Academy of Diagnostic & Osteopathic Medicine
KIDNEYS
Kidneys: The Body’s Natural Filtration System Hidden beneath your lower ribs, on either side of your spine, are two bean-shaped powerhouses—the kidneys. They’re not just filters; they’re lifesavers, cleaning nearly 50 gallons of blood per day, balancing electrolytes, and regulating blood pressure. Each kidney is made up of thousands of microscopic filters, known as nephrons, working tirelessly to remove toxins, excess fluids, and waste products, sending them out as urine. Blood flows in through the renal arteries, straight from the abdominal aorta, delivering oxygen and nutrients. Once filtered, clean blood returns to circulation through the renal veins, feeding into the inferior vena cava. But what happens when things go wrong? Kidney stones—sharp, mineral deposits—can bring excruciating pain. Chronic Kidney Disease (CKD) can develop silently over time, often caused by diabetes and high blood pressure. Polycystic Kidney Disease (PKD), a genetic condition, fills the kidneys with cysts, threatening function and leading to kidney failure. The kidneys don’t just filter—they protect, regulate, and sustain life. Keep them healthy, and they’ll keep you going.
URETERS
Ureters: The Kidney’s Drainage System The ureters are two thin, muscular tubes that connect the kidneys to the bladder, running along the posterior abdominal wall. Each ureter is about 10-12 inches long and lined with smooth muscle to propel urine downward through peristalsis. Blood supply comes from the renal, gonadal, common iliac, and vesical arteries, while venous drainage flows into the renal and iliac veins. The ureters function as a one-way transport system, ensuring that urine moves from the kidneys to the bladder without backflow. Common issues include kidney stones, which can block urine flow and cause severe pain, ureteral strictures, which narrow the passage, and vesicoureteral reflux, where urine flows backward into the kidneys, increasing the risk of infections.
BLADDER
Bladder: The Body’s Urine Reservoir Your bladder is your personal storage tank, a hollow, muscular organ sitting in your pelvic cavity, just behind the pubic bone. It may not get much attention—until it demands it! It holds up to 500 mL of urine, expanding like a balloon as it fills. Lined with smooth muscle, known as the detrusor, it contracts when full, sending strong signals to your brain: “Time to go!” Its blood supply comes from the vesical arteries, feeding it from the internal iliac artery, while the vesical venous plexus carries waste away. But sometimes, things don’t go as planned: Urinary Tract Infections (UTIs)—caused by bacteria—bring burning pain and urgency. Bladder cancer, often linked to smoking or toxins, can form tumors in the lining. Interstitial cystitis, a chronic condition, causes persistent pain and frequent urination. Your bladder’s job is simple—store, hold, release—but when it’s not working right, you feel it.
URETHRA
Urethra: The Final Exit for Urine The urethra is a thin, muscular tube that carries urine from the bladder out of the body. In men, it passes through the prostate and penis, serving both the urinary and reproductive systems, while in women, it’s shorter and opens just above the vaginal opening. Blood supply comes from the internal pudendal and vesical arteries, with venous drainage into the pudendal veins. The urethra’s main function is to control urination, using sphincter muscles to regulate urine flow. Common conditions include urinary tract infections (UTIs), which cause burning and urgency, urethral strictures, which can obstruct urine flow, and incontinence, where bladder control is lost due to weakened muscles.
OVARIES
The ovaries are located in the pelvic cavity, one on each side of the uterus. These almond-shaped organs contain follicles, which develop into eggs, or ova, during a woman’s reproductive years. The ovaries are supplied by the ovarian arteries, which branch directly from the abdominal aorta. Venous drainage occurs through the ovarian veins, with the right ovarian vein draining into the inferior vena cava and the left ovarian vein draining into the left renal vein. The ovaries have two important functions: they produce eggs and they secrete hormones like estrogen and progesterone, which regulate the menstrual cycle and support pregnancy. Common conditions include polycystic ovary syndrome, or PCOS, a hormonal disorder that can cause irregular periods and cysts, and ovarian cancer, a malignancy often detected in later stages due to nonspecific symptoms.
ENDOMETRIUM
The endometrium is the innermost lining of the uterus. It has two main layers: the functional layer, which is shed during menstruation, and the basal layer, which regenerates the functional layer after each cycle. The endometrium is supplied by spiral arteries, which branch off the uterine arteries, and venous drainage occurs through the uterine venous plexus into the internal iliac veins. Its primary role is to provide a site for implantation of a fertilized egg and to nourish the developing embryo during early pregnancy. Common conditions affecting the endometrium include endometrial hyperplasia, an overgrowth of the tissue that can sometimes lead to cancer, and endometrial cancer, a common gynecological malignancy often signaled by abnormal bleeding.
BREAST
The breasts are located on the chest wall, sitting over the pectoral muscles. They are composed of lobes, lobules, ducts, and fatty tissue known as adipose tissue, which gives the breast its shape. The breasts receive blood supply from the internal thoracic and lateral thoracic arteries, and venous drainage occurs through the internal thoracic and axillary veins. The primary function of the breast is to produce and deliver milk for feeding infants through a process called lactation. Common breast conditions include breast cancer, which often originates in the ducts or lobules, and mastitis, an infection of the breast tissue that frequently occurs during breastfeeding.
SCROTUM
The scrotum is an external pouch located below the penis. It contains the testes, epididymis, and spermatic cord, all of which are essential for male reproductive function. The scrotum is supplied by the testicular arteries, which branch from the abdominal aorta, and venous drainage occurs through the pampiniform venous plexus into the testicular veins. Its main function is to protect and regulate the temperature of the testes, ensuring optimal conditions for sperm production. Common scrotal conditions include varicocele, which is an enlargement of the veins in the scrotum that can lead to infertility, and hydrocele, a fluid buildup around the testes that causes swelling.
UTERUS
The uterus is located in the pelvic cavity, positioned behind the bladder and in front of the rectum. It’s divided into three main parts: the fundus, which is the upper dome-shaped part; the body, which makes up most of the uterus; and the cervix, which connects to the vagina. The uterus is lined by the endometrium, a tissue that changes during the menstrual cycle. Blood is supplied to the uterus by the uterine arteries, which are branches of the internal iliac arteries, and venous blood is drained through the uterine veins into the internal iliac veins. The uterus supports fetal development during pregnancy and sheds its lining during menstruation when pregnancy does not occur. Common uterine conditions include fibroids, which are non-cancerous growths that can cause pain or heavy periods, and endometriosis, where endometrial tissue grows outside the uterus, leading to pain and infertility.
VAGINA
Vagina: The Birth Canal and Reproductive Passage The vagina is a muscular, elastic canal that connects the external genitalia (vulva) to the cervix and uterus. It is located in the pelvic cavity, sitting between the bladder and rectum. The vaginal walls contain rugae, which allow for expansion during childbirth and intercourse. Blood supply comes from the vaginal artery, a branch of the internal iliac artery, while venous drainage occurs through the vaginal venous plexus into the internal iliac vein. Its primary functions include receiving the penis during intercourse, serving as the birth canal, and allowing for menstrual flow to exit the body. It is also home to beneficial bacteria, which help maintain a healthy pH balance. Common conditions include vaginitis, an inflammation caused by infections or hormonal changes, pelvic organ prolapse, where weakened muscles cause the vaginal walls to drop, and vaginal atrophy, often occurring after menopause due to low estrogen levels.
PROSTATE
The prostate is located below the bladder and surrounds the urethra. It is made up of both glandular and muscular tissue and is divided into three zones: the central, peripheral, and transition zones. The prostate is supplied with blood from the inferior vesical and middle rectal arteries, and venous drainage occurs through the prostatic venous plexus into the internal iliac vein. Its primary function is to produce seminal fluid, which nourishes and transports sperm during ejaculation. Two common prostate conditions include benign prostatic hyperplasia, or BPH, a non-cancerous enlargement of the prostate that causes urinary problems, and prostate cancer, a malignant tumor often detected through PSA levels or a biopsy.
TESTES
Testes: The Sperm and Hormone Factory The testes, or testicles, are two oval-shaped glands located inside the scrotum, just below the penis. They are responsible for sperm production and testosterone secretion, playing a vital role in reproduction and male development. Each testis is covered by the tunica albuginea, a protective layer that helps maintain structure. Blood is supplied by the testicular arteries, which branch from the abdominal aorta, and venous drainage occurs through the pampiniform venous plexus, which helps regulate temperature. The testes function as the male reproductive organs, producing sperm cells in the seminiferous tubules and releasing testosterone, which drives muscle growth, libido, and secondary male characteristics. Common conditions include varicocele, where enlarged veins can affect fertility, testicular torsion, a medical emergency caused by twisted spermatic cords, and testicular cancer, which often presents as a painless lump.
PENIS
Penis: The Male Reproductive Organ The penis is the external male genital organ, responsible for urination, sexual function, and sperm delivery. It consists of three cylindrical structures—the corpora cavernosa, which fill with blood during arousal, and the corpus spongiosum, which surrounds the urethra and prevents compression during erection. Blood is supplied by the internal pudendal artery, with venous drainage into the deep dorsal vein of the penis. Its function is to act as a conduit for urine and semen, using the urethra for both functions. During sexual arousal, the erectile tissue fills with blood, allowing for penetration and ejaculation. Common issues include erectile dysfunction (ED), where blood flow is impaired, Peyronie’s disease, which causes curvature due to fibrous plaque buildup, and priapism, a prolonged, painful erection requiring urgent treatment.