Chapter 17 : Endocrine System Flashcards
Endocrine system
Uses glands, tissues, and cells to produce molecules called hormones
These hormones will control the bodies metabolism, growth and development
Endocrinology
The study of the endocrine system and the diagnosis and treatment of its disorders
Endocrine glands
An organ that produces the hormone
Hormones
Chemical messengers that are transported by the bloodstream and stimulate physiological responses in cells of another tissue or organ, often a considerable distance away
Overview of cell communications
Internal communication is necessary for coordination of cell activities
There are 4 principle mechanisms of communication between cells
- gap junctions, neurotransmitters, paracrine hormones, and hormones
Gap junctions
Pores in cell membrane allow signaling molecules, nutrients, and electrolytes to move from cell to cell
Paracrine ( local ) hormones
Secreted into tissue fluids to affect nearby cells
What is this organ from the endocrine system?
Pineal gland
What is this organ from the endocrine system?
Hypothalamus
What is this organ from the endocrine system?
Pituitary gland
What is this organ from the endocrine system?
Thyroid gland
What is this organ from the endocrine system?
Thymus
What is this organ from the endocrine system?
Adrenal gland
What is this organ from the endocrine system?
Pancreas
What is this organ from the endocrine system?
Parathyroid glands
What is this organ from the endocrine system?
Gonads: ovary (female)
What is this organ from the endocrine system?
Gonads: testis (male)
Communication by the endocrine system compared to the nervous system
Response take longer before they begin and last longer
Works with the nervous system via the adrenal gland and pituitary gland
Communication of the endocrine system
Body tells endocrine gland to release its hormones into a capillary bed
They travel around the body until they reach the target cells
Target cell then does what it was told to do by that hormone
Target cells
A Cell that has a receptor for that specific hormone
Anterior pituitary gland
Controlled by hormones from the hypothalamus via a portal system
Far more vascularized (darker color)
More cellular
Portal system
2 subsequent capillary beds
Posterior pituitary gland
Hypothalamus has neurons that travel to the posterior pituitary gland
Less cellular and has many nerve fibers  (has lighter stain)
Hypophyseal portal system: hypothalamic hormones
Hypothalamic releasing and inhibiting hormones travel in hypophyseal portal system from hypothalamus to anterior pituitary gland
Hypophyseal portal system: anterior lobe hormones
Hormones secreted by anterior pituitary gland
Chromophobe
In the anterior pituitary gland
Don’t stain very dark
Chromo-color
Phobe/phobia-aversion to something/don’t like it
Acidophil
Darker stain
TRH
Thyroid releasing hormone
Tells anterior pituitary gland to direct hormones to the thyroid
Releasing hormones
The hormones the hypothalamus makes to direct the pituitary gland to release hormones
GnRH
Gonad releasing hormone
Tells anterior pituitary gland to direct hormones to the gonads
CRH
Corticotropin releasing hormone
Directs anterior pituitary gland to direct hormone to adrenal gland
GHRH
Growth hormone releasing hormone
Directs anterior pituitary gland to produce growth hormone
PRL
Prolactin
Anterior pituitary gland produces it
Tells mammary gland to begin producing lactin
After birth stimulates mammary glands to synthesize milk, enhances secretion of testosterone by testes
TSH
Thyroid stimulating hormone
Produced by the anterior pituitary gland
Stimulates secretion of thyroid hormone
LH
Luteinizing hormone
Produces by anterior pituitary gland
Direct gonads
Stimulates ovulation, corpus luteum to secret progesterone, and stimulates testes to secret testosterone
FSH
Follicle stimulating hormone
Produced by anterior pituitary gland
Directs gonads
Stimulates secretion of ovarian sex hormones, development of ovarian follicles, and sperm production
GH
Growth hormone
Produced by anterior pituitary gland
Active most importantly on liver and muscle cells
Stimulates mitosis and cellular differentiation
ACTH
Adrenocorticotropin hormone
Produced by anterior pituitary gland
Works on the adrenal cortex to secret glucocorticoids
Neurohyphothesis
Neurons that pass down into the posterior pituitary gland
ADH
Antidiuretic hormone
Produced by posterior pituitary gland and Directs the kidneys
Increases water retention thus reducing urine volume and prevents dehydration
Also called vasopressin because it can cause vasoconstriction
OT
Oxytocin hormone
Produced by posterior pituitary gland
Directs uterus to increase uteri contractions and increases the frequency of contractions
Posterior pituitary hormones
Produced in hypothalamus
Transported by hypothalamus- hypophyseal tract to posterior lobe
Releases hormones when hypothalamic neurons are stimulated
Endocrine secretion is typically controlled by….
Negative feedback mechanisms
Negative feedback
Increased target organ hormone levels inhibits release of hormones
Positive feedback
Stretching of uterus increases OT release, causes contractions, causing more stretching of uterus, etc. Until delivery
Thymus
Has roles in 3 systems:endocrine, lymphatic, and immune
Sale of maturation of T cells important in immune defense
Secretes thymopoietin, thymosin, and thymolin which stimulates development of other lymphatic organs and activity of T-lymphocytes
Thyroid gland
Largest endocrine gland
Composed of 2 lobes and an isthmus below the larynx
Has a dark reddish brown cover due to rich blood supply
Thyroid follicles
Sacs that compose most of thyroid
Contain protein rich colloid
Follicular cells
Simple cuboidal epithelium that lines follicles
Thyroxine (T4) and triiodothyronine (T3)
Thyroid hormone that increases metabolic rate, O2 consumption, heat production, appetite, growth hormone secretion, alertness and quicker reflexes
Parafollicular (C or clear) cells
Secrete calcitonin with rising blood calcium
Stimulates osteoblasts activity and bone formation
Colloid
Stores thyroid hormone
Helps thyroid dissolve and stores to release the hormone quickly
Parathyroid glands
Usually four glands partially embedded in posterior surface of thyroid gland
Can be found from as high as hyoid bone to as low as aortic arch
Parathyroid hormone (PTH)
Secreted parathyroid glands
Increases blood Ca^2+ (calcium ion) ‘ levels
Promotes synthesis of calcitriol
Increases absorption of Ca^2+
Decreases urinary excretion
Increases bone resorption
Histology of parathyroid glands
Adrenal gland
-Small grand that sits on top of each kidney
-They are retroperitoneal like the kidney
-Has an adrenal cortex and medulla formed by 2 fetal stands with different origins and functions
What is this feature of the adrenal gland?
Connective tissue capsule
What is this feature of the adrenal gland?
Adrenal cortex
What is this feature of the adrenal gland?
Adrenal medulla
What is this feature of the adrenal gland?
Zona glomerulosa
What is this feature of the adrenal gland?
Zona fasciculata
What is this feature of the adrenal gland?
Zona reticularis
Adrenal cortex
Surrounds adrenal medulla and produces more than 25 steroids hormones called corticosteroids or corticoids
Zona glomerulosa (thin, outer layer of adrenal cortex)
Cells are arranged in rounded clusters
Secretes mineralocorticoid: regulate the body’s electrolyte balance
Zona fasciculata (thick, middle layer of adrenal cortex)
Cells arranged in fascicles separated by capillaries
Secretes glucocorticoids
Zona reticularis (narrow, inner layer of adrenal cortex)
Cells in branching network
Secretes sex steroids
Pancreatic hormones: insulin
Secreted during and after meals when glucose and amino acid blood levels are rising
Stimulates cells to absorb nutrients and store or metabolize them which lowers blood glucose levels
A negative feedback mechanism
Diabetes mellitus
Causes insufficiency or inaction of insulin
Pancreatic hormones: glucagon
-Secreted by A alpha cells
-Released between meals when blood glucose concentration is failing
-In liver, stimulates gluconeogenesis, glycogenolysis, and the release of glucose into the circulation raising blood glucose revels
-In adipose tissue, stimulates fat catabolism and release of free fatty acids
Pancreatic hormones: somatostatin
Secreted by D or delta cells
Partially suppresses secretion of glucagon and insulin
Inhibits nutrients digestion and absorption which prolongs absorption of nutrients
Pancreatic hormones: pancreatic polypeptide
Secreted by pp cells or F cells
Inhibits gallbladder contraction and secretion of pancreatic digestive enzymes
Pancreatic hormones: gastrin
Secreted by G cells
Stimulates stomach acid secretion, motility and emptying
Pancreas info
Endocrine function: controlled by pancreatic islets
Exocrine function: controlled by exocrine acinus
Found retroperitoneal and is inferior and posterior to the stomach
Glucagon
Also released to rising amino acid levels in blood, promotes amino acid absorption, and provides cells with raw material for gluconeogenesis
Blood glucose homeostasis when Blood glucose increases: step 1
Blood glucose increases → beta islet cells sense it and begin to secrete insulin → all cells are stimulated to tale up glucose for future use
Blood glucose homeostasis Blood glucose increases: step 2
The liver and muscle take up glucose and store it us glycogen
Blood glucose homeostasis Blood glucose increases: step 3
Adipose tissue take up lipids and store them as triglycerides
Blood glucose homeostasis when glucose decreases: step 1
Blood glucose levels decrease → alpha cells produce and secrete glucagon→glucagon targets the liver and the liver breaks down glycogen and secretes glucose into the blood → brings blood glucose levels up
Blood glucose homeostasis when glucose decreases: step 2
Adipose tissue releases stored lipids (as HDL’s) and the liver then takes up that fat and catabolizes it using the energy to produce new glucose →brings down blood glucose levels back to homeostasis
Diabetes mellitus
Most prevalent metabolic disease in the world
Disruption of metabolism due to hyposecretion or inaction of insulin
Symptoms revealed by elevated blood glucose, glucose in urine and ketones in the urine
Transport maximum
Limit to how fast the glucose transporters can work to reabsorb
Excess glucose enters urine and water follows it
Causes polyuria, dehydration,and thirst
Type 1 diabetes mellitus
5-10 % of cases in the US
Insulin is always used to treat
Hereditary susceptibility if infected with certain viruses (rubella, cytomegalovirus)
Autoantibodies attack and destroy pancreatic beta lens
Type 2 diabetes mellitus
90- 95% of cases
Problem is insulin resistance: failure of target cells to respond to insulin
Treated with weight loss program and exercise or oral medications
Pathogenesis
Cells can’t absorb glucose, must very on fat and proteins for energy needs
Fat catabolism increases free fatty acids and ketones in blood
Ketonuria
Promotes osmotic diuresis, loss of sodium and potassium, irregular heartbeat, and neurological issues
Ketoacidosis
Occurs as ketones decrease blood pH
Deep, gasping breathing and diabetic coma are terminal result
Chronic pathology (chronic hyperglycemias)
Leads to neuropathy and cardiovascular damage from atherosclerosis and microrascular disease
Arterial damage in retina and kidneys (common in type 1)
Atherosclerosis leads to heart failure (common in type 2)
Diabetic neuropathy
Nerve damage from impoverished blood flow can lead to erectile dysfunction, incontinence, poor wound healing, and loss of sensation from even
Normal blood glucose level
70-120 mg/dl
The gonads
Ovaries and testes are both endocrine and exocrine
Exocrine product
Whole cells - eggs and sperm ( cytogenic glands)
Endocrine product
Gonadal hormones - mostly steroids
Ovarian hormones
Estradiol, progesterone, and inhibin
Estrogen and progesterone produce the female characteristics
Testicular hormones
Testosterone, weaker androgens, estrogen and inhibin
Testosterone will produce masculine characteristics
Hormone clearance
Hormone signals must be turned off when they have served their purpose
Most hormones are taken up and degraded by liver and kidney (excreted in bile or urine)
Metabolic clearance rate (MCR)
Rate of hormone removal from the blood
Half-life: time required to clear 50% of hormone from the blood
Faster the MCF, the shorter is the half-life
