Anatomy & Physiology

Anatomy & Physiology Digestive System How 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 Animals Epithelial 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 Imaging PET– positron emission tomography - radioactive glucose is injected that cells metabolize; the rate of metabolism is measured to observe areas of unusually high activity. MRI – magnetic resonance imaging - no radiation; 2D images taken in sections to create 3D; show exceptionally clear differences in tissues

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.

Homeostasis Negative 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 food Gizzard – grinds food much like the stomach, but may come before, after, or instead of, a stomach.

Obtaining & Processing Food Mechanical digestion breaks food into physically smaller pieces. Chemical digestion breaks food into smaller molecules by hydrolysis, with the use of enzymes carbs: polysaccharides  monosaccharides fats  saturated/unsaturated fatty acids proteins  amino acids nucleic 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.

Stomach When stimulated by the hormone gastrin, cells of the gastric glands produce gastric juice: a. mucus – made by mucous cells – protects stomach b. hydrochloric acid – by parietal cells – kills bacteria; inactivates salivary amylase; activates pepsinogen c. pepsinogen – by chief cells – turns into the enzyme pepsin at low pH, which begins breaking down proteins into smaller polypeptides

Stomach Heartburn 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 Intestine Chemical 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 Intestine Carbs: • amylase – starch  maltose; then • maltase – maltose  glucose. • lactase – lactose  glucose & galactose. Lipids: lipase  fatty acids. Nucleic acids: nuclease  nucleotides

Small Intestine Proteins: • Trypsin & chymotrypsin create smaller polypeptides • 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.

Nutrition Your 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.

Nutrition Not 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.

Nutrition Important minerals (inorganic substances) • calcium & phosphorus – bone strength • calcium & sodium – nerve & muscle function • sodium, potassium, chlorine – nerves; water balance • iodine – thyroid hormone (metabolism) • iron - hemoglobin

Anatomy & Physiology