into three regions that are named according to the structures they pass through.** **Click on the hotspots on the image below to learn more about these three parts.** **Module: Male Reproductive System** ==================================== **Learning Outcomes** --------------------- **By the end of this module, you should be able to:** **LO1: Name the main components and describe the basic functions of the male reproductive system** **LO2: Briefly describe the embryological development of the testes** **LO3: Describe the location, function and gross anatomy of the scrotum and spermatic cord** **LO4: Describe the location, function, external and internal anatomy of the testes** **LO5: Describe the location, function and gross anatomy of the epididymis, ductus deferens and ejaculatory duct** **LO6: Describe the location, function and gross anatomy of the accessory glands of the male reproductive system** **LO7: Describe the function and gross anatomy of the penis** **Components and Functions** ---------------------------- ***LO1: Name the main components and describe the basic functions of the male reproductive system*** **The male reproductive system is composed of the testes, which are the male primary sex organs or gonads, as well as accessory structures including the scrotum, epididymis, ductus deferens, ejaculatory duct, prostate gland, seminal vesicles, bulbourethral glands and penis.** **The male reproductive system has several functions, which are the production of gametes or sex cells, the production of sex hormones and the facilitation of fertilisation.** **Click on the hotspots below to learn more about these functions.** **Embryological Development of the Testes** ------------------------------------------- ***LO2: Briefly describe the embryological development of the testes*** **Now that we have introduced the main components of the male reproductive system and looked at its basic functions, we are going to look at its development, focusing specifically on the testes. Recall from the Embryology module that all tissues in the body are derived from the three primary germ layers of the embryo, which then arrange themselves to form organs. The primary germ layer that the components of the male reproductive system are derived from, including the testes, is the mesoderm.** **The male and female reproductive systems develop from the same primitive structures that differentiate into either male or female structures depending on genetic expression. In the fifth week of development, paired structures called genital ridges, or gonadal ridges, form from the mesoderm. These ultimately form the gonads, which are the testes in a male. The genital ridges form in the abdominal cavity at around the level of the tenth thoracic vertebra. During development, the resulting gonads, in this case the testes, will descend to their final position, which in the case of the testes is the scrotum. They descend by passing through a canal in the groin region called the inguinal canal. Each gonad is guided to its final position by a thin band of connective tissue called the gubernaculum. In a male, this will ultimately form a structure called the scrotal ligament, which tethers each testis to the scrotum internally.** **You may like to watch this short video to learn more about the descent of the testes through the inguinal canal into the scrotum (please note that the details regarding the layers of the spermatic cord are not examinable).** **Scrotum and Spermatic Cord** ------------------------------ ***LO3: Describe the location, function and gross anatomy of the scrotum and spermatic cord*** **Now that we have looked at the development of the testes, we are going to look at the scrotum and the spermatic cord. The scrotum is the cutaneous sac that the testes are located in and together with the penis, forms the external genitalia of the male. The testes sit outside the trunk of the body in the scrotum because the ideal temperature for sperm production is around 2-3 degrees Celsius lower than normal internal body temperature. The scrotum provides the cooler environment needed for normal sperm production. The spermatic cord is the structure that carries the ductus deferens (an accessory male reproductive structure which we will look at later in this module) as well as blood vessels, nerves and lymphatic vessels between the testes and the abdominopelvic cavity. It does so by travelling through the inguinal canal, which is the canal in the groin region that the testes passed through in their descent to the scrotum during development.** **There are two muscles that responds to changes in temperature to keep the testes at the ideal temperature for sperm production, which are the dartos muscle and the cremaster muscle.** **Click on the hotspots on the image below to learn more about these muscles.** **Testes** ---------- ***LO4: Describe the location, function, external and internal anatomy of the testes*** **Now we are going to look at the testes themselves. The testes are paired, oval-shaped organs located within the scrotum. Their function is the produce the male gametes and sex hormones. Externally, each testis is covered by a serous membrane called the tunica vaginalis and another layer of tissue called the tunica albuginea. Internally, each testis is divided into smaller sections called lobules, which contain highly coiled structures called seminiferous tubules.** **Click on the hotspots on the image below to learn more about these external and internal features.** **Epididymis, Ductus Deferens and Ejaculatory Duct** ---------------------------------------------------- ***LO5: Describe the location, function and gross anatomy of the epididymis, ductus deferens and ejaculatory duct*** **Now that we have looked at the testes, we are going to look at the accessory structures of the male reproductive system, starting with the set of ducts that store and transport sperm. This duct system begins in the testes and the union of many small ducts in each testis ultimately forms a highly coiled duct within a structure called the epididymis. The duct of the epididymis is continuous with another structure called the ductus deferens. The ductus deferens then unites with the duct of one of the accessory glands of the male reproductive system to form the ejaculatory duct. The ejaculatory duct opens into the prostatic urethra, which is how sperm will ultimately be ejaculated during sexual intercourse to enter the female reproductive tract and fertilise an oocyte.** **Click on the hotspots on the image below to learn more about each component of this duct system.** **Accessory Glands** -------------------- ***LO6: Describe the location, function and gross anatomy of the accessory glands of the male reproductive system*** **Now that we have looked at the ducts of the male reproductive system, we are going to look at the accessory glands. The function of the accessory glands is to produce secretions that collectively form seminal fluid. When seminal fluid is combined with sperm, it forms semen which is ejaculated during sexual intercourse. The secretions within the seminal fluid provide nourishment to the sperm as they travel through the female reproductive tract and neutralise the acidity of the vagina to protect the sperm. The accessory glands are the seminal vesicles, prostate gland and bulbourethral glands.** **Click on the hotspots on the image below to learn more about these glands.** **Penis** --------- ***LO7: Describe the function and gross anatomy of the penis*** **Now that we have looked at the accessory glands of the male reproductive system, we are going to look at the penis, which together with the scrotum forms the external genitalia of the male. It is also the male copulatory organ that is received by the vagina during sexual intercourse. The penis is composed of erectile tissue that contains a network of venous spaces that fill with blood during sexual arousal, causing an erection. Semen is then ejaculated from the penis via the urethra.** **The penis has three parts, which are the root, body and glans.** **Click on the hotspots on the image below to learn more about these three parts.** **Fertilisation Video** ----------------------- **Now that we have looked at all the components of the male reproductive system, you may like to watch the video below on the journey from fertilisation to birth to learn more about the path that sperm take from the testes, through the male reproductive tract and then into and through the female reproductive tract to reach an ovulated oocyte, where only one sperm will ultimately be able to fertilise the oocyte. Please note that you only need to watch up until approximately 2.30 for the content that is relevant to this module, but the content between approximately 4.00 and 6.30 is relevant to the embryology module. Everything else is for interest only and is not examinable.** **Module: Female Reproductive System** ====================================== **Learning Outcomes** --------------------- **By the end of this module, you should be able to:** **LO1: Name the main components and describe the basic functions of the female reproductive system** **LO2: Briefly describe the embryological development of the ovaries** **LO3: Describe the location, function, external and internal anatomy of the ovaries** **LO4: Describe the location, function and gross anatomy of the uterine tubes** **LO5: Describe the location, normal position and anatomical relations, function and gross anatomy of the uterus** **LO6: Describe the anatomical relations, function and gross anatomy of the vagina** **LO7: Describe the gross anatomy of the vulv** **Components and Functions** ---------------------------- ***LO1: Name the main components and describe the basic functions of the female reproductive system*** **The female reproductive system is composed of the ovaries, which are the female primary sex organs or gonads, as well as accessory structures including the uterine tubes, uterus, vagina and vulva. Collectively, the uterine tubes, uterus and vagina are referred to as the female reproductive tract. The mammary glands are also part of the female reproductive system, although we will not be looking at these in this module.** **The female reproductive system has several functions, which are the production of gametes or sex cells, the production of sex hormones, the facilitation of fertilisation and the support of foetal growth, development and delivery.** **Click on the hotspots below to learn more about these functions.** **Embryological Development of the Ovaries** -------------------------------------------- ***LO2: Briefly describe the embryological development of the ovaries*** **Now that we have introduced the main components of the female reproductive system and looked at its basic functions, we are going to look at its development, focusing specifically on the ovaries. Recall from the Embryology module that all tissues in the body are derived from the three primary germ layers of the embryo, which then arrange themselves to form organs. The primary germ layer that the components of the female reproductive system are derived from, including the ovaries, is the mesoderm.** **The female and male reproductive systems develop from the same primitive structures that differentiate into either female or male structures depending on genetic expression. In the fifth week of development, paired structures called genital ridges, or gonadal ridges, form from the mesoderm. These ultimately form the gonads, which are the ovaries in a female. The genital ridges form in the abdominal cavity at around the level of the tenth thoracic vertebra. During development, the resulting gonads, in this case the ovaries, will descend to their final position, which in the case of the ovaries is the pelvic cavity. Each gonad is guided to its final position by a thin band of connective tissue called the gubernaculum. In a female, this will ultimately form two ligamentous structures called the ovarian ligament and the round ligament of the uterus. We will learn more about these structures later in this module.** **Ovaries** ----------- ***LO3: Describe the location, function, external and internal anatomy of the ovaries*** **Now that we have looked at the development of the ovaries, we are going to look at them more closely. The ovaries are paired, oval-shaped organs that are around the size of an almond. They are located in the pelvic cavity lateral to the uterus, where they are supported by structures including the ovarian ligament, which we came across when we looked at the development of the ovaries, and the suspensory ligament. The function of the ovaries is to produce the female gametes and sex hormones. Externally, each ovary is covered by two layers of tissue, which are the germinal epithelium and the tunica albuginea. Eternally, each ovary has an outer region called the cortex and an inner region called the medulla.** **Click on the hotspots on the image below to learn more about these external and internal features.** **Uterine tubes** ----------------- ***LO4: Describe the location, function and gross anatomy of the uterine tubes*** **Now that we have looked at the ovaries, we are going to look at the organs of the female reproductive system that are collectively referred to as the female reproductive tract, starting with the uterine tubes.** **The uterine tubes are also referred to as the fallopian tubes or oviducts. They extend laterally from either side of the uterus and transport the ovulated oocyte to the uterus. Each uterine tube can be divided into four main parts. From lateral (i.e.closest to the ovaries) to medial (i.e. closest to the uterus), these are the infundibulum, ampulla, isthmus and uterine part.** **Click on the hotspots on the image below to learn more about these four main parts.** **Uterus** ---------- ***LO5: Describe the location, normal position and anatomical relations, function and gross anatomy of the uterus*** **The second organ of the female reproductive tract is the uterus, which is the muscular organ that supports, protects and nourishes the embryo and then foetus that grows and develops from a fertilised oocyte. If the oocyte is not fertilised, it is shed along with the inner lining of the uterus in the process of menstruation. The uterus is a pear-shaped organ located in the pelvic cavity, but it ascends into the abdominal cavity as it becomes larger during pregnancy. It communicates with the uterine tubes superolaterally and the vagina inferiorly. Normally, the uterus sits posterosuperior to the urinary bladder and anterior to the rectum with its neck, called the cervix, sitting in between the urinary bladder and the rectum and its body sitting across the superior surface of the urinary bladder.** **Now that we have looked at the general location and the normal position and anatomical relations of the uterus, we are going to look at its features. The uterus can be divided into four main parts, which are the fundus, body, isthmus and cervix.** **Click on the hotspots on the image below to learn more about these four main parts.** **There are several structures that support the uterus, including the round ligament of the uterus which we came across when we looked at the development of the ovaries, as well as a structure called the broad ligament.** **Click on the hotspots on the image below to learn more about these structures.** **Vagina** ---------- ***LO6: Describe the anatomical relations, function and gross anatomy of the vagina*** **The third and final organ of the female reproductive tract is the vagina, which is the fibromuscular canal that connects the uterus to the external environment. As such, it forms part of the birth canal for the delivery of the foetus during childbirth and provides the passageway for menstrual fluid. It is also the female copulatory organ that receives the penis during sexual intercourse. The vagina is located posterior to the urinary bladder and urethra and anterior to the rectum. The external opening of the vagina is called the vaginal orifice and is partially guarded by a vascularised, membranous structure called the hymen.** **Vulva** --------- ***LO7: Describe the gross anatomy of the vulva*** **Now that we have looked at the female reproductive tract, we are going to look at the vulva, which is the external genitalia of the female. The vulva includes several components, which are the mons pubis, labia majora, labia minora, vestibule and clitoris.** **Click on the hotspots on the image below to learn more about these components.** **Fertilisation Video** ----------------------- **Now that we have looked at all the components of the female reproductive system, you may like to watch the video below on fertilisation to learn more about the path that sperm take through the female reproductive tract to reach an ovulated oocyte, where only one sperm will ultimately be able to fertilise the oocyte (please note that the details regarding the process of fertilisation itself are not examinable).**