Anatomy & Physiology

Digestive SystemHow are the structures of the digestive

system involved in maintaining homeostasis?

Anatomy & Physiology

Anatomy – structure

Physiology – function

The structure always tells you something about the function!

Hierarchy in Animals

cells tissues organs organ systems

4 tissue types in animals:epithelial, connective, muscle, nervous

Hierarchy in AnimalsEpithelial tissue – occurs in tightly packed sheets that line internal & external surfaces. Different tissues are important for protection, absorption of nutrients, or secreting hormones.ex) lining of esophagus; lining of skin; lining of intestine; whole pancreas

Named for:-number of layers of cells (simple:

1 layer; stratified: multiple layers)-shape of cells (squamous = flat;

cuboidal; columnar)

Hierarchy in Animals

Epithelial tissue always has one exposed surface that might face the inside of an organ, or the external environment; the opposite surface (basement membrane) is anchored to fibers & polysaccharides for support.

Hierarchy in Animals

Connective tissue is made of relatively few cells, but lots of “extracellular matrix”, like plasma in blood, or calcium salts in bone. -They perform a variety of functions, mostly in supporting body structures. ex) fascia, fat, blood, cartilage, bone, tendons

Hierarchy in Animals

Muscle tissues enable the body to move.Skeletal – voluntary. lots of striations due to contractile proteins. ex) quadriceps.Smooth – involuntary. lack of striations. ex) intestine.Cardiac – cells are branched in order to relay signals from one cell to the next. heart.

Hierarchy in Animals

Nervous tissue rapidly transmits info from one part of body to another, using cells called neurons

Hierarchy in Animals

Most organs are made of all four tissue types working together.

There are 11 human organ systems: digestive, circulatory, respiratory, excretory, nervous, muscular, skeletal, endocrine, lymphatic, integumentary, reproductive (See matching worksheet.)

Medical Imaging

X-Ray – lots of radiation; 2D images of dense tissues

CT scan – computerized tomography - more radiation; basically an X-Ray taken in sections, so it can be used to create 3D images. Often used with contrast dye to show differences between softer tissues.

Medical ImagingMRI – magnetic resonance imaging - no radiation; 2D images taken in sections to create 3D; show exceptionally clear differences in tissues

PET – positron emission tomography - radioactive glucose is injected that cells metabolize; the rate of metabolism is measured to observe areas of unusually high activity.

Homeostasis

Each of the 11 body systems has special structures that function to maintain homeostasis – a steady internal environment – despite wide fluctuations in the external environment.

HomeostasisNegative feedback is the process the body uses to oppose a stimulus, which returns the internal conditions to normal.

ex) blood sugar; body temperature

Homeostasis

When body temperature rises, blood vessels dilate to bring heat to the surface of the body, and cells produce sweat, which causes cooling as it evaporates.

When body temperature drops, blood vessels to constrict to conserve heat, and muscles constrict which causes shivering.

Obtaining & Processing Food

Most animals are bulk feeders, ingesting large particles of food.

Others are suspension, substrate, or fluid feeders.

Obtaining & Processing Food

Some animals have only a gastrovascular cavity, where food enters & exits through one opening.

Most have an alimentary canal, where food enters then exits through a different opening, allowing for digestion & absorption in specialized compartments.

Obtaining & Processing Food

Different alimentary canals may be made up of a crop, gizzard, and/or stomach.

Crop – softens & stores foodGizzard – grinds food much like the stomach, but may come before, after, or instead of, a stomach.

Obtaining & Processing FoodMechanical digestion breaks food into physically smaller pieces.

Chemical digestion breaks food into smaller molecules by hydrolysis, with the use of enzymes

carbs: polysaccharides monosaccharidesfats saturated/unsaturated fatty acidsproteins amino acidsnucleic acids nucleotides

Human Digestive System

Alimentary canal organs: oral cavity (mouth, tongue), pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus

Digestive glands: salivary glands, pancreas, liver

Oral Cavity

Mechanical digestion by chewing, lubrication with glycoproteins.

Chemical digestion by buffers that neutralize acid, and salivary amylase, which starts hydrolyzing starch.

(Also saliva breaks down bacteria.)

Pharynx & Esophagus

When swallowing, food enters the pharynx (esophagus & trachea opening), then slides over the epiglottis (covers the trachea), and enters the esophagus

The bolus is pushed down the esophagus by peristalsis, NOT GRAVITY.

StomachWhen stimulated by the hormone gastrin, cells of the gastric glands produce gastric juice:

a. mucus – made by mucous cells – protects stomachb. hydrochloric acid – by parietal cells – kills bacteria; inactivates salivary amylase; activates pepsinogenc. pepsinogen – by chief cells – turns into the enzyme pepsin at low pH, which begins breaking down proteins into smaller polypeptides

StomachHeartburn happens when the valve between the esophagus & stomach doesn’t stay closed, and there’s a backflow of gastric juice.

The lining of the stomach must be replaced every three days!

Ulcers happen mostly due to infection with H. pylori, which causes acid & pepsin to damage cells faster than they can regenerate.

Small IntestineChemical digestion occurs in the first 25cm of the small intestine, known as the duodenum.-food leaves the stomach via the pyloric sphincter valve-chyme mixes with bile (made by the liver; stored in gallbladder), which prepares fats for digestion by enzymes-the duodenum & pancreas release compounds to neutralize acid, and SO MANY ENZYMES.

Small IntestineCarbs: a. amylase – starch maltose;

thenb. maltase – maltose glucose. c. lactase – lactose glucose &

galactose.

Lipids: lipase fatty acids.

Nucleic acids: nuclease nucleotides

Small Intestine

Proteins:a. Trypsin &

chymotrypsin create smaller polypeptides

b. Aminopeptidase, carboxypeptidase, and dipeptidase make progressively smaller polypeptides.

Small Intestine

Absorption of nutrients occurs in the remaining ~6m of small intestine;

Villi are fingerlike projections that are lined in microvilli, which together increase the amount of surface area available for absorption.

Small Intestine

Nutrients are absorbed into capillaries & lymph vessels.

The capillaries converge at the hepatic portal vein of the liver, so that nutrients are immediately converted into other substances.

Liver & Pancreas

Large Intestine

Food flows into the large intestine via another valve.The large intestine, or colon, absorbs 90% of water leaving only undigestible plant fiber, and bacteria.Bacteria like E. coli produce several B vitamins (like biotin & folic acid) and Vitamin K.

NutritionYour diet should be high in nutrients but low in Calories!

Essential nutrients must be obtained from diet because they can’t be made from raw materials, but are needed for normal cell functioning.ex) essential fatty acids, essential amino acids

8 out of 20 amino acids are essential and are easily obtained from meat; vegetarians must be sure to eat a variety of plants.

NutritionNot low carb… good carb!

Whole grains are high in fiber without overloading your cells with sugar.

Not low fat… good fat! Saturated fats raise LDL

(bad cholesterol) Trans fats raise LDL & lower

HDL (good cholesterol) Unsaturated fats raise HDL

& lower LDL

Nutrition

Vitamins are coenzymes – necessary for enzyme function

Fat soluble vitamins (A, D, E, K) get stored in your fat if not used, so they can be toxic.

Water soluble vitamins (all the B’s, & C) get peed out if not used. Nontoxic. Mostly.

NutritionImportant minerals (inorganic substances)a. calcium & phosphorus –

bone strengthb. calcium & sodium – nerve &

muscle functionc. sodium, potassium, chlorine

– nerves; water balanced. iodine – thyroid hormone

(metabolism)e. iron - hemoglobin