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Endocrine System. Glands and Hormones. Definitions. Hormones are chemicals regulators, secreted into the blood, that affect the functioning of other cells These “other cells” are called target cells

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Endocrine system

Endocrine System

Glands and Hormones


  • Hormones are chemicals regulators, secreted into the blood, that affect the functioning of other cells

  • These “other cells” are called target cells

  • Hormones are specific for certain targets because hormones bind to specific receptors of target cells

Hormones regulate
Hormones Regulate

  • Growth

  • Metabolism

  • Fluid and electrolyte

  • Acid-base balance

  • Reproduction

  • Blood pressure

Endocrine glands and tissues
Endocrine Glands and Tissues

  • Secrete hormones Examples

    • Pituitary gland (hypophysis)

    • Thyroid gland

    • Parathyroid glands

    • Adrenal glands

    • Pancreas

    • Gonads

    • Endocrine tissues within other organs

Chemistry of hormones
Chemistry of hormones

  • Compounds that act as hormones are:

    • Steroids (derived from cholesterol)

    • Amines (derived from a single amino acid)

    • Peptides (smaller chains of amino acids)

    • Proteins (polypeptide chains of amino acids)

    • Glycoproteins (protein/carbohydrate complex)

Hormone secretion
Hormone Secretion




Hormone secretion




Target cell

Control of secretion
Control of Secretion

  • Negative feed back

    • Stimulus is decreased or inhibited by some factor such as concentration of hormone

    • Attempts to maintain normal levels of secretion

  • Positive feed back

    • Stimulus for secretion is increased or exaggerated

Pituitary gland hypophysis
Pituitary Gland (Hypophysis)

  • Small gland connected to hypothalamus

  • Two parts

    • Anterior pituitary (adenohypophysis)

    • Posterior pituitary (neurohypophysis)



posterior pituitary---------

-------anterior pituitary

Pituitary gland
Pituitary Gland

  • Posterior pituitary derived from neural brain tissue and connects to hypothalamus by the stalk-like hypothalamic hypophyseal tract

  • Anterior pituitary from ectodermal tissue in the roof of embryonic mouth.


Pituitary gland1
Pituitary Gland

  • Posterior pituitary secretes two hormones

    • Hormones produced by hypothalamus and placed in posterior pituitary for secretion

  • Anterior pituitary largest part

    • Produces and secretes most of the hormones

    • Under direct control of hypothalamus

      • Hypothalamus secretes releasing and inhibiting hormones that reach anterior pituitary through hypophyseal portal circulation.

Hormones of the posterior pituitary
Hormones of the Posterior Pituitary

  • Oxytocin (OT)

    • Target tissues are smooth muscles of reproductive system of both sexes

    • Actions in female

      • Labor (uterine) contractions

      • Release of milk from mammary glands (milk letdown)

    • Actions in male

      • Contraction of smooth muscle in reproductive tissue

Hormones of posterior pituitary
Hormones of Posterior Pituitary

  • Antidiuretic Hormone (ADH) (vasopressin)

    • Target tissues are kidneys, sweat glands and arterioles

    • Actions

      • Causes kidneys and sweat glands to conserve water

      • Causes vasoconstriction of arterioles

Hormones of anterior pituitary
Hormones of Anterior Pituitary

  • Human Growth Hormone (hGH)

    • Targets all cells especially skeletal and muscle tissue

    • Actions

      • Promotes secretion of insulin-like growth factors (IGFs) within target tissues

      • IGFs increase: -rate of cell division for growth

        -protein synthesis needed for growth

        -use of fat for energy

      • Results in growth to adulthood and maintenance of skeleton and muscles in adults

Hormones of the anterior pituitary
Hormones of the Anterior Pituitary

Human Growth Hormone Imbalances

  • Pituitary dwarfism caused by hyposecretion in children and adolescents resulting in small body

  • Giantism caused by hypersecretion in infants and children resulting in height of over 8 feet

  • Acromegaly caused by hypersecretion in adults resulting in distorted facial features

Hormones of anterior pituitary1
Hormones of Anterior Pituitary

  • Thyroid stimulating hormone (TSH)

    • Targets thyroid gland

    • Stimulates secretion of the thyroid hormones

  • Adrenocorticotropic Hormone (ACTH)

    • Targets Adrenal cortex

    • Stimulates secretion of glucocorticoids from adrenal glands

Hormones of anterior pituitary2
Hormones of Anterior Pituitary

  • Prolactin (PRL)

    • Targets mammary glands

    • Stimulates milk production in mammary glands in concert with other hormones

  • Gonadotropins

    • Follicle Stimulating Hormone (FSH) and

    • Luteinizing Hormone (LH)

    • Target the ovaries and testes (gonads)

    • Control female and male reproductive physiology

Control of secretion of anterior pituitary hormones
Control of Secretion of Anterior Pituitary Hormones

  • Secretion Stimulated by releasing hormones (RH’s) from hypothalamus through hypophyseal portal system

  • Secretion suppressed by inhibiting hormones (IH’s) from hypothalamus through hypophyseal portal system

  • All controlled by negative feedback

Thyroid gland
Thyroid Gland

  • Large butterfly-shaped gland in neck below voice box (larynx)

  • Has Two lobes connected by an isthmus

--------left lobe

right lobe-----


thyroid follicle-----

Histology of thyroid
Histology of Thyroid

  • Composed of many follicles filled with jelly-like (colloidal) thyroglobulin protein

  • Thyroid hormones T3 and T4 synthesized by follicle cells and stored in combination with thyroglobulin

Thyroglobulin with T3 and T4

Thyroid hormones
Thyroid Hormones

  • T3 short for triiodothyronine

  • T4 short for tetraiodothyronine (thyroxine)

Thyroid hormones1
Thyroid Hormones

  • Formed by addition of iodine to the thryroglobulin

  • 3 & 4 stands for number of iodines

Secretion of t 3 t 4
Secretion of T3 & T4

  • Synthesis and secretion stimulated by anterior pituitary hormone TSH

  • Portion of stored thyroglobulin taken in from colloid by follicles cells

  • Colloid digested by lysosomes releasing T3 & T4

  • T3 & T4 enter blood, combine with transport proteins and are transported to target cells

Synthesis and secretion of t 3 t 4 figure 18 11 in text
Synthesis and Secretion of T3 & T4 Figure 18.11 in text

Target cells and actions of t 3 t 4
Target Cells and Actions of T3 & T4

  • Actions

    • ATP production by mitochondria (aerobic cell respiration)

    • Normal growth

  • Control by negative feedback

Thyroid and negative feedback
Thyroid and Negative Feedback

  • Increase in blood levels of T3 & T4 etc.

  • Release of thyrotropin releasing hormone (TRH) inhibited

  • Release of thyroid stimulating hormone (TSH) inhibited

  • Secretion of T3 & T4 decreases

Imbalances of t 3 t 4
Imbalances of T3 & T4

  • Thyroid dwarfism (Cretinism)

    • Too little secretion of thyroid hormones during fetal development and infancy.

    • Severe forms of mental and physical retardation in the newborn.

    • Retardation is reversible if hormonal replacement therapy is started during the first four months of life.

Imbalances of t 3 t 41
Imbalances of T3 & T4

  • Hypothyroidism (in adults)

    • Too little T3 & T4

    • Symptoms

      • MR

      • bradycardia

      • BT

      • lethargy

      • goiter

      • weight gain

      • cold intolerance

      • myxedema

Imbalances of t 3 t 42
Imbalances of T3 & T4

  • Hyperthyroidism (in adults)

    • Too much T3 & T4

    • Grave’s disease most common form

    • Symptoms

      • MR

      • tachycardia

      • BT

      • anxiety & irritability

      • goiter

      • Exophthalmia (exophthalmos)

      • heat intolerance

      • weight loss

Imbalances of t 3 t 43
Imbalances of T3 & T4

  • Endemic goiter and iodine deficiency

    • Insufficient dietary iodine to make T3 & T4

    • Endemic means localized or regional

    • Lack of negative feedback from T3 & T4 causes over stimulation and overgrowth of the thyroid gland.

    • Goiter results (enlarged thyroid gland)

Thyroid disorders
Thyroid Disorders


Endemic Goiter

Control of blood calcium
Control of Blood Calcium

  • Calcitonin (CT) from thyroid lowers blood calcium by adding it to bones

  • Parathyroid hormone from parathyroid glands (small pea-shaped gland embedded in back of thyroid) increases blood calcium by removing it from bones

Adrenal glands
Adrenal Glands

  • Located on top of kidneys

  • Gross Anatomy

    • Enclosed by capsule

    • Outer cortex

    • Inner medulla

Histology of adrenal glands
Histology of Adrenal Glands

  • Cortex with three zones

    • Secrete steroid hormones called corticoids

    • Outer (glomerular) zone

      • Cells in globular clusters

      • Secretes mineralocorticoids

    • Middle (fascicular) zone

      • Cells form vertical elongated bundles

      • Secrete glucocorticoids

Histology of adrenal glands1
Histology of Adrenal Glands

  • Inner (reticular) zone

    • Cells form irregular, net-like pattern

    • Secrete some sex steroids in both sexes

    • More important in females

      • Affects female sex drive

      • Produces some estrogens

    • Secretion stimulated by ACTH


  • Mineralocorticoids: glomerular zone

    • Aldosterone most important

    • Regulates blood sodium, potassium and acid

    • Regulation affects fluid & electrolyte homeostasis


  • Glucocorticoids from fascicular zone

  • Principle one is cortisol

  • Actions include

    • Response to stress by

      • Glucose formation from fats and protein

      • Conversion of excess glucose to glycogen for storage in liver

      • use of fat for energy assures glucose availability for brain


  • Glucocorticoid actions

    • Reduce inflammation

    • Various steroids including cortisol, cortisone, and synthetic steroids used medically to reduce inflammation

  • Control is by negative feedback

  • Imbalances of glucocorticoids
    Imbalances of Glucocorticoids

    • Addison’s disease

      • Insufficient glucocorticoids

      • Lack of energy

      • Weight loss

      • Inability to resist stress

      • John F. Kennedy had it

    Imbalances of glucocorticoids1
    Imbalances of Glucocorticoids

    • Cushing’s Disease

      • Excessive glucocorticoids

      • Muscle wasting

      • Fat redistribution

      • Spindly arms & legs

      • Large abdomen with stretch marks

      • Rounded face

      • Fatty hump between shoulders

    Addison s disease president kennedy
    Addison’s Disease – President Kennedy

    Before SteroidTreatment

    During SteroidTreatment

    Cushing s syndrome
    Cushing’s Syndrome



    Adrenal medulla
    Adrenal Medulla

    • Develop from same tissue as the sympathetic

      nervous system

    • Chromaffin cells receive direct innervation from sympathetic nervous system

    • Sympathetic stimulation increases hormone secretion by adrenal medulla

    • Hormones are sympathomimetic

      • effects mimic those of sympathetic NS

      • cause fight-flight behavior

    Hormones of adrenal medulla
    Hormones of Adrenal Medulla

    • Catecholamines

    • epinephrine and norepinephrine

    • (adrenaline & noradrenaline)

      • Targets – most cells

      • React quickly to stress by:

        • heart rate and strength

        • blood flow to skeletal muscles, heart and brain

        • Dilation of airways

        • fuel for energy

        • blood pressure


    • Large leaf-shaped gland

    • Located in the curve of small intestine and extend to the spleen

    • Both endocrine and exocrine

      • Endocrine part secretes hormones

      • Exocrine part secretes digestive enzymes

    Anatomy of pancreas
    Anatomy of Pancreas

    • Five inches long, consists of head, body & tail

    • Most cells produce digestive enzymes

    • Endocrine cells in pancreatic islets produce hormones

    Cell organization in pancreas
    Cell Organization in Pancreas

    • Exocrine acinar cells surround a small duct

    • Endocrine cells secrete near a capillary

    Histology of the pancreas
    Histology of the Pancreas

    • 1 to 2 million pancreatic islets

    • Contains 4 types of endocrine cells

    Cell types in the pancreatic islets
    Cell Types in the Pancreatic Islets

    • Alpha cells (20%) produce glucagon

    • Beta cells (70%) produce insulin

    • Delta cells (5%) produce somatostatin

    • PP cells (5%) produce pancreatic polypeptide

    Actions of insulin
    Actions of Insulin

    • Insulin decreases blood glucose by:

      •  uptake of glucose into cells

      • synthesis of liver glycogen for storage

    • Insulin also protein & fat synthesis

    Actions of glucagon
    Actions of Glucagon

    • Glucagon increases blood glucose by:

      • Synthesis of glucose from amino acids in the liver

      • breakdown of liver glycogen into glucose

      • release of glucose from liver into blood

    Regulation of glucagon insulin secretion
    Regulation of Glucagon & Insulin Secretion

    • High blood glucose after a meal stimulates secretion of insulin and inhibits secretion of glucagon

    • Low blood glucose when fasting stimulates release of glucagon and inhibits secretion of insulin

    Diabetes mellitus
    Diabetes Mellitus

    • Insulin is unavailable for uptake of glucose into the cells

    • Or the cells are not responding to insulin

    • Blood glucose levels becomes elevated – hyperglycemia

    Diabetes mellitus1
    Diabetes Mellitus

    • Two Types:

      • Type I (IDDM) or juvenile DM

        • Beta cells destroyed by own immune system

        • Insulin levels low or absent.

        • Insulin injections required.

        • Usually develops in people younger than 20

    Diabetes mellitus2
    Diabetes Mellitus

    • Type II (NIDDM) or maturity onset DM

      • Most common type (90%)

      • Insulin may still be secreted but cells may be less sensitive to its actions

      • Insulin injections may not be required

      • Mostly in people over 35 who are obese

      • May be controlled by diet

    Three signs p s of dm
    Three Signs (P’s) of DM

    • Polyuria

      - Excessive urination

    • Polydypsia

      - Excessive water drinking

    • Polyphagia

      - Excessive eating

    Complications of dm
    Complications of DM

    • Cardivascular disease

    • Loss of vision

    • Kidney disease

      - Most complications linked to high

      glucose and acidosis

      - Acidosis caused by excessive use of

      fat for energy instead of glucose