Transcript Thyroid and Parathyroid Glands

Found at:
 the base of the throat
Consists of:
 two lobes and a connecting
isthmus
Produces two hormones
1. Thyroid hormone
2. Calcitonin
Thyroid Gland
 1. Thyroid hormone
 Major metabolic hormone
 Composed of two active iodine-
containing hormones
 Thyroxine (T4)—secreted by thyroid
follicles
 Triiodothyronine (T3)—conversion of T4
at target tissues
Thyroid Gland
Thyroid Hormone Disorders
Goiters
 Thyroid
gland enlarges
 In U.S., rarely see goiters due
to lack of iodine because we
use “iodized” salt
Goiters
Thyroid Hormone Disorders
Cretinism
 Caused
by hyposecretion of
thyroxine
 Lack of iodine
 Congenital lack of thyroid gland
 Results in stunted physical and
mental growth during childhood
Cretinism
Thyroid Hormone Disorders
Myxedema
 Caused
by hypothyroidism
in adults
 Results in physical and
mental slugishness
Myxedema
Thyroid Hormone Disorders
 Grave’s Disease
 Caused
by hyperthyroidism
 Results in:
 increased metabolism
 heat intolerance
 rapid heartbeat
 weight loss
 exophthalmos
Exophthalmos
Thyroid Gland
 2. Calcitonin
 Decreases blood calcium levels by
causing its deposition on bone
 Antagonistic to parathyroid hormone
 Produced by parafollicular cells
Parathyroid Gland
 Tiny masses (4) on the posterior of the thyroid
Parathyroid Gland
 Secrete parathyroid hormone (PTH)
 Raise calcium levels in the blood


1. Stimulate osteoclasts to remove calcium
from bone
2. Stimulate the kidneys and intestine to
absorb more calcium
Rising
blood
Ca2+
levels
Calcium homeostasis of blood
9–11 mg/100 ml
Thyroid
gland
Rising
blood
Ca2+
levels
Calcium homeostasis of blood
9–11 mg/100 ml
Calcitonin
Thyroid gland
releases
calcitonin
Thyroid
gland
Rising
blood
Ca2+
levels
Calcium homeostasis of blood
9–11 mg/100 ml
Calcitonin
Thyroid gland
releases
calcitonin
Thyroid
gland
Rising
blood
Ca2+
levels
Calcium homeostasis of blood
9–11 mg/100 ml
Calcitonin
stimulates
calcium salt
deposit
in bone
Calcitonin
Thyroid gland
releases
calcitonin
Thyroid
gland
Rising
blood
Ca2+
levels
Calcium homeostasis of blood
9–11 mg/100 ml
Calcitonin
stimulates
calcium salt
deposit
in bone
Calcium homeostasis of blood
9–11 mg/100 ml
Falling
blood
Ca2+
levels
Calcium homeostasis of blood
9–11 mg/100 ml
Thyroid
gland
Parathyroid
glands
Falling
blood
Ca2+
levels
Calcium homeostasis of blood
9–11 mg/100 ml
Falling
blood
Ca2+
levels
Thyroid
gland
Parathyroid
glands
PTH
Parathyroid
glands release
parathyroid
hormone (PTH)
Calcium homeostasis of blood
9–11 mg/100 ml
Falling
blood
Ca2+
levels
Thyroid
gland
Parathyroid
glands
Osteoclasts
degrade bone
matrix and release
Ca2+ into blood
PTH
Parathyroid
glands release
parathyroid
hormone (PTH)
Calcium homeostasis of blood
9–11 mg/100 ml
Thyroid
gland
Parathyroid
glands
Osteoclasts
degrade bone
matrix and release
Ca2+ into blood
PTH
Parathyroid
glands release
parathyroid
hormone (PTH)
Calcium
Homeostasis
Adrenal Glands
 Sit on top of the kidneys
 Two regions
 1. Adrenal cortex—outer glandular region has
three layers
 A. Mineralocorticoids secreting area
 B. Glucocorticoids secreting area
 C. Sex hormones secreting area
 2. Adrenal medulla—inner neural tissue region.
When stimulated, it releases EPINEPHRINE and
NOREPINEPHRINE
Adrenal Cortex
Adrenal Cortex
 Mineralocorticoid layer secretes ALDOSTERONE
 Aldosterone is important for sodium (Na+) and
potassium (K+) balance; works on kidneys
 Glucocorticoid layer secretes CORTISOL and
CORTISONE
 Help resist long-term stressors
 Released in response to increased blood levels of
ACTH
 Sex hormone layer secretes small amount of
ANDROGENS and ESTROGENS
Short term
Stress
Hypothalamus
Short term
Stress
Hypothalamus
Nerve impulses
Spinal cord
Short term
Stress
Hypothalamus
Nerve impulses
Spinal cord
Preganglionic
sympathetic
fibers
Adrenal
medulla
Short term
Stress
Hypothalamus
Nerve impulses
Spinal cord
Preganglionic
sympathetic
fibers
Adrenal
medulla
Catecholamines
(epinephrine and
norepinephrine)
Short-term
stress response
Stress
Hypothalamus
More prolonged
Stress
More prolonged
Hypothalamus
Releasing hormone
Corticotropic cells of
anterior pituitary
ACTH
Adrenal
cortex
More prolonged
Stress
Hypothalamus
Releasing hormone
Corticotropic cells of
anterior pituitary
ACTH
Mineralocorticoids
Adrenal
cortex
Glucocorticoids
Long-term stress response
Adrenal cortex disorders
Addison’s disease
 Results
from hyposecretion of
all adrenal cortex hormones
 Bronze skin tone, muscles are
weak, burnout, susceptibility to
infection
Adrenal cortex disorders
Adrenal cortex disorders
 Cushing’s syndrome
 Results
from a tumor in the middle
cortical area of the adrenal cortex
 Characterized by:
 “Moon face”
 “Buffalo hump” on the upper back
 High blood pressure
 Increased blood sugar
 Depression
Cushing’s Syndrome
Pancreas
 The pancreas is
a mixed gland
and has both
endocrine and
exocrine
functions
Pancreatic Islets: 2 Hormones
 1. Insulin (beta cells): allows glucose to
cross plasma membranes into cells
 2. Glucagon (alpha cells): allows glucose
stored in cells to be released into the blood
Homeostasis: Normal blood glucose
levels (90 mg/100ml)
Stimulus:
rising blood
glucose levels
(e.g., after
eating four
jelly doughnuts)
Homeostasis: Normal blood glucose
levels (90 mg/100ml)
Elevated
blood sugar
levels
Stimulus:
rising blood
glucose levels
(e.g., after
eating four
jelly doughnuts)
Homeostasis: Normal blood glucose
levels (90 mg/100ml)
Insulin-secreting
cells of the pancreas
activated; release
insulin into the
blood
Elevated
blood sugar
levels
Stimulus:
rising blood
glucose levels
(e.g., after
eating four
jelly doughnuts)
Homeostasis: Normal blood glucose
levels (90 mg/100ml)
Insulin-secreting
cells of the pancreas
activated; release
insulin into the
blood
Uptake of glucose
from blood is enhanced in most
body cells
Elevated
blood sugar
levels
Stimulus:
rising blood
glucose levels
(e.g., after
eating four
jelly doughnuts)
Homeostasis: Normal blood glucose
levels (90 mg/100ml)
Insulin-secreting
cells of the pancreas
activated; release
insulin into the
blood
Elevated
blood sugar
levels
Stimulus:
rising blood
glucose levels
(e.g., after
eating four
jelly doughnuts)
Uptake of glucose
from blood is enhanced in most
body cells
Liver takes up
glucose and stores
it as glycogen
Homeostasis: Normal blood glucose
levels (90 mg/100ml)
Insulin-secreting
cells of the pancreas
activated; release
insulin into the
blood
Elevated
blood sugar
levels
Stimulus:
rising blood
glucose levels
(e.g., after
eating four
jelly doughnuts)
Uptake of glucose
from blood is enhanced in most
body cells
Liver takes up
glucose and stores
it as glycogen
Homeostasis: Normal blood glucose
levels (90 mg/100ml)
Blood glucose
levels decline
to set point;
stimulus for
insulin release
diminishes
Homeostasis: Normal blood glucose
levels (90 mg/100ml)
Stimulus:
declining blood
glucose levels
(e.g., after
skipping a meal)
Homeostasis: Normal blood glucose
levels (90 mg/100ml)
Stimulus:
declining blood
glucose levels
(e.g., after
skipping a meal)
Low blood
sugar levels
Homeostasis: Normal blood glucose
levels (90 mg/100ml)
Stimulus:
declining blood
glucose levels
(e.g., after
skipping a meal)
Low blood
sugar levels
Glucagon-releasing
cells of pancreas
activated;
release glucagon
into blood; target
is the liver
Homeostasis: Normal blood glucose
levels (90 mg/100ml)
Stimulus:
declining blood
glucose levels
(e.g., after
skipping a meal)
Low blood
sugar levels
Liver breaks down
glycogen stores and
releases glucose to
the blood
Glucagon-releasing
cells of pancreas
activated;
release glucagon
into blood; target
is the liver
Homeostasis: Normal blood glucose
levels (90 mg/100ml)
Stimulus:
declining blood
glucose levels
(e.g., after
skipping a meal)
Low blood
sugar levels
Rising blood
glucose levels
return blood sugar
to homeostatic set
point; stimulus for
glucagon release
diminishes
Liver breaks down
glycogen stores and
releases glucose to
the blood
Glucagon-releasing
cells of pancreas
activated;
release glucagon
into blood; target
is the liver
Pineal Gland
 Found on the third ventricle of the brain
Pineal Gland
 Called the “third eye” because it receives
visual information from the retina regarding
light and dark
 Secretes melatonin
 Helps establish the body’s wake and
sleep cycles