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.