BSC 215 Lecture Notes - Lecture 55: Internal Sphincter Muscle Of Urethra, Renal Artery, Renal Pyramids
11 Jun 2018
School
Department
Course
Professor
Ureters
The ureters, one from each kidney, deliver urine to the urinary bladder. The ureters
enter through the back of the urinary bladder, entering at an angle such that when the
urinary bladder fills, the ureter openings are forced closed. A cross section of the ureter
reveals three layers of tissue:
• An inner mucosa consists of transitional epithelium covered by a lamina propria
of connective tissue. Mucus secretions protect the ureter tissues from the urine.
• A middle muscularis layer consists of longitudinal and circular layers of smooth
muscle fibers. The muscle fibers force urine forward by peristalsis.
• The outer adventitia consists of areolar connective tissue containing nerves,
blood vessels, and lymphatic vessels.
Urinary Bladder
The urinary bladder is a muscular sac for storing urine. The triangular base of the
urinary bladder, the trigone, is defined by the two ureters that deliver the urine and the
one urethra that drains the urine. When empty, the urinary bladder collapses and
develops folds (called rugae) within the urinary bladder wall. As it fills, the folds become
distended and the urinary bladder becomes spherical (smooth on the inside). The wall
of the urinary bladder consists of three layers similar to those of the urethra: the
mucosa, the muscularis (here called the detrusor muscle), and the adventitia. Circular
smooth muscle fibers around the urethra form the internal urethral sphincter.
Anatomy of the Kidneys
Understanding how the urinary system helps maintain homeostasis by removing
harmful substances from the blood and regulating water balance in the body is an
important part of physiology. Your kidneys, which are the main part of the urinary
system, are made up of millions of nephrons that act as individual filtering units and are
complex structures themselves. The ureters, urethra, and urinary bladder complete this
intricate system.
The urinary system helps maintain homeostasis by regulating water balance and by
removing harmful substances from the blood. The blood is filtered by two kidneys, which
produce urine, a fluid containing toxic substances and waste products. From each
kidney, the urine flows through a tube, the ureter, to the urinary bladder, where it is
stored until it is expelled from the body through another tube, the urethra.
The kidneys are surrounded by three layers of tissue:
• The renal fascia is a thin, outer layer of fibrous connective tissue that surrounds
each kidney (and the attached adrenal gland) and fastens it to surrounding
structures.
find more resources at oneclass.com
find more resources at oneclass.com
• The adipose capsule is a middle layer of adipose (fat) tissue that cushions the
kidneys.
• The renal capsule is an inner fibrous membrane that prevents the entrance of
infections.
Inside the kidney, three major regions are distinguished, as shown in Figure 1:
• The renal cortex borders the convex side.
• The renal medulla lies adjacent to the renal cortex. It consists of striated, cone‐
shaped regions called renal pyramids (medullary pyramids), whose peaks, called
renal papillae, face inward. The unstriated regions between the renal pyramids
are called renal columns.
• The renal sinus is a cavity that lies adjacent to the renal medulla. The other side
of the renal sinus, bordering the concave surface of the kidney, opens to the
outside through the renal hilus. The ureter, nerves, and blood and lymphatic
vessels enter the kidney on the concave surface through the renal hilus. The
renal sinus houses the renal pelvis, a funnel‐shaped structure that merges with
the ureter.
Blood and nerve supply
Because the major function of the kidneys is to filter the blood, a rich blood supply is
delivered by the large renal arteries. The renal artery for each kidney enters the renal
hilus and successively branches into segmental arteries and then into interlobar
arteries, which pass between the renal pyramids toward the renal cortex. The interlobar
arteries then branch into the arcuate arteries, which curve as they pass along the
junction of the renal medulla and cortex. Branches of the arcuate arteries, called
interlobular arteries, penetrate the renal cortex, where they again branch into afferent
arterioles, which enter the filtering mechanisms, or glomeruli, of the nephrons.
Figure 1. (a) The urinary system, (b) the kidney, (c) cortical nephron, and (d)
juxtamedullary nephron of the kidneys.
find more resources at oneclass.com
find more resources at oneclass.com
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The ureters, one from each kidney, deliver urine to the urinary bladder. The ureters enter through the back of the urinary bladder, entering at an angle such that when the urinary bladder fills, the ureter openings are forced closed. A cross section of the ureter reveals three layers of tissue: an inner mucosa consists of transitional epithelium covered by a lamina propria of connective tissue. Mucus secretions protect the ureter tissues from the urine: a middle muscularis layer consists of longitudinal and circular layers of smooth muscle fibers. The muscle fibers force urine forward by peristalsis: the outer adventitia consists of areolar connective tissue containing nerves, blood vessels, and lymphatic vessels. The urinary bladder is a muscular sac for storing urine. The triangular base of the urinary bladder, the trigone, is defined by the two ureters that deliver the urine and the one urethra that drains the urine.
