The Endocrinal System Flashcards
What is the endocrinal system?
The endocrinal system is a collection of glands from around the body
What are glands responsible for?
Glands are responsible for manufacturing, storing and releasing at least 1 specific molecule called a ‘hormone’ (A “chemical messenger”)
What are hormones involved in?
Hormones are involved in regulating:
Metabolism
Growth
Reproductive function (inc. Pregnancy)
Body’s stress response
What processes do hormones control?
Hormones control processes that require duration of action (length) rather than speed of action which is provided by the nervous system.
e.g
Blood hormones levels must be controlled (within ‘normal range’) for homeostasis
Hormones are released into the blood stream and transported to cells distant from the source.
Why is homeostasis important?
The body’s physiological parameters are (and must be) kept relatively constant (within the “normal ranges”) despite opposing external influences:
“normal ranges”:
Temperature (36.8 C.)
Pulse (70bpm)
pH (7.4)
Arterial PO2 (>95%)
Blood Glucose (4-8mmol/L)
What are the homeostasis paramaeters necessary for and how is homeostasis maintained?
These conditions are necessary for normal cellular function (or else organs and tissues stop working properly)
Maintenance of homeostasis is by “negative feedback”
The activity of hormones is almost always controlled by negative feedback mechanisms
What are the Hormonal Secretion patterns?
Hormonal Secretion Patterns
Hormone A
Diurnal Secretion Pattern
Predictable over a 24-hour period
Hormone B
Constant secretion pattern
Maintenance of physiology function at all times
Hormone C
Episodic Secretion Pattern
-Reacts to a specific stimulus and less predictable.
how can the negative feedback mechanism be affected
The Target Cells sensitivity to the hormone may change
Tumour may be: “functioning” - too much hormone secreted.
Or non functioning - tumour destroys gland and too little hormone secreted
What can arise from hypersecretion/hyposecretion?
Clincal problems can arise from:
Hypersecretion of a hormone (too much)
Hyposecretion of a hormone (too little)
What endocrine glands exist in the body?
Head:
Hypothalamus
Pituitary gland
Neck:
4 Parathyroid glands
Thyroid gland
Abdomen:
2 adrenal glands
Pancreas
Pelvis (female):
2 Ovaries
Perineum (male):
2 testes
What is the diencephalon?
Diencephalon forms the central core of the cerebrum with connections to the right and left cerebral hemispheres and the midbrain.
Where is the Diencephalon, hypothalamus and brainstem located?
What parts does the brainstem consist of?
Brainstem:
Midbrain
Pons
Medulla
What is the pituitary gland divided into?
The pituitary gland is anatomically and functionally divided into the anterior pituitary and the posterior lobes
It lies in hypophyseal fossa of sphenoid bone.
What are Master glands?
They are hormones secreted from the pituitary control output of many other endocrine glands
What do the right and left temporal bone contain?
The right and left temporal bone contains organs of hearing and balance.
What is the function of the posterior pituitary gland?
Function of the Posterior Pituitary Gland
Also called ‘neurohypophysis’
Continuation of the hypothalamus
Axons project down through infundibulum to posterior pituitary.
Manufactures two hormones:
Oxytocin
Ejection of breast Milk
Stimulates uterine contraction in childbirth
Social Bonding
Vasopressin (ADH or antidiuretic hormone)
Aid water retention
What is a portal system?
Two venous capillary beds joined by a portal vein.
What is the functions of the hypothalamus and anterior pituitary gland?
Step 1
Hypothalamic Neurons secrete either:
Releasing hormones
Stimulate the anterior pituitary to release its hormone(s) into the bloodstream
Release-inhibitory hormones
Prevent the anterior pituitary releasing hormone(s) into the bloodstream.
Step 2:
Anterior pituitary cells secrete either:
Growth hormones (GH)
Prolactin (Milk production)
Thyroid stimulating hormone (TSH)
Adrenocorticotrophic Hormone (ACTH)
Luteinising Hormone (LH)
Follicle Stimulating Hormone (FSH)
What does the Thyroid gland manufacture and regulate?
Thyroid Gland
The Thyroid gland uses iodine to manufacture the 2 hormones:
Triiodothyronine (T3)
Thyroxine (T4)
Thyroid hormones regulate metabolism and stimulate growth.
What is the importance of Triiodothyronine, (T3)?
We cannot live without T3
Dietary lack of iodine is one cause of an enlarged (swollen) thyroid gland. An enlarged thyroid gland is called a “goitre”.
What are the parts in the context of the thyroid gland and parathyroid glands?
Epiglottis
Hyoid Bone
Thyroid cartilage
Cricoid cartillage
Right + left lobe
Isthmus
Trachea
What do parathyroid glands do and what are the features of PTH?
Parathyroid Glands manufacture and secrete parathyroid hormone
PTH controls the amount of calcium in blood and bone
PTH is not under pituitary control (the glands monitor blood CA++ and respond directly
What does normal muscle and nerve function depend on?
Normal Muscle and nerve function depends on blood Ca++ levels being in the normal range.
There are left and right parathyroid glands.
How is thyroid and parathyroid glands supplied with blood, and drained?
The Right inferior thyroid artery and left superior thyroid artery, alongside the aortic arch branches which provide blood for head, neck and upper limbs supply blood.
The right superior, middle and inferior thyroid veins join up with the superior vena cava
These veins drain blood from head neck and upper limbs.
What are the characteristics of the Pancreas?
Pancreas
Not under the control of the pituitary gland
It has 2 anatomically and functionally distinct parts:
The endocrine pancreas manufactures various hormones:
Insulin is secreted into the blood in responose to islet of Langerhans cells
Islet of Langerhans cells - contain beta cells that produce insulin
The exocrine pancreas manufactures enzymes and secretes them via a duct system into the duodenum
What are the two types of diabetes mellitus?
Diabetes Mellitus
Type 1 - failure to produce insulin
Type 2 - Target cells fail to respond to insulin.
Where is the pancreas?
Retroperitoneum
Overlying L1/L2 Vertebra
Posterior to stomach
Anterior to aorta and inferior vena cava
Between duodenum and spleen
How is blood supplied to the pancreas?
Arterial blood supply from both:
Coeliac trunk
Superior mesentric artery
How is blood drained from the pancreas?
Venous blood drains into both:
Splenic vein
Superior mesentric
Then into the portal vein
Where is the adrenal glands located?
Adrenal Glands are located:
Retroperitoneal
Superior to kidneys
Separated from kidney by a fascial septum
What anatomical and functional parts secrete hormones?
Adrenals cortex:
Glucocorticoids (under pituitary control)
Mineralocorticoids
Andorgens
Adrenal Medulla (fight or flight)
Adrenaline
Noradrenaline
What is the “fight” or “flight” response?
What is the “fight or flight” response?
Fear or serious illness or injury
I
Sympathetic division of the nervous system
I
The body’s organs and arterioles react in a “self-preservation” manner
I
The reaction includes stimulation of the adrenal medulla to secrete adrenaline and noradrenaline into the bloodstream.
How is blood supplied to the adrenal glands?
The same arteries are present on the right side
Left superior suprarenal arteries
Left middle Suprarenal artery (branch of the aorta)
Left inferior suprarenal artery (branch of the renal artery)
How is blood drained from the adrenal glands?
Blood is drained via the right and left suprarenal vein, which drains directly into the right and left renal vein respectively.
What are gonads?
Gonads are the part/organ of the reproductive system that produces and releases eggs (ovary) or sperm (testicles)
Where are the testes located?
Testes
Located in the scrotum of the male perineum
Arterial supply (Testicular artery) from abdominal aorta
Secretes testosterone in response to luteinising hormone from the anterior pituitary
What does testosterone control?
Testosterone controls:
Male secondary sex characteristics
Closure of epiphyseal growth plates
Stimulates sperm production
What parts are in contact with the testes?
Gonadal artery and veins
Gonadal artery and veins
(testicular a. And v.)
Scrotum
Where are the ovaries located?
Lies in pelvic cavity
Secretes oestrogen and progesterone in response to follicular stimulating hormone and luteinising hormone from the anterior pituitary.
Progesterone prepares the uterus for pregnancy
What does Oestrogen control?
Oestrogen controls:
Female secondary sex characteristics
Ovum Development
What parts are involved in the ovaries?
Gonadal artery and veins (Ovarian a. And v.)
Uterus
Ovary
Broad ligament of the uterus - parietal peritoneum
How is blood supplied to the gonads?
Blood is supplied to the gonads via the gonadal arteries (paired branches of the abdominal aorta)
How is blood drained from the gonads?
Blood is drained via the:
Right gonad directly into the IVC (Inferior Vena Cava)
Left gonad into the left renal vein
