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*15 pages explaining the entire feline endocrine system including : pituitary gland, parathyroid gland, thyroid
gland, kidney, adrenal glands, pancreas, hypothalamus, gastrointestinal (GI) tract, liver, ovaries and the testes
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There are also explanations about hormones – where they are secreted, what are their uses and why they are
important
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It plays a major role within the body affecting almost every organ and cell
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Hormones move throughout the body and are usually under the control of the pituitary gland based at the
bottom of the brain
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In order to keep a balanced amount of hormone being produced within the body,
the endocrine system relies on feedback given by interactions between the endocrine glands, the blood levels
of various hormones and the particular activities of the target organ
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Hypothalamus

Location – the Hypothalamus is found at the Base of the brain
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The Hypothalamus is to connect to the central nervous system via the
pituitary gland; it is also connected to areas of the autonomous nervous system
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The hypothalamus influences development within the body such as females exhibiting normal reproductive
activity and displaying the appropriate reproductive behaviours in adult life
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g different odours dependent on which sex the odour is released can stimulate different sexual behaviour
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The hypothalamus produces Releasing
Hormones within the hypothalamic nuclei which can be transported along axons to the median eminence or
the posterior pituitary to be stored and released as needed
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The hormones released
from the anterior pituitary are:


Thyrotropin-releasing hormone (TRH) produced by the parvocellular neurosecretory cells of the
paraventricular nucleus
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

Corticotrophin-releasing hormone (CRH) also produced from parvocellular neurosecretory cells of the
paraventricular nucleus stimulates Adrenocorticotrophic Hormone (ACTH) release
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

Growth-hormone-releasing hormone (GHRH) produced by the neuroendocrine neurons of the arcuate
nucleus and stimulates growth-hormone (GH) release
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Somatostatin (SS) produced by the neuroendocrine cells of the Periventricular nucleus which prevents
growth-hormone (GH) release and moderately prevents Thyroid-Stimulating Hormone (TSH) release
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Vasopressin (ADH) produced by the Magnocellular and Parvocellular neurosecretory cells of the
paraventricular nucleus and also produced by the Magnocellular cells in the supraoptic nucleus which
increases the permeability to water of the cells of distal tubule and collecting duct in the kidney and
thus allows water reabsorption and excretion of concentrated urine
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The
hypothalamus responds to light and seasonal systems such as daylight , Olfactory Stimuli (e
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smell),
autonomic inputs ( controls bodily functions largely unconsciously such as digestion, heart rate etc
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, stress and resetting body temperature
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The sense of smell helps with synchronization of oestrus and menstruation; a feline in heat is a good
example of this function
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Structure – the pituitary gland is an oval shaped gland, smaller than a pea
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The Adenohypophysis lobe produces a variety of hormones and is subdivided into three sections
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The neurohypophysis lobe is controlled by nerve fibres from the hypothalamus
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The Pituitary gland produces growth hormone which helps stimulate growth of multiple cells and tissues types
and creates ‘prolactin’ which stimulates mammary gland to produce milk especially after giving birth
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The pituitary gland can produce hormones that affect pigment called melanocytestimulating hormone (MSH) and the adrenocorticotrophic hormone (ACTH) which helps the adrenal gland to
produce cortisol
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Thyroid gland and the Parathyroid Gland

Thyroid Gland
Location - In the neck below larynx (voice box)
Structure – a long dark red vein of variable size dependent on breed
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It’s a gland that usually cannot be felt in the cat
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The thyroid tissue comprises mostly of follicular cells which are made of
millions of tiny saclike structures called follicles
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To regulate the body’s
metabolism, T4 and T3 are needed so iodine must available for the thyroid to be able to produce these
hormones
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Tissues within the body are stimulated by the T4 and T3
hormones to produce proteins and increase the amount of oxygen used by cells
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Parathyroid gland
Location –In the neck, beside or within the thyroid gland
Structure – There are 4 parathyroid glands situated in the neck of the feline with two parathyroid glands
closely associated to each thyroid lobe
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External parathyroid glands are smaller than the thyroid lobes – approx
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Function- the role that the Parathyroid gland primarily plays within the body is maintaining and regulating
calcium via the secretion of Parathyroid hormone (PTH) and Vitamin D working alongside the thyroid
hormone, Calcitonin
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Gastrointestinal (GI) Tract

Location – Found In the abdominal cavity that travels the length of the body
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Cell type, muscle thickness, glandular elements and nervous supply are all different in various
functional regions of the GI Tract; and also the shape and diameter of the tube varies
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The oesophagus runs from the neck (cervical), through the chest (thoracic) to the stomach
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In a feline it is 12-15 inches long and a
half inch in diameter when collapsed
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The outlet of the stomach leads into the small intestine, the outlet is called
the Pylorus
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The left side
of the stomach is larger than the right side and is called the Fundus
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The walls of the stomach contain muscles that move the food
along the body and the lining of the stomach contains glands that produce acids and enzymes that digest food
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The longest portion of the GI tract is the small intestine which is roughly three to four times longer than the
length of the feline’s body and is made of a circular hollow tube
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The small intestine consists of the duodenum, the
jejunum and ileum
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Function – The oesophagus within the GI Tract makes wavelike contractions called peristalsis to move food
from the mouth, down the neck, through the chest and into the stomach
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The stomach assists in the early stages of digestion and prepares food for further processing in the small
intestine
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Chemicals and enzymatic digestion happens also within the stomach,
most commonly protein
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Absorption of most nutrients into the blood happens within the small intestine
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The small intestine is
also in control of absorbing water, electrolytes and molecules
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The last phase of digestion happens within the large intestine the functions are; to recover last available water
and electrolytes from food, producing enzymes mixed with bacteria to break down hard-to-digest foods and to
form and store faeces
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Structure- The pancreas is situated towards in the craniodorsal part of the abdomen sitting closely to the
duodenum
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The lobes are
loosely attached via connective tissues which contain blood vessels, nerves and clear-fluid carrying lymphatics
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The tip of the
left lobe contacts the left kidney and lies in the greater Omentum (a long fold of visceral peritoneum hanging
down from the start of the stomach); which is the smallest lobe out of the two
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Within the pancreas there are two ducts; the pancreatic duct and the Accessory duct
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The Accessory duct is the minor duodenal papilla
and opens on the opposite side of the duodenum
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Function – The pancreas aids maintenance of the correct glucose (blood sugar) level using hormones it
produces and secretes into the bloodstream called Insulin and Glucagon
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The glucose then can be used
as energy for the cells or it can be stored within the liver via the hormone glucagon when glucose levels are
too high; and also stored in the muscles as glycogen
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The pancreas also helps with the digestion of protein and lipids (fats) by producing important protein-digesting
enzymes, Trypsin and Chymotrypsin and fat-digesting enzymes called Lipases which are produced within the
pancreas
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If
cats were without these enzymes, the body would not be able to break down important dietary constituents
and if the pancreas does not produce the suitable amounts of these enzymes it can lead to the condition called
Pancreatic Insufficiency
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Kidneys and the Adrenal Glands

Location – the kidneys are located in the front part of abdominal cavity under the backbone and close to
where the last rib meets the spine
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Structure – The kidneys are two bean-shaped organs joined together
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Function – The main functional element of the kidney is the nephron consisting of several microscopic filtering
units which are in control of removing urea; a combination of water and other waste products of metabolism
used to produce urine
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Urine is collected into a collecting chamber found in the middle of the kidney in the area of the Hilus,
once emptied into the pelvis
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The kidneys make sure the body tissues remain hydrated by monitoring and
balancing body water to enable them to function properly and remain healthy
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Regulating the acid-base balance (PH) of body fluids and the blood is another job
the kidneys take care of; rejecting or storing certain ions to help the body maintain optimum balance
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Erythropoietin is a hormone the kidneys secrete which stimulates the production of red blood cells from the
bone marrow
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Adrenal Glands
Location – located in the abdominal cavity directly in front of the kidneys
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The adrenal glands are
comprised of two separate endocrine organs; the outer section called the adrenal cortex and the inner section
called the adrenal medulla
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The adrenal cortex holds essential mineralocorticoids
such as the hormone Aldosterone that help regulate blood pressure and volume by holding on to sodium and

water that the body requires
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Adrenaline is produced by the other organ, the Adrenal Medulla
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The
hormone works by secreting when the feline is experience intense emotional stimuli such as stress, fear and
excitement
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Liver

Location- found in the Front of the abdomen, behind diaphragm and below the stomach
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The liver has several hepatic lobes that are joined together but hard
to distinguish between
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The liver is a strong, hardworking organ that can greatly increase its output and efficiency at
a moment’s notice as it has exceptional reserve capacities which can make the liver go into overdrive
especially when any of the four lobes are fighting bacterial or viral infection and diseases such as cancer to
make sure the body gets what it requires
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For some animals including felines, the liver has the ability to regenerate and still
be fully functional after overcoming damage
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The tissue that gets the first intake of
nutrients is the liver which is originally absorbed from the intestines and stomach; and every blood vessel from
the gastrointestinal tract goes to the liver too
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Angiotensin reacts to renin to Angiotensin-I, which is then converted to
Angiotensin-II in the lungs
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Ovaries

Location – the right and left ovaries are located behind the kidneys
Structure – Suspended from the top of the abdomen by a wide ligament called the suspensory ligament is how
the ovaries are placed
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A funnel –like structure called the infundibulum, is at the end of the oviduct nearest to the ovary; its
role being to collect the egg (Ovum) when it’s released from the ovary
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From each ovary an uterine horn extends and joins to form the body of the uterus
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Once fertilized the eggs are released from the follicles (a small sac-like
structure during the process of ovulation and then carries the eggs to through the fallopian tubes into the
uterus
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Oestrogen is produced from testosterone and the levels of oestrogen rise during feline heat cycles
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Progesterone stimulates the development of the mammary glands (breast tissue) and
works with oestrogen during the changes to breast tissue after puberty, during pregnancy and during nursing
to produce milk for babies
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)
Structure – There are two testes within the scrotum which are both round to oval shaped
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Sertoli cells support and give
nutrition to the sperm cells
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Maturation of sperm is stimulated by the production and release of both Follicle Stimulating
Hormone (FSH) and Testosterone
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For normal sperm production the testes
must descend into the scrotum as sperm cannot develop normally as the normal body temperature of the
feline is too high
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References: http://www
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net https://www
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