The Urinary System

Structures Kidneys Ureters Bladder Urethra

Function of Kidneys –Excrete toxins and nitrogenous wastes –Regulate levels of many chemicals in blood –Maintain water balance –Help regulate blood pressure

Kidneys Under back muscles Behind parietal peritoneum Just above waistline Right kidney usually a little lower than left

Inside the Kidneys Renal cortex Renal medulla Renal pyramids Renal pelvis –Major calyces –Minor calyces

Nephron Microscopic “Functional Unit” Renal corpuscle Bowman’s capsule Glomerulus Renal tubule Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting tubule

Ureters Narrow long tubes with expanded upper end (renal pelvis) inside kidney Lined with mucous Muscular layer in wall Drains urine from renal pelvis to bladder

Urinary Bladder Elastic muscular organ Capable of great expansion Stores urine before voiding

Urethra Narrow tube from urinary bladder to exterior Opening of urethra to the exterior called urinary meatus

Steps in UrineFormation Filtration Reabsorption Secretion

Micturition Passage of urine from body (also called urination or voiding) Regulatory sphincters –Internal urethral sphincter (involuntary) –External urethral sphincter (voluntary) Bladder wall permits storage of urine with little increase in pressure

Micturition Initiated by stretch reflex in bladder wall Bladder wall contracts Internal sphincter relaxes External sphincter relaxes, and urination

The Reproductive Systems

Male Reproduction System

Testes in scrotum lower temperature contain seminiferous tubules Spermatogenesis

Epididymis – Lies along the top of testis in the scrotum –Sperm mature, develop motility

Ductus (vas) deferens Receives sperm from the epididymis Primary function: transport seminal fluid Joins duct of seminal vesicle to form the ejaculatory duct

Seminal vesicles Glands Secretions provide energy needed by sperm for motility

Prostate gland Shaped like a doughnut and located below bladder Urethra passes through the gland Secretions create ongoing sperm motility

Bulbourethral (Cowper’s) glands Resemble peas in size and shape Secretions help to provide lubrication and neutralize acidity of vagina

Penis Three columns of erectile tissue –two dorsal: corpora cavernosa –one ventral: corpus spongiosum Glans penis covered by foreskin

Semen Fluid ejaculated from penis Nutrient rich environment for sperm Sperm –Acrosome –Tail

Female Reproductive System

Ovaries Resemble large almonds Attached to ligaments in pelvic cavity on each side of uterus Contain ovarian follicles

Uterine (fallopian) tubes Extend from near ovary to uterus Distal end: fimbriae Move oocyte from ovary to uterus

Uterus Body, fundus, and cervix Lies in pelvic cavity just behind urinary bladder Layers: –Myometrium is muscle layer –Endometrium lost in menstruation

Vagina Tube about 10 cm long Receives penis during sexual intercourse Birth canal for normal delivery of baby at end of pregnancy

Bartholin’s (greater vestibular) glands Secrete mucus-like lubricating fluid Ducts open between labia minora

External genitals Mons pubis Clitoris Urethral opening Bartholin’s gland Labia minora and majora Hymen Perineum

Breasts Located over pectoral muscles of thorax Size determined by fat quantity Lactiferous ducts drain at nipple, which is surrounded by pigmented areola

Menstrual cycle Many changes in the uterus, ovaries, vagina, and breasts Length –about 28 days –varies from month to month and person to person

Phases of Menstruation Menses –Sloughing of endometrium (uterine lining) Proliferative phase – Characterized by repair of endometrium Secretory phase –Preparing for implantation of ovum