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By the end of this section, you will be able to:
  • Identify the ureters, urinary bladder, and urethra, as well as their location, structure, histology, and function
  • Compare and contrast male and female urethras
  • Describe the micturition reflex
  • Describe voluntary and involuntary neural control of micturition

Rather than start with urine formation, this section will start with urine excretion. Urine is a fluid of variable composition that requires specialized structures to remove it from the body safely and efficiently. Blood is filtered, and the filtrate is transformed into urine at a relatively constant rate throughout the day. This processed liquid is stored until a convenient time for excretion. All structures involved in the transport and storage of the urine are large enough to be visible to the naked eye. This transport and storage system not only stores the waste, but it protects the tissues from damage due to the wide range of pH and osmolarity of the urine, prevents infection by foreign organisms, and for the male, provides reproductive functions.


The urethra    transports urine from the bladder to the outside of the body for disposal. The urethra is the only urologic organ that shows any significant anatomic difference between males and females; all other urine transport structures are identical ( [link] ).

Female and male urethras

The top panel of this figure shows the organs in the female urinary system.
The urethra transports urine from the bladder to the outside of the body. This image shows (a) a female urethra and (b) a male urethra.

The urethra in both males and females begins inferior and central to the two ureteral openings forming the three points of a triangular-shaped area at the base of the bladder called the trigone    (Greek tri- = “triangle” and the root of the word “trigonometry”). The urethra tracks posterior and inferior to the pubic symphysis (see [link] a ). In both males and females, the proximal urethra is lined by transitional epithelium, whereas the terminal portion is a nonkeratinized, stratified squamous epithelium. In the male, pseudostratified columnar epithelium lines the urethra between these two cell types. Voiding is regulated by an involuntary autonomic nervous system-controlled internal urinary sphincter    , consisting of smooth muscle and voluntary skeletal muscle that forms the external urinary sphincter    below it.

Female urethra

The external urethral orifice is embedded in the anterior vaginal wall inferior to the clitoris, superior to the vaginal opening (introitus), and medial to the labia minora. Its short length, about 4 cm, is less of a barrier to fecal bacteria than the longer male urethra and the best explanation for the greater incidence of UTI in women. Voluntary control of the external urethral sphincter is a function of the pudendal nerve. It arises in the sacral region of the spinal cord, traveling via the S2–S4 nerves of the sacral plexus.

Male urethra

The male urethra passes through the prostate gland immediately inferior to the bladder before passing below the pubic symphysis (see [link] b ). The length of the male urethra varies between men but averages 20 cm in length. It is divided into four regions: the preprostatic urethra, the prostatic urethra, the membranous urethra, and the spongy or penile urethra. The preprostatic urethra is very short and incorporated into the bladder wall. The prostatic urethra passes through the prostate gland. During sexual intercourse, it receives sperm via the ejaculatory ducts and secretions from the seminal vesicles. Paired Cowper’s glands (bulbourethral glands) produce and secrete mucus into the urethra to buffer urethral pH during sexual stimulation. The mucus neutralizes the usually acidic environment and lubricates the urethra, decreasing the resistance to ejaculation. The membranous urethra passes through the deep muscles of the perineum, where it is invested by the overlying urethral sphincters. The spongy urethra exits at the tip (external urethral orifice) of the penis after passing through the corpus spongiosum. Mucous glands are found along much of the length of the urethra and protect the urethra from extremes of urine pH. Innervation is the same in both males and females.

Questions & Answers

what is the difference between plasma and serum
Gloria Reply
Plasma contains fibrinogen while serum doesn't
plasma ----- fibrinogen = serum
In what time stomach empty it's content in to doudemun? what is chyme?
Sneha Reply
write the chemical and mechanical digestion which occurs in stomach?
Does absorption take place in stomach? what are absorption in the stomach by which cell?
Chemical digestion---Mixtures of the food with the gastric acid Mechanical digestion--- churning of the food in the stomach making it become more involved into chyme
absorption takes place in the small intestine because of the presence of the villi
name the muscles supplied redina nerve
Appu Reply
mechanism of hormone releasing by gland
said Reply
why is muscle tissue not considered to be a type of connective tissue?
Ezel Reply
A Skeletal muscles consist of numerous muscles cells called Muscle Fibers . Three layers of connective tissues surrounded these fibers to make the muscles tissues
that's wny connective tissues is not considered as muscles fibers
there are 4 types of tissues : epithelial, connective tissue, nervous tissue and muscle tissue, each one has its own properties. The main function of connective tissue is nutrition, it supplies nutrientes to epithelial tissues that are responsible for protection.
Muscle tissue has properties that allow movement, the function here is movement and not nutrition like connective tissue.
In what time stomach empty it's content in to doudemun?
write the chemical and mechanical digestion which occurs in stomach?
Does absorption take place in stomach? what are absorption in the stomach by which cell?
Does absorption take place in stomach? what are the absorption in the stomach by which cell?
mechanism of hormone controlling releasing by gland
please can someone explain renin angiotensin aldosteron system for me
name the joint present between epichysif and diachysif
what is arteries
oxygenated blood carrying vessels
I think oxygenated blood carrying pulmonary vein
ya this stetment is right 4 pulmonary vein carrying the oxygenated blood
What is the relation between cold and clammy skin and disorders that cause poor perfusion?
Tyrone Reply
name the instruments used to measure the gas volume and flow in pulmonary function test
Preethi Reply
In a spirometry test, While you are sitting, you breath into a mouthpiece that is connected to an instrument called a spirometer . The spirometer records the amount and the rate of air that you breath in and out over a period of time. When standing, Some numbers might be slightly different.
tq soo much
u most wlcm
what is signal transduction?
Signal Transduction (Also know as cell signaling) is the transmission of molecular signal from a cell exterior to its interior.Signals receive by cells must be transmitted effectively into the cell to ensure an appropriate response. This step is initiated by cell - surface receptors.
i know now didn't know
that's great respond
what is histological anatomy?
Thelma Reply
what is histological anatomy?
the study of form of structure seen under the microscope
is the branch of biology which studies the microscopic anatomy of biological tissues.
it's the study of the microscopic anatomy of cells and tissues in the plants and it's carried out by examining a thin slice of tissues under a microscope light / or an electronic microscope
is the study of anatomy in a microscopic level
thank you
what are the significance differrences can be donated between the female and male skeleton..
What is Ions and Ionic bonds
Ravi Reply
2 less stable atoms
Ionic bonding is the complete transfer of valence electron(s) between atoms. It is a type of chemical bond that generates two oppositely charged ions. In ionic bonds, the metal loses electrons to become a positively charged cation, whereas the nonmetal accepts those electrons to become a negatively
what is osmosis
Brown Reply
it's out Body Fluid.
high pressure to low pressure flow
Osmosis is the movement of solvent from a region of lower solute concentration to a region of higher solute concentration through a semi- permeable membrane.
how many types of tissue
4, that is muscle tissue, connective, nerve and epithelial tissue
We have four types of tissue these are ,epithelial tissue,nerve tissue,muscle tissue and connective tissue
function of labia minora
why is a graph of plasma [glucose] superimposed
Sefai Reply
what is biosphere
Jenessa Reply
supporting life
it is the part of the earth and its atmosphere capable of supporting life
what is the function of villus?
Grant Reply
absorption of nutrients
They have a large surface area so there will be more efficient absorption of fatty acids and glycerol into the blood stream.
what is the relationship between heart and lungs
when blood inter the rihgt ventricle the blood is inpure through the pumps blood rich the luns there blood exchange pure
blood ( inpure blood exchange in to pure blood
I don't understand what these messages are about.
I gave you all the information I could think of. What is next?

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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