phys lab quiz

Digestive System consists of

Alimentary Canal
Glands

Alimentary Canal

Tube that runs from mouth to anus. Technically outside of body

Glands of the digestive system

Aid digestion through secretions

Includes: salivary glands (parotid gland, sublingual gland, submadibular gland) liver, pancreas, gastric glands, pyloric glands

Oral cavity

Use teeth, tongue, and salivary gland secretions to masticate food and prepare it for swallowing

Path of the digestive system

Oral cavity --\> pharynx --\> esophagus --\> stomach --\> small intestine --\> large intestine --\> anus

Enzymes do what

change rxn rate and lower activation energy

Enzyme activity is generally highest at

body temperature

Enzyme activity depends on

temperature, pH, substrate concentration, and the presence of any inhibitors or activators.

Pepsin has highest enzyme activity at what pH

2 (pH of stomach)

Salivary amylase has highest enzyme activity at what pH

7 (pH of oral cavity)

Trypsin has highest enzyme activity at what pH

9 (pH of small intestine)

Explain enzyme saturation

As substrate concentration rises, reaction rate rises, but once substrate concentration is high enough the enzyme will become saturated and the reaction rate will stop increasing

What increases surface area in the stomach

rugae - ridges of muscle tissue lining the stomach

What increases surface area of the small intestine

plicae circularis, villi, microvilli

plicae circulares

Transverse ruffles that ring the inner wall of the small intestine.

villi

Fingerlike extensions of the intestinal mucosa that increase the surface area for absorption

microvilli

Tiny projections from the surface of each villus, that help to increase the surface area of the villus.

Enzymes are often embedded in

The wall of the microvilli

Small intestine morphology

Peristalsis

series of peristaltic waves, which involves contraction of circular muscles. These push food along the length of the alimentary canal, against gravity if necessary

Amylase

Secreted from pancreas and salivary glands.
Substrate: starch.
Optimum pH: 6.7 - 7
Products: maltose & short chain glucose molecules

Pepsinogen

Secreted from chief cells
Substrate: protein
Optimum pH: 1.6-2.4
Products: shorter polypeptides

Lipase

Secreted from pancreas
Substrate: triglycerides
Optimum pH: 8.0
Products: fatty acids; monoglycerides

Gastric wall structure

Submucosa
Mucosa - basically stomach lining

The mucosa consists of projections that have chief cells (deepest), parietal cells, and mucous cells (surface).

Between projections - gastric pits

Gastric gland \= each pit lined w these enzymes

Chief cells

secrete pepsinogen

Parietal cells

secrete hydrochloric acid, which makes pH ~2

Mucous cells

secrete mucus, which protects the stomach lining

Reactions in the stomach

Pepsinogen \--- HCl \----\> pepsin

Ingested proteins \----pepsin\-----\> short peptides

Secretions into the small intestine come from

liver and pancreas

Pancreas secretes bile salts, which are responsible for

emulsifying fats

Function of the capillary network of the intestinal villi

To absorb digested products like simple sugars, amino acids, and fatty acids

Lacteal

lymph tubule located in the villus that absorbs fatty acids. lacteals merge to form larger lymphatic vessels that transport the chyle to the thoracic duct where it is emptied into the bloodstream at the subclavian vein

Steps of fat digestion / absorption into brush border cells

Step 1 - emulsification of fat droplets by bile salts
Step 2 - hydrolysis of triglycerides in emulsified fat droplets
Step 3 - Dissolving of fatty acids and monoglycerides into micelles to produce mixed micelles

After *fatty acids* and *monoglycerides* enter brush border cells, what happens to then

apoproteins convert then into chylomicrons

Where do chylomicrons end up

in lacentral lacteal, carried to thoracic duct --\> circulation

How do chylomicrons exit brush border cells

exocytosis

What is the general job of the digestive system

reduce th efoods we eat into small molecules the cells can use to produce ATP

How is the degradation process catalyzed

hydrolytic enzymes

The result of digestion

reduction of carbohydrates to monosaccharides
reduction of proteins to amino acids
reduction of fats to fatty acids and glycerol

Why does the digestive tract has compartments of different pH

Specific enzymes are concentrated in the areas @ pH where they function most effectively

What does movement throughout the digestive tract require

coordinated muscle contractions - peristalsis, segmentation

Difference between peristalsis and segmentation

Segmentation involves contractions of the circular muscles in the digestive tract, while peristalsis involves rhythmic contractions of the longitudinal muscles in the GI tract.

Secretion of enzymes at the proper time is controlled by

neural reflexes and hormones such as gastrin, secretin, cholecystokinin, and gastric inhibitory peptide

Gastrin

A hormone released by the G cells of the stomach in the presence of food. Gastrin promotes muscular activity of the stomach as well as secretion of hydrochloric acid, pepsinogen, and mucus.

Secretin

A hormone secreted by the small intestine (duodenum) in response to low pH (e.g., from stomach acid). It promotes the release of bicarbonate from the pancreas to act as a buffer.

Cholecystokinin

Hormone which causes an increased output of enzyme-rich pancreatic juice and stimulates gallbladder contraction to release bile. Also inhibits gastric motility and secretion.

Gastric inhibitory peptide

Inhibits gastric motility and secretion of acid and stimulates the release of insulin

Where does digestion of carbohydrates begin

in the mouth. salivary glands (parotid, sublingual, and submandibular) secrete amylast called ptyalin that begins the hydrolysis of complex polysaccharides

Benedict's test

measures maltose formation

Lugol's solution

tests for starch

Lugol's solution color in presence of starch

dark purple

Lugol's solution color with no starch present

reddish brown

Benedict's solution when starch converted to maltose

Red

Benedict's solution when maltose has not been formed

blue

Protein digestion begins where

in the stomach

What enzyme is responsible for splitting proteins into shorter polypeptide chains containing amino acids

Pepsin

Which cells secrete pepsinogen

Chief cells in gastric pits

How is pepsinogen activated into pepsin

HCl

Functions of hydrochloric acid

1 - activates pepsin
2 - produces pH of 2, which is optimal for pepsin activity

Peptic ulcer diease

inflammation of the gastric / duodenal mucosa

often caused by helicobacter pylori infection or overuse of NSAIDs such as aspirin and ibuprofen

symptoms: epigastric pain, nausea, pernicious anemia, and life-threatening hemmorhage.

Why is lipase not sufficient to digest fat by itself

It is a water soluble enzyme trying to act on large lipid droplets which are water insoluble

Bile salts

amphipathic molecules with act as emulsifying agents, braking fat into smaller droplets so lipase has a larger surface area for the hydrolysis of fats.

Mixture of bile salts with fat and water \----\>

stable emulsion of small fat droplets in water

Pancreatic colipase

displaces bile salts covering fat dropets, allowing lipase activity within the bile salt coating

How do you quantify digestive activity of lipase

production of aci, indicated by a change in pH

What acid is produced when lipase digests dairy fat

butyric acid

What compound secreted by the pancreas is important in maintaining the pH of ~8-9 in small intestine

sodium bicarbonate

What color is litmus w/ cream

blue

What color is litmus when acid produced

pink

In response to the hormone cholecystokinin, the pancreas secretes

a fluid rich in enzymes.

Functions of the digestive system include which of the following?
A ingestion of foods and liquids
B mechanical processing of food materials and liquids
C boosting expiratory efficiency by lifting the diaphragm via intestinal gas secretions
D warming the body with heat released from the digestive organs as they process food

both A and B

A tube containing starch and saliva, incubated at 37 Celcius will exhibit what color when Lugol's solution is added?

reddish brown, because the amylase will break down the starch

A tube containing starch and water, incubated at 37 Celcius will exhibit what color when Benedict's solution is added?

Blue, because there is no amylase to convert starch to maltose

Bile salts are most important is which type of digestion?

fat

The secretion of this protein by the stomach is the only essential, life sustaining function

intrinsic factor

A tube containing starch and water, incubated at 37 Celcius will exhibit what color when Lugol's solution is added?

purple, because amylase not present

The stomach functions to

Primarily break down foods by mechanical means

Human reproductive cycle

Adult male produces sperm (n) by meiosis + adult female produces ovum (n) by meiosis --\> zygote (2n) \-----\> growth by mitosis \------\> adult male & female

Indifferent gonads

The undifferentiated gonads of the early mammalian fetus, which will eventually develop into either testes or ovaries *depending on whether or not they are stimulated by TDF*

TDF

testes determining factor.
results from presence of SRY gene on Y chromosome.

Effect of TDF on zygote

produces testes, leading to development of seminiferous tubules and interstitial cells in early embryo

Effect of no TDF on zygote

ovaries produced; follicles do not develop until third trimester

What two things influence development of embryonic structures

Testosterone
Müllerian inhibition factor

Where is Müllerian inhibition factor secreted from

AMH is secreted by Sertoli cells of the testes during embryogenesis of the fetal male. In females, it is secreted by the granulosa cells of ovarian follicles.

Paramesonephric duct

In males, degenerates due to Müllerian inhibition factor

In females, gives rise to uterus and uterine tubes

Mesonephric duct

In males, testosterone causes this to develop into epididymides, dactus deferentia, ejaculatory ducts.

In females, degenerates due to lack of testosterone

Other embryonic structures that are effected by presence or absence of testosterone / MIF

males \----- testosterone \-----\> prostate, penis, scrotum


females \------\> vagina, labia, clitoris

Important parts of undifferentiated gonads

Phallus
Glans
Urethral fold
Labioscrotal swelling

Phallus

Forms the external genitalia in both males and females.. basically turns into glans

Glans

the conical mass of erectile tissue that forms the head of the penis / the clitoris

Urethral fold

Forms scrotal raphe in males, labia minora in females.

Labioscrotal swelling

Forms body of penis + scrotum in males, labia major in females.

At what age can you differentiate male from female embryo

12-13 weeks

Outline hormone pathway in males

Hypothalamus stimulated by internal/external factors to release gonadotropin releasing hormone. this stimulates the anterior pituitary to release follicle-stimulating hormone and luteinizing hormone. FSH stimulates secretion of inhibin from seminiferous tubules (specifically from sertoli cells) which inhibits the anterior pituitary from secreting more FSH. LH stimulates secretion of testosterone from the Leydig (interstitial) cells which inhibits anterior pituitary and hypothalamus

Outline hormone pathway in females

Hypothalamus stimulated by internal/external factors to release gonadotropin releasing hormone. This stimulates the anterior pituitary to release follicle-stimulating hormone and luteinizing hormone. These cause increased production of estradiol by ovaries and increased sensitivity of follicles to FSH. This further increases estradiol by positive feedback --\> LH surge which causes ovulation. The empty follicle becomes corpus luteum which secretes estradiol and progesterone. These act on hypothalamus to inhibit GnRH, which inhibits FSH and LH. Decreased estrogen and progesterone causes corpus luteum to regress. The decreased estrogen and progesterone lead to menstruation. Cycle begins again.

Primary sex organ of males

testes

Pathway of sperm through body

Seminiferous tubules
Epididymis
Vas deferens
Ejaculatory duct
N

U - urethra
P - penis

Seminiferous tubules

Narrow, coiled tubules that produce sperm in the testes.

Epidiymis

location of sperm maturation and storage prior to ejaculation

ductus deferens

carries sperm from the epididymis and merges with seminal vesicles to become ejaculatory duct