The reproductive system has four main functions, namely; to produce egg and sperm cells (gametogenesis); to transport and sustain these cells; to nurture the developing offspring (during pregnancy); and to produce the hormones (such as estrogen, progesterone and testosterone) that regulate all of the above functions. The primary sex organs are responsible for gametogenesis, whilst the secondary organs meet the remaining three system functions. Female gametes (ova) are generated in a monthly, hormone-controlled cycle that begins at menarche.
Each month, follicles in the ovary respond to hormonal signalling and develop into ova, which are released into the uterus via the fallopian tubes. Sperm are produced continuously in the male testes and, if sexual intercourse occurs at the time of female ovulation, fertilisation may occur. The embryo implants in the thick, blood-rich lining of the uterus. Complex hormonal signalling governs the process of implantation, embryonic development, maintenance of pregnancy and birth. Pathology The consequence of pathologies of the reproductive system is often infertility.
Structural abnormalities of any part of the female reproductive tract, such as fallopian tube scarring or improper growth of the endometrial lining (endometriosis) may prevent a woman from conceiving. Similarly, obstructions to the male spermatic ducts may physically prevent proper ejaculation and therefore conception. In both males and females, a substantial proportion of reproductive system pathologies result from absent or improper hormonal signalling. For females, improper circulating levels of estrogen, progesterone or other gonadotrophic hormones may prevent the development or release of eggs during ovulation.
Improper hormonal levels may also result in spontaneous abortion, or may cause congenital abnormalities. Sex hormones also regulate the processes of puberty and attainment of sexual maturity. Hypo- or hyper-secretion of gonadotrophic hormones as a result of cancer, or from other inherited or acquired medical conditions, may cause the reproductive system to fail. Testicular failure often results from Klinefelter Syndrome, where males have an additional X chromosome. This causes low levels of testosterone, seminiferous tubule dysfunction, improper spermatogenesis and infertility.
Females may suffer from Turner’s Syndrome, where an X chromosome is missing. These women have sexual organs at birth, however these often regress and are absent by puberty. In addition to inherited disorders, function of the reproductive system may be compromised by environmental conditions, such as stress or poor nutrition. Voluntary dieting or excessive physical activity may often disrupt or ameliorate the female reproductive cycle. Urinary system Anatomy The system responsible for producing, storing and eliminating urine from the body is the urinary (or micturition) system.
It comprises two kidneys, two ureters, the bladder and the urethra. The kidneys are bean-shaped organs contained in the abdominal cavity, retroperitoneal to the digestive organs and adjacent to the spine at the T12 to L3 level. The adrenal glands are located at the superior pole of each kidney. There are approximately one million nephrons contained in the cortex and medulla of each adult kidney – these are the basic functional unit of the kidneys. Urine is transferred from the kidneys to the urinary bladder by the peristaltic contractions of the ureters.
The urinary bladder is a hollow, muscular organ that lies in the pelvic fossa. Transitional epithelial tissue associated with the bladder allows it to expand to accommodate a urinary volume of up to 500mL. Flow of urine from the bladder is restricted by two urinary sphincters and is assisted by contraction of the detrusor muscle. Urine is expelled from the bladder through the urethra, which terminates at the head of the penis in males and between the clitoris and vulva in females. Physiology The main role of the urinary system is to filter water soluble waste products from the blood.
To this end, the kidneys receive a supply of approximately 1. 25 liters of blood per minute from the renal arteries, which are direct tributaries of the abdominal aorta. The glomerular region of individual nephrons filter blood under pressure and reabsorb necessary fluid and electrolytes, such as sodium, potassium and calcium, whilst excreting other molecules such as urea. The glomerular filtration rate is a useful clinical indicator of renal function. Excretory balance is maintained by local and systemic hormones.
The kidneys contribute to acid-base homeostasis by the excreting bound acids and ammonium ions. As a result, blood pH is maintained at 7. 4. Depending on the balance of products excreted, urine is alternatively acidic (at an approximate pH of 5) or alkaline (approximately pH 8). Another important function of the kidney is to regulate blood pressure through the rennin-angiotensin system (Granger et al. ). When blood pressure drops, the kidneys secrete the enzyme renin, which activates a pathway that produces the hormone aldosterone.
Aldosterone increases sodium reabsorption in the kidneys and hence, water reabsorption. The increase in water reabsorption results in an increased blood volume and effectively, an increase in blood pressure. Pathology Congenital structural abnormalities or inherited pathologies, such as polycystic kidney disease or renal dysplasia may affect the function of the kidneys. Obstruction of the kidneys by kidney stones (renal calculi) is a common condition that often requires surgical correction.
Renal failure is a condition where the glomerular filtration rate of the kidneys is markedly reduced, causing an increase in blood creatine levels. Renal failure may either be acute or chronic. Chronic renal failure develops slowly, typically as the result of a pre-existing medical condition such as glomerulonephritis or pyelonephritis. By contrast acute renal failure is a rapid loss of kidney function as a result of damage to the kidneys. Acute renal failure is evidenced by a severe reduction in urine production.
The effects of both types of renal failure are metabolic acidosis (acidification of the blood), hyperkalemia (elevated blood potassium concentration) and changes in body water balance. Acute renal failure is serious and is treated as a medical emergency. In renal failure, artificial blood filtration, using a dialysis machine, is necessary to preserve life. Lymphatic/immune system Anatomy The immune system has components throughout the human body; however there are certain sites where immune cells are organized into specific structures.
These structures are either central lymphoid tissues (such as bone marrow or the thymus) or peripheral lymphoid tissues (lymph nodes, spleen, mucosa-associated lymphoid tissues). Lymphatic vessels are found throughout most of the body and have a similar architecture to blood vessels (Swartz). Lymphatic capillaries permeate body tissues and merge to form larger lymphatic veins. Lymph fluid from the right hand side of the body empties into the right lymphatic duct and lymph from the remainder of the body empties into the thoracic duct.
These ducts drain into the circulatory system at the left and right subclavian veins. Lymph nodes are situated along lymphatic vessels and are concentrated in various regions of the body, including the neck, axillary region (armpits), abdomen and groin. Lymphatic fluid is circulated under low pressure via peristaltic contractions and skeletal muscle movement. Backflow is prevented by one-way antilunar valves in lymph veins. Physiology The lymphatic system acts as a secondary, open circulatory system that collaborates with white blood cells to protect the body against infection (Swartz).
The system has three over-lapping functions, namely; to remove excess fluids from body tissues; to absorb fatty acids and transport fat and chyle to the circulatory system; and to produce immune cells such as lymphocytes, monocytes and plasma cells. Lymph originates as blood plasma that leaks from the permeable walls of the capillaries of the circulatory system. Although 90% of leaked plasma is forced back into the capillaries due to osmotic pressure, some fluid accumulates in the interstitial space. This fluid is collected by the lymphatic system and returned to the circulatory system.
Lymph vessels known as lacteals are contained in the mucosal lining of the gastrointestinal tract. Fats absorbed by the small intestine enter the lymphatic system via the lacteals. The enriched lymph originating from the small intestine is known as chyle and is processed by the liver, once it re-enters the circulatory system. The immune function of the lymph system is achieved by the accessory lymphoid tissues that comprise the lymphatic organs. Each of the organs, including the thymus and spleen, are structured to support B- and T-lymphocytes, macrophages and dendritic cells.
When infective microorganisms or antigens enter the body, the antigens are transported through the lymphatic system to the lymph nodes, where macrophages subsume the antigens and present them to lymphocytes. Upon recognition, additional immune cells are recruited to the lymph nodes to combat the infection. Pathology Elephantiasis and lymphadema are both common disorders of the lymphatic system. In elephantiasis, the parasite lymphatic filariasis causes thickening of the skin and underlying tissues, especially of the legs and genitals.
Lymphadema results from damage to or improper growth and development of the lymphatic system. It causes swelling of the arms and legs because fluid movement from the lymphatic to the circulatory systems is compromised. Initially, lymphadema is controllable by elevating the affected limbs, but untreated it causes fibrosis and eventually results in irreversible elephantiasis. The lymphatic system is also commonly subject to neoplasm. Lymphoma is a relative common type of cancer that originates in the lymphocytes.
Since the lymphatic system is part of the immune system, patients who are immuno-compromised, either from other illnesses or some medications, are at higher risk of developing lymphoma. Due to the systemic distribution of lymph system components, lymphoma spreads quickly and can be difficult to treat.
WORKS CITED Granger, J. P. , et al. “Endothelin, the Kidney, and Hypertension. ” Current Hypertension Reports 8. 4 (2006): 298-303. Swartz, M. A. “The Physiology of the Lymphatic System. ” Advanced Drug Delivery Reviews 50. 1-2 (2001): 3-20. Vickers, J. “The Heart (Part 2): Anatomy and Physiology. ” Nursing Times 95. 34 (1999): 46-9.