The Genitourinary (Urogenital) System Concept Help
Introduction to The Genitourinary (Urogenital) System Concept
In this section, we consider both the urinary ( YOUR -ih- nair -ee) and reproductive ( ree -proh- DUCK -tiv) systems. The urinary system literally “pertains to” (-ary) “urine” production, storage, and excretion from the individual body. The reproductive system in the male and female, on the other hand, is literally about “producing” a new organism, “again” (re-). For most animals, this implies using the genital ( JEN -ih-tal) organs to “beget or produce” (genit) sexually.
In humans and other mammals, it is appropriate to speak not just of the urinary and reproductive systems alone but of a combined genitourinary ( JEN -ih-toh- ur -ih- nair -ee) or urogenital ( UR -oh- jen -ih-tal) system. This is because many of the structures of the urinary and reproductive (genital) organs are shared in common. Consider, for example, the penis ( PEA -nis) in males. The penis is a spongy “tail” (pen) -like structure that serves both to carry urine out of the body, as well as deliver spermatozoa (sperm cells) to an ovum (mature egg cell) for reproduction.
Major Urinary Structures In Animals
In all vertebrates, the major organs of urine excretion are the kidneys. In humans, a pair of bean-shaped kidneys are located along either side of the vertebral column, deep within the back.
Figure 20.1 provides an overview of renal ( REE -nal) or “pertaining to” ( -al ) “kidney” ( ren ) anatomy. The kidney is encased within the renal capsule , a thin membrane of fibrous connective tissue. The kidney, itself, is subdivided into three major areas or zones. The outermost zone is called the renal cortex . Much as the cerebral cortex forms a thin “bark” over the surface of the cerebrum (Chapter 14), the renal cortex does the same for the kidney. The “middle” (medull) area is the renal medulla (meh- DEW -lah). And the deepest zone is the renal pelvis ( PEL -vis). The renal pelvis is a broad, bowl-shaped sac that receives the urine as it flows from the renal cortex and medulla. And carrying the collected urine of the renal pelvis is the ureter ( YOUR -eh- ter ).
Within the renal cortex are millions of nephrons ( NEF -rahns). The nephrons are the major microscopic functional units of the kidney. It is the nephrons that are actually responsible for formation of urine from the blood. Each nephron begins with a glomerulus (gluh- MAHR -yew- lus ). The glomerulus is a tiny, red-colored collection of renal capillaries. This structure gets its name from its resemblance to a little red “ball of yarn” (glomerul). The blood pressure pushing against the walls of the capillaries in each glomerulus, causes a filtration of fluid out of the glomerulus, and into the adjoining group of urinary tubules ( TWO -byools) – “tiny urine tubes.”
The urinary tubules from each group of neighboring nephrons eventually empty into a common passageway called a collecting duct . A number of collecting ducts pass down together through the renal medulla. They create the renal pyramids, which are pointed at their bottom tips like the rather blunt pyramids constructed by the Aztecs or Inca Indians. The tip of each renal pyramid drips urine into a renal calyx ( KAY -licks), or “kidney flower cup.” And the urine from each calyx eventually flows into the body of the renal pelvis, before it leaves the kidney via the ureter.
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