nutrition
the starting point and the basis
for all human form and function, source of fuel that provides the energy for biological work and the source of raw material for replacement of worn-out biomolecules and cells
metabolism
the chemical changes that lie
at the foundation of form and function; the summation of all catabolic and anabolic processes
weight
determined by the body's energy balance. If energy intake and output are equal, body weight will be stable.
obesity
weight more than 20% above recommended norm for one's
age, sex, and height
BMI
body mass index
-shortens life expectancy
-causes are diverse and unknown
one calorie
heat energy needed to raise the temperature of 1 g of H2O, one degree Celsius
Where does glycolysis occur?
cytoplasm
Where does the Krebs cycle occur?
mitochondria
Where does the electron transport chain occur?
mitochondria
carbohydrates and proteins yield...?
4 kcal/g
fat yields about...?
9 kcal/g
cellular respiration equation
C6H12O6 + 6O2 --> 6CO2 + 6H2O + ATP
anaerobic fermentation
in absence of oxygen the cell
resorts to this one step reaction
what happens in anaerobic fermentation
NADH donates a pair of electrons to pyruvate reducing it to lactic acid
Net result of glycolysis
2 ATP and 2 NADH
Net result of citric acid cycle
6 NADH
2 ATP
2 FADH2
Where do NADH and FADH2 deposit their electrons
into the ETC in the inner mitochondrial membrane
theoretical yield of aerobic respiration
36 ATP
lipolysis
breaking down fat for fuel
How does lipolysis begin?
begins with the hydrolysis of a triglyceride to glycerol and fatty acids
What is lipolysis stimulated by?
epinephrine, norepinephrine, glucocorticoids, thyroid hormone, and growth hormone
What is beta oxidation and where does it occur?
Breakdown of Fatty Acids into two carbon units
- The Mitochondria
the three conversions of amino acids to glucose and fat or directly used as fuel
-deamination
-aminaton
-transamination
Deamination
removal of an amino group (-NH2)
amination
addition of amino group (-NH2)
transamination
transfer of an amino group (-NH2) from one molecule to another
what remains after deamination?
keto acid, which may be converted to pyruvic acid, acetyl-CoA. or on of the acids of the citric acid cycle
four principal mechanisms of communication between cells
1. gap junctions
2. neurotransmiters
3. paracrine (local) hormones
4. hormones
gap junctions
pores in cell membrane allow signaling molecules, nutrients, and electrolytes to move from cell to cell
Neurotransmitters
released from neurons to travel across synaptic cleft to second cell
paracrine hormones
secreted into tissue fluids to affect nearby cells
hormones
chemical messengers that travel in the bloodstream to other tissues and organs
exocrine glands
Have ducts; carry secretion to an epithelial surface or the mucosa of the digestive tract: "external secretions"
Extracellular effects (food digestion)
endocrine glands
-no ducts
-contain dense, fenestrated capilarry networks which allows easy uptake of hormones into blood stream
-internal secretions
intracellular effects such as altering target cell metabolism
two structures composed of pituitary gland (hypohysis)
-andenohypophysis
-neurohypophysis
adenohypophysis
arises from hypophyseal pouch
->anterior pituitary
neurohypophysis
downgrowth from brain
-> posterior pituitary
how many hormones are produces in the hypothalmus? how many regulate the anterior pituitary?
-8 hormones
-6 hormones regulate the anterior
Two other hypothalamic hormones
oxytocin (OT) and antidiuretic hormone (ADH)
Were are OT and ADH stored and released
posterior pituitary
what part produces oxytocin
the left and right paraventricular nuclei
what part produces the antidiuretic hormone?
the supra-optic nuclei
pineal gland
attached to roof of third thalamus ventricle beneath the posterior end of corpus callosum
What does the pineal gland secrete?
sythesizes melatonin from serotonin during the night
thymus
plays a role in three immune systems
-endocrine
-lymphatic
-immune
thymus is the site of....
maturation of t-cells
the thymus secretes what hormones
thymopoietin, thymosin, thymulin
thyroid follicles
sacs that compose most of thyroid
follicular cells
simple cuboidal epithelium that lines follicles
hormones secreted by thyroid and what do they do
thyroxine and triiodothyronine
--->increases metabolic rate
Thyroxine
T4; more abundant
Triiodothyronine
T3; more active
What do parafollicular cells secrete?
calcitonin
What does calcitonin do?
decreases blood calcium levels
PTH (parathyroid hormone)
increases blood calcium and increases absorption of calcium
adrenal medulla
inner core, 10% to 20% of gland
What does the adrenal medulla secrete?
catecholamines (epinephrine and norepinephrine) and a trace of dopamine
adrenal cortex
surrounds adrenal medulla and produces more than 25 steroid hormones called corticosteroids and corticoids
three layers of glandular tissue
-zona glomerulosa
-zona fasciculata
-zona reticularis
zona glomerulosa
secretes aldosterone
zona fasciculata
secretes glucocorticoids (cortisol)
zona reticularis
secretes sex steroids
-androgens and estrogen
Pancreas
exdocrine digestive gland and endocrine cell clusters found retro-peritoneal, inferior and posterior to stomach
Islets of Langerhans
produce hormones
What do beta cells secrete?
insulin
When is insulin secreted?
during and after meal when glucose and amino acid blood levels are rising
What does insulin stimulate?
stimulates cells to absorb nutrients and store or metabolize the by lowering blood glucose levels
glucagen
pancreatic hormone secreted by A or alpha cells
--> raised blood glucose levels
Somatostatin
secreted by delta cells
pancreatic polypeptide
secreted by PP cells or F cells; inhibits gallbladder contraction and secretion pancreatic digestive enzymes
gastrin
secreted by G cells; stimulates stomach acid secretion, motility and emptying
goands
organ that produces the ovaries or testies
exocrine products
whole cells- eggs and sperm (cytogenic glands)
endocrine products
gonadal hormones- mostly steroids
ovarian hormones
estradiol, progesterone, inhibin
testicular hormones
Testosterone, weaker androgens, estrogen, and inhibin
after ovulation what happens to the remains of the follicle
becomes the corpus leteum
corpus luteum
secretes progesterone for 12 days following ovulation
functions of estradiol and progesterone
-development of female reproductive system, bone growth and secondary sexual characteristics
-regulate menstrual cycle and sustain pregnancy
-prepare mammary glands for lactation
inhibin
suppresses FSH secretion from anterior pituitary
seminiferous tubules
Narrow, coiled tubules that produce sperm in the testes.
skin
keratinocytes convert a cholesterol-like steroid into cholecaliferol using UV from the sun-makes vitamin D
liver
involved in the production of at least five hormones
what the the liver secrete
angiotensinogen
hepcidin
promotes intestinal absorption of iron
kidneys
plays role in production of three hormones
What does the kidney produce?
85% erythropoietin
what does the kidneys secrete
renin
What does adipose tissue secrete?
Leptin which slows appetite
stomach and small intestine secrete
-CCK
-gastrin
-ghrelin
peptide YY
osseous tissue- Osteocalcin
secreted by osteoblasts
placenta
secretes estrogens, progesterone, and others
receptors are
protein or glycoprotein molecules
On plasma membrane, in the cytoplasm, or in the nucleus. which act like switches turning on metabolic pathways when hormones binds to them
receptor-hormone interactions exhibit
specificity (specific receptor for each hormone) and saturation (saturated when all receptor molecules are occupied by hormone molecules)
hydrophobic hormones
penetrate plasma membrane and enter nucleus
act directly on the genes changing target cell physiology
estrogen, progesterone, thyroid hormone act on nuclear receptors
take several hours to days to show effect due to lag for protein synthesis
hydrophilic hormones
cannot penetrate into target cell
must stimulate physiology indirectly
modualtion of target cell sensitivity
adjusted by changing the number of receptors
up-regulation
# of receptors is increased
-->sensitivity is increased
down regulation
-reduces # of receptors
--->cells less sensitive
--->happens with long term-term exposure to high hormone concentration
synergistic effect
multiple hormones act together for greater effect
permissive effects
one hormone enhances the target organ's response to a second later hormone
Antagonstic effect
one hormone opposes the action of another
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 cleaf half of hormone from the blood
hyposecretion
inadequate hormone release
hypersecretion
excessive hormone production by an endocrine gland
Pheochromocytoma
tumor of adrenal medulla secretes excessive epinephrine and norepinephrine
toxic goiter
autoantibodies mimic effect of TSH on the thyroid causing thyroid hypersecretion
diabetes mellitus
distruption of metabolism due to hypsecretion or inaction of insulin
symptoms of diabetes mellitus
polyuria, polydipsia, polyphagia
polyuria
excessive urination
polydipsia
excessive thirst
polyphagia
excessive hunger
type 1 diabetes mellitus
insulin dependent
type 2 diabetes
insulin resistance
Five stages of digestion
ingestion, digestion, absorption, compaction, defecation
mechanical digestion
Physical breakdown of large pieces of food into smaller pieces
chemical digestion
a series of hydrolysis reactions that breaks dietary macromolecules into their monomers (residues)
two anatomical subdivisions of the digestive system
1. digestive tract
2.accessory organs
GI tract
stomach and intestines
mucosa
mucous membrane that lines the lumen
mucosa consists of
epithelium, lamina propria, muscularis mucosae
Submucosa
thicker layer of loose connective tissue
muscularis externa
consists of usually two layers of muscle near the outer surface
Serosa
composed of a thin layer of areolar tissue topped by simple squamous mesothelium
adventitia
a fibrous connective tissue layer that binds and blends the pharynx, most of the esophagus, and the rectum into the adjacent connective tissue of other organs
mesenteries
connective tissue sheets that loosely suspend the stomach and intestines from the abdominal wall
parietal peritoneum
a serous membrane that lines the wall of the abdominal cavity
lesser omentum
a ventral mesentery that extends from the lesser curvature of the stomach to the liver
greater omentum
hangs from the greater curvature of the stomach
mesocolon
extension of the mesentery that anchors the colon to the posterior abdominal wall
intraperitoneal
when an organ is enclosed by mesentery on both sides
retroperitoneal
when an organ lies against the posterior body wall and is covered by peritoneum on its anterior side only
the mouth is known as....
oral or buccal cavity
functions of the mouth
--Ingestion (food intake)
--Taste and other sensory responses to food
--Chewing and chemical digestion
Swallowing, speech, and respiration
oral fissure
Anterior opening of the mouth between the lips
fauces
posterior opening to the throat
stratified squamous epithelium
lines mouth
tounge
muscular, bulky, but remarkably agile and sensitive oragn
function of the food
manipulates food between teeth while it avoids being bitten
Root of tounge
posterior one-thirds of toungue occupies the oropharynx
body of the tongue
anterior two-thirds of the tongue occupies oral cavity
function of the teeth
masticate food into smaller pieces
How many adult teeth are there?
32, 16 upper and 16 lower
From midline to the rear of each jaw
2 incisors, 1 canine, 2 premolars, 3 molars
alveolus
tooth socket in bone
Gomphosis
formed between tooth and bone
periodontal ligament
modified periosteum whose collagen fibers penetrate into the bone on one side and into the tooth on the other
gingiva
gums that covers the alveolar bone
regions of a tooth
crown, root, neck, gingival sulcus
crown of a tooth
portion above the gum
root
the portion below the gum, embedded in alveolar bone
dentin
hard yellowish tissue that makes up most of the tooth
enamel
covers crown and neck
Cementum
covers root
saliva
moisten mouth
begins starch and fat digestion
salivary amylase
starch digestion
lingual lipase
activated by stomach acid and digests fat after food is swallowed
intrinsic salivary glands
small glands dispersed amid other oral tissues
lingual glands
in the tongue; produce lingual lipase
-intrinsic
labial glands
inside of the lips
-intrinsic
buccal glands
inside the cheek
-intrinsic
Extrinisc Salivary Glands
three pairs connected to oral cavity by ducts
parotoid gland
anterior to the earlobe
-extrinsic
submandibular gland
located halfway along the body of the mandible
-extrinsic
sublingual gland
located on the floor of the mouth
-extrinsic
Pharynx
a muscular funnel that connects oral cavity to esophagus and allows entrance of air from nasal cavity to larynx
phayngeal constrictors
circular muscles that force food downward during swalling
esophagus
a straight muscular tube 25-30 cm long
--extends from pharynx to cardiac orifice of stomach passing through ESOPHAGUS HIATUS in diaphram
lower esophageal sphincter
-food pauses here because of constriction
-prevents stomach contents from regurgitating into the esophagus
-protects esophageal mucosa from erosive stomach acid
swallowing
a complex action involving over 22 muscles in the mouth, pharynx, and esophagus
Swallowing occurs in two phases
buccal phase and pharyngoesophageal phase
buccal phase of swallowing
voluntary
pharyngoesphageal phase
involuntary
peristalsis
waves of muscular contractions that move food through the digestive tract
stomach
a muscular sac in upper left abdominal cavity immediatley inferior to the diaphram
Chyme
soupy or pasty mixture of semi-digested food in the stomach
The stomach is divided into four regions
cardiac region, fundic region, body, pyloric region
pylroic sphincter
regulates the passae of chyme into the duodenum
muscularis externa of stomach
Three layers of smooth muscle
Inner oblique layer allows stomach to churn, mix, move, and physically break down food
gastric pits
depressions in gastric mucosa
mucous cells
secrete mucus (alkaline)
regenerative (stem) cells
-found in the base of the pit and in the neck of the gland
-divide rapidly and produce a continual supply of new cells to replace cells that die
parietal cells
mostly in the upper half of the gland
What to parietal cells secrete?
hydrochloric acid, intrinsic factor, and ghrelin
chief cells
most numerous, secrete gastric lipase and pepsinogen
Functions of Hydrochloric Acid
- Activates enzymes pepsin & lingual lipase
- Breaks up connective tissues & plant cell walls
>This helps to liquify food to form chyme
- Converts ingested ferric ions (Fe+3) to ferrous ions (Fe+2) that can be absorbed & utilized for hemoglobin synthesis
Zymogens
digestive enzymes secreted as inactive proteins
pepsinogen
secreted by chief cells
gastric lipase
produced by chief cells
intrinsic factor
a glycoprotien secreted by parietal cells
--essential for absorption of vitamin b12
vitamin b12 is needed to.....
synthesize hemoglobin
most digestion and nearly all absorption occur after....
the chyme has passed into the small intestine
stomach is protected in three ways
-mucous coat
-tight junctions
-epithelial cell replacement
Gastric activity is divided into three phases
cephalic phase, gastric phase, intestinal phase
cephalic phase
stomach being controlled by brain
gastric phase
stomach controlling itself
intestinal phase
stomach being controlled by small intestine
liver
reddish brown gland located immediatley inferior to the disphragm
-the bodys largest glands
function of the liver
secretes bile
hepatic lobules
tiny cylinders that fill the interior of the liver
centrak vein of the liver
passing down the core
hepatic sinusoids
Blood-filled channels that fill spaces between the plates
hepatic macrophages (Kupffer cells)
phagocytic cells in the sinusoids that remove bacteria and debris from the blood
functions of hepatocytes
- after a meal > absorb from the blood >> glucose, amino acids, iron, vitamins, and other nutrients for metabolism or storage
- removes and degrades > hormones, toxins, bile pigments, drugs
- secretes into the blood > albumin, lipoproteins, clotting facto
hepatic triad
Two blood vessels and a bile ductule
Gallbladder
a pear-shaped organ about the size of an egg located under the liver
Functions of the gallbladder
serves to store and concentrate bile
Bile
yellow-green fluid containing minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids
Bilirubin
principal pigment derived from the decomposition of hemoglobin
bile acids
steroids synthesized from cholesterol
pancreas
spongy retoperitoneal gland posterior to the greated curvature of the stomach
endocrine portion of pancreas
pancreatic islets that secrete insulin and glucagon
exocrine portion of pancreas
99% of pancreas that secretes 1,200 to 1,500 mL of pancreatic juice per day
pancreatic duct
runs lengthwise through middle of the gland
-joins bile duct at the hepatopancreatic ampulla
accessory pancreatic duct
smaller duct that empties directly into duodenum
pancreatic juice
Alkaline mixture of water, enzymes, zymogens, sodium bicarbonate and other electrolytes
pancreatic zymogens
trypsinogen, chymotrypsinogen, procarboxypeptidase
trypsin
autocatalytic-converts trypsinogen into still more trypsin
small intestine
nearly all chemical digestion and nutrient absorption occurs in small intestine
small intestine divided into three regions
duodenum, jejunum, ileum
circular folds of small intestine
large (macroscopic) folds of submucosa
villi of small intestine
Fingerlike structures formed by the mucosa
Give the small intestine more surface area
mircovilli of small intestine
fuzzy border of microvilli apical surface of each abrorptive cell
fat soluble
Vitamins A, D, E, K