PANCREAS AND GONADS
PANCREAS-
The pancreas is an abdominal glandular organ with both digestive (exocrine)
and hormonal (endocrine) functions.
Anatomical Position
The pancreas is an oblong-shaped organ positioned at the level of the transpyloric plane (L1).
With the exception of the tail of the pancreas, it is a retroperitoneal organ, located deep within
the upper abdomen in the epigastrium and left hypochondrium regions.
Within the abdomen, the pancreas has direct anatomical relations to several structures
Organs:
Stomach Separated from the pancreas by the lesser sac, the stomach and pylorus lie anterior
and to the pancreas.
Duodenum The C shaped duodenum curves around and outlines the head of the pancreas.
The first part of the duodenum lies anteriorly whereas the second part of the duodenum including
the ampulla of Vater lies laterally to the right of the pancreatic head
Transverse mesocolon Attaches to the anterior surface of the pancreas
Common bile duct Descends behind the head of the pancreas before opening into the second
part of the duodenum alongside the major pancreatic duct through the major duodenal papilla
Spleen located posteriorly and laterally. The lienorenal ligament is formed from peritoneum
and connects the spleen to the tail of the pancreas.
Vessels
The pancreas lies near several major vessels and significant landmarks in vascular anatomy:
The aorta and inferior vena cava pass posteriorly to the head of the pancreas.
The superior mesenteric artery lies behind the neck of the pancreas and anterior to the uncinate
process.
Posterior to the neck of the pancreas, the splenic and superior mesenteric veins unite to form the
hepatic portal vein.
As it journeys from its origin at the celiac plexus to the splenic hilum, the splenic artery traverses
the superior border of the pancreas.
Anatomical Structure
The pancreas is typically divided into five parts:
Head the widest part of the pancreas. It lies within the C-shaped curve created by the
duodenum and is connected to it by connective tissue.
Uncinate process a projection arising from the lower part of the head and extending medially
to lie beneath the body of the pancreas. It lies posterior to the superior mesenteric vessels.
Neck located between the head and the body of the pancreas. It overlies the superior
mesenteric vessels which form a groove in its posterior aspect.
Body centrally located, crossing the midline of the human body to lie behind the stomach and
to the left of the superior mesenteric vessels.
Tail the left end of the pancreas that lies within close proximity to the hilum of the spleen. It is
contained within the splenorenal ligament with the splenic vessels. This is the only part of the
pancreas that is intraperitoneal.
The Duct System
The exocrine pancreas is classified as a lobulated, serous gland which produces digestive
enzyme precursors. It is composed of approximately one million berry-like clusters of cells
called acini, connected by short intercalated ducts.
The intercalated ducts unite with those draining adjacent lobules and drain into a network
of intralobular collecting ducts, which in turn drain into the main pancreatic duct.
The pancreatic duct runs the length of the pancreas and unites with the common bile duct,
forming the hepatopancreatic ampulla of Vater. This structure then opens into the duodenum
via the major duodenal papilla.
Secretions into the duodenum are controlled by a muscular valve the sphincter of
Oddi. It surrounds the ampulla of Vater, acting as a valve.
Vasculature
The pancreas is supplied by the pancreatic branches of the splenic artery. The head is
additionally supplied by the superior and inferior pancreaticoduodenal arteries which are
branches of the gastroduodenal (from coeliac trunk) and superior mesenteric arteries,
respectively.
Venous drainage of the head of the pancreas is into the superior mesenteric branches of
the hepatic portal vein. The pancreatic veins draining the rest of the pancreas do so via
the splenic vein.
Lymphatics
The pancreas is drained by lymphatic vessels that follow the arterial supply. They empty into
the pancreaticosplenal nodes and the pyloric nodes, which in turn drain into the superior
mesenteric and coeliac lymph nodes.
GONADS
Gonads are the female and male reproductive organs. Testes are the male gonads and ovaries in
females. These reproductive organs are essential for sexual reproduction since they are
responsible for the production of male and female gametes. Gonads are also responsible for
producing sex hormones required for the development and growth of primary and secondary
sexual characteristics.
Gonads: Sex Hormones
Being a component of Endocrine system, both male and female gonads generate sex hormones.
The sex hormones are steroid hormones and can pass through the cell membrane of their target
cells. Gonadal hormones are regulated by hormones secreted by the pituitary gland in the brain.
Hormones that are responsible for stimulating the gonads to produce sex hormones are called
gonadotropins. The gonadotropins called luteinizing hormone (LH) and follicle-stimulating
hormone (FSH) are secreted by the pituitary.
The pituitary hormones influence reproductive organs in many ways.
The tests are stimulated by the LH to secrete the sex hormone testosterone and ovaries to secrete
estrogens and progesterone. The FSH is involved in the maturation of ovarian follicles (sacs that
contain ova) in females and production of sperm in males.
Female Gonad Hormones
The major hormones of the ovaries are progesterone and estrogens.
Estrogens It is a group of female sex hormones essential for reproduction and the development
of the female reproductive system. Estrogens are responsible for maturation and growth of the
vagina and uterus, widening of pelvis, breast and the uterus changes during the menstrual cycle,
and increasing growth of hairs on the body.
Progesterone These are the hormones whose function is to prepare the uterus for conception,
regulating changes in the uterus during the Menstrual cycle, ovulation aids, and stimulating
gland development for the production of milk during pregnancy.
Male Gonad Hormones
Androgens are hormones that majorly influence the development of the male reproductive
system.
Testosterone is responsible and essential for increased growth of bone and muscle, growth of
body hair, developing broader shoulder, voice deepening and growth of the penis.
Androstenedione These are the hormones that act as a precursor to estrogens and testosterone.
Inhibin These hormones inhibit the release of FSH and thought to be involved in sperm cell
regulation and development.