Urinary Bladder Anatomy

• The urinary bladder is a muscular sac (vesicle) used for urine storage.
• Normal bladder volume is 220ml, though it can tolerate 500ml of urine.
• In adults, when empty, the bladder is entirely within the lesser pelvis. When distended, it expands into the abdominal cavity.
• In children, the bladder is in the lesser pelvis and abdominal cavity, even when empty.

Bladder Shape and Surfaces

• The bladder is triangular pyramid-shaped.
• It has a base (fundus), neck, and apex.
• The bladder has one superior and two inferolateral surfaces.
• Only the superior surface is covered by peritoneum.
• A distended bladder expands into the abdominal cavity and may reach the umbilicus.
• Surgically, a distended bladder can be accessed through incisions or punctures in the anterior abdominal wall without traversing the peritoneum.

Apex and Superior Surface

• The apex is the anterior end, directed forwards and upwards towards the umbilicus (median umbilical ligament and fold).
• The superior surface is triangular, with lateral borders running from the apex backwards to the entrance of the ureter into the bladder.
• The superior surface is covered by peritoneum, except in the female, where the very posterior part lacks peritoneum and relates to the supravaginal part of the cervix.

Superior Surface in Males and Females

• In males, the peritoneum is reflected from the posterior border of the bladder to the rectum, forming the rectovesical pouch, with located paravesical fossae on the sides of this pouch.
• In females, the peritoneum is reflected from the bladder to the uterus, forming the vesicouterine pouch.

Fundus (base)

• The fundus is directed backwards and downwards.
• In females, it relates to the vagina.
• In males, it relates to the rectum, with the upper part forming the rectovesical pouch.
• The lower part of the fundus in males contains seminal vesicles & deferent ducts, and the tissue between is called the rectovesical fascia.

Bladder Neck

• The bladder neck is the lowest region.
• It is pierced by the internal orifice of the urethra.
• In males, it rests on the base of the prostate.
• In females, it rests on the pelvic fascia.

Inferolateral Surfaces

• The inferolateral surfaces face anteroinferiorly.
• They relate to the posterior surface of the pubis and are filled with adipose tissue (retropubic pad).
• In males, these surfaces connect to the puboprostatic ligament.
• In females, they connect to the pubovesical ligament.

Bladder Ligaments

• All bladder surfaces except the superior surface (peritoneum) are connected to other structures by fibroareolar tissue.
• On each side of the bladder are the lateral true ligaments.
• Anteriorly, there are puboprostatic ligaments (pubovesical ligaments.)
• At the apex, there is the median umbilical ligament (urachus).
• Posteriorly, there is the posterior ligament.
• False ligaments are folds of peritoneum, including the Median umbilical fold and Medial umbilical folds( 2 in number).

Internal Surface of Bladder

• The internal surface has folds of mucous membrane, except for the trigone of the bladder above and behind the internal urethral orifice.
• At the apex is the internal orifice of the urethra.
• At the base is the interureteric crest.
• At both ends of the base are the right and left ureteric orifices.

Bladder Structure

• Layers of Bladder structure include: Peritoneum, Muscular Layer and Mucous membrane.
• The Muscular layer, detrusor muscle has 3 layers: external longitudinal, middle circular(sphincter vesicae muscle at the internal urethral orifice, involuntary, innervated by the autonomic nervous system), and inner longitudinal.

Vessels, Nerves, and Lymphatics of the Bladder

• Arterial supply comes from the superior and inferior vesical arteries.
• The bladder's venous plexus drains into the internal iliac veins.
• Nerve supply: sympathetic nerves (lower 2 thoracic + upper 2 lumbar levels) and parasympathetic nerves (S2-4).
• Lymphatic drainage goes to the external iliac and common iliac nodes.

Male Urethra

• The male urethra is 15-20cm long.
• It extends from internal urethral orifice(urinary bladder) to external urethral orifice(at the tip of the penis).
• The male urethra has three parts: prostatic, membranous, and spongy(penile).

Prostatic Urethra

• The prostatic urethra traverses the prostate gland and is the widest part of the male urethra.
• It is 3cm long.
• On the posterior wall: urethral crest, prostatic sinus, seminal colliculus, prostatic utricle (vagina masculina), and openings of ejaculatory ducts.

Membranous Urethra

• The membranous part is the shortest, narrowest, and least dilatable part of the urethra, as it is 2cm long..
• It passes through the urogenital diaphragm.
• The membranous urethra is surrounded by the sphincter urethrae muscle (external urethral sphincter), is voluntary m., and innervated by pudental n.

Spongiose (Penile) Urethra

• The Spongiose Urethra is 15cm long.
• It is located in the corpus spongiosum of the penis.
• It is narrow (about 6mm in diameter).
• The most dilated parts include the intrabulbar fossa (at the commencement) and the navicular fossa (at the glans penis).
• The narrowest part is the external urethral orifice.
• Bulbourethral glands and other urethral glands open into the spongy part of the urethra.

Female Urethra

• The female urethra is 4-5cm long, 6mm wide, and much dilatable.
• It extends from internal urethral orifice(bladder) to external urethral orifice(anterior to the opening of vagina)
• It has two parts: pelvic and perineal.
• The epithelium contains longitudinal folds and a urethral crest.
• Contains urethral glands (homologous to the prostate) and minute recesses (lacunae) + paraurethral duct.

Sphincters of the Urethra

• Internal Sphincter, sphincter vesicae m. at beginning, internal urethral orifice, involunatry -nonstriated muscle and innervated by pelvic splanchnic nn.
• External Sphincter, sphincter urethrae muscle is at the urogenital diaphragm that is voluntary and striated muscle. It is innervated by pudental n.