<< Chapter < Page Chapter >> Page >
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.

Urethra

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

Skeletal muscles can be tetanized but not cardiac muscle.Discuss
Okeke Reply
what is regional anatomy?
Grace Reply
study of structures that contribute to specific body region
charles
what is grey matter
OJO Reply
What is neuron cell
Dev Reply
neuron cell are the fundamental units of the brain and nervous system responsible for receiving sensory input from the external world, for sending motor commands to muscles and for transforming and relaying the electrical signals at every step in between
Serphine
What is the perfect defination of Life
Dev
What does a word muscles means ?
Abubakar
what is Anatomy
Hannah Reply
because she's not yet at term
Nansi Reply
what is physiology?
Grace Reply
what is physiology
David
Physiology is the study of the functions of the human body
Hannah
am a new one!!
sekela
what is Homeopathy
AHMED
Name three reasons to study anatomy and physiology
Hills Reply
To know more about our body structure and functions this helps us To know disorders easily To get the medicine To appriciate the structure with the system and know that we are unique creatures
Tinbit
Why do we need to study anatomy and physiology
Hills Reply
I want to study human anatomy
Ibrahim
What is anatomy
Christabel Reply
anatomy is the branch of medicine in which we study structure and part of the body
Ansar
The art of studying the different parts of any organized body, to discover their situation, structure, and economy; dissection.
ChristMas
anatomy is the study of structures that make up the body and how they re realated to each other
BRIAN
Anatomy is the study of structures of the body and shape of the body and body parts and their relationship to one another.
Abubakar
what is the importance of anatomy
Emeria Reply
cockroch ka sir katne ke bad o jinda kyu rahta
Anil
it helps us to understand the function of human metabolic system and also who these systems works which system play what role and so on
Nouman
It's help us to know the structure, functions and relationship of the human body
Nansi
it helps us to appreciate how the internal structures works
Damilola
Anatomy opens up to us the structures of the various parts of the human body and correlates them to their specific function respectively
Michael
Anatomy is helps us understand and explore much about human structures
Chuks
systemic anatomy in short
Puja Reply
systemic circulation is the circulation in which heart supplies oxygenated blood to cells of body and takes deoxygenated blood away from body to heart
Ajeet
really?
Puja
yeah
BRIAN
ha ji
Ajeet
well much setisfy
Nouman
hello
Limpo
am new here
Limpo
ok
Emeria
am new here
Sindazi
I'm new as well
Crystal
who ask the question about cockroach cutting head
Nouman
the answer is They have an open circulatory system, which there's much less pressure in.After you cut their heads off very often their necks would seal off just by clotting," he adds. "There's no uncontrolled bleeding.The hardy vermin breathe through spiracles, or little holes in each body se
Nouman
does this platform helpful
Sindazi
well it's up-to you how you utilities this
Nouman
thnx ajeet
Puja
hello
AKARAJ
plz anatoy write note
AKARAJ
I think it is helpful
Alfred
Hi
Christabel
hi
Sachin
how do plateletes function in blood clotting
lydia
what are the function of the cell membrane
Elias Reply
the cell membrane helps in allowing and removing substances from the cell. it also aid in protecting the cell and giving it a definite shape.
veezy
The cell membrane is made up of a semipermeable lipid bi-layer which helps to regulate the kind of materials that enters it through active transport and passive diffusion.
Michael
properties of cardiac muscle
hotlan Reply
Myogenic,contain intercalated disc,control involuntary,fond in the heart walls only
AMOS
The exclusive characteristics of heart muscle is consists of Intercalated disc.
Doctor
Among the involuntary muscles only cardiac muscle is Myogenic but rest of involuntary muscles is Neurogenic.
Doctor
What about the exclusive characteristics of smooth muscle apart from lacking myofibrils in it's structure?
AMOS
What is the different between neurogenic and carcinogenic?
AMOS
distinguish between anatomy and physiology
Jonah Reply
Anatomy is the study of body parts and were they are found, physiology is the study of body parts and their functions
Alex
Anatomy is the scientific study of the body structure. While Physiology is the scientific study of the body function
Ossy
Anatomy is te scientic study of body parts and their physical relationship between different systems while physiology is te study of how all body systems works.
AMOS

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play




Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Anatomy & Physiology' conversation and receive update notifications?

Ask