Human Physiology Flashcards
Digestion
Breakdown of food into smaller pieces for effective absorption by the villi into the bloodstream.
Mouth
Voluntary control of eating and swallowing, mechanical digestion of chewing and chemical starch digestion by saliva, which contains lubricants and enzymes
Esophagus
Movement of food by peristalsis from mouth to the stomach
Stomach
Churning and mixing with secreted water and acid to kill foreign bacteria and other pathogens in food and to initiate protein digestion
Small Intestine
Final stages of digestion, neutralizing stomach acid and absorb nutrients
Pancreas
Lipase, amylase and protease secretion to aid digestion
Liver
Secretion of surfactants in bile to break up lipid droplets
Gallbladder
Storage and regulated release of bile
Large intestine
Re - absorption of water, further digestion especially of carbohydrates, formation and storage of feces
Digestion Full Process
- Food is chewed in the mouth, turned into bolus by amylase
- Bolus enter the esophagus, move to the stomach by peristalsis
- Stomach churns food with acid, becoming chyme. Acid kills bacteria and starts protein digestion
- Chymes enters small intestine, where acid needs to be neutralized. Enzymes in SI have optimum pH for digesting lipids or further digest carbohydrates and proteins. Absorption starts at the beginning of the ileum
- Food enters large intestine: undigested material and digestive juices. Water, vimatins K and B, minerals reabsorbed
- Feces formed in LI stored in the rectum before egestion
Peristalsis
The longitudinal muscle contracts to widen the lumen, allowing the bolus to move down. The circular muscle contracts to constrict the lumen, pushing it further down.
Mechanical Digestion
Physically breaking down food through chewing, grinding, churning into smaller pieces
Chemical Digestion
Breaking down food into its basic components using enymes.
Pancreatic Amylase
Secreted by the pancreas into the small intestine, breaks down starch into maltose. Optimal pH of 7
Pepsin
Secreted by the stomach into the stomach, breaks down proteins into amino acids. Optimal pH of 2
Pancreatic Lipase
Secreted by the pancreas into the small intestine, breaks down triglycerides into glycerol and fatty acids. Optimal pH of 7.2
Lipid Digestion
- Fat globule separated into smaller micelles by bile (amphiphilic)
- The hydrophobic side attaches to the emulsified droplets, exposing the hydrophilic side to the exterior to prevent the droplets from reforming
- The pancreas secretes lipase after to conduct hydrolysis
Protein Digestion
- Pepsin in the stomach breaks protein chains into peptones and proteoses
- In the small intestine, trypsin and chymotrypsin break peptones and proteoses into single or double amino acid units
- Hydrolysis occurs to separated amino acids
Carbohydrate Digestion
- Salivary amylase breaks up long chains
- In the small intestines, pancreatic enzymes break dissacharides into monosaccharides
Acinar Cells
Found in the pancreas, secrete digestive enzymes
Path of Pancreatic Enzymes from Stomach to SI
Pancreatic juice containing the enzymes, carried through the pancreatic duct to the duodenum, released into the lumen of the SI
Examples of SI Enzymes
- Nuclease break down DNA and RNA
- Maltase breaks down maltose into glucose
- Lactase: lactose into galactose and glucose
Absorption
The movement of nutrients from the digestive system into the body through the bloodstream. Mostly occurs in the small intestine
Structure of the Small Intestine
- Folds in the lining increases SA with villi and microvilli
- Layers from inner to outer: mucosa, submucosa, muscularis and serosa
Muscularis Layer of the Small Intestine
Two smooth muscle layers. One thin outer longitudinal layer that shortens and elongates the intestine. Two a thicker inner circular layer causes constriction. Nerves lie between these two layers and allow them to work together to propagate food proximal (closer) to distal (further): peristalsis
Villus
- Present in a large amount to increase SA
- Rich blood supply to aid in absorption of nutrients into the blood, including bases of nucleic acids, vitamins and minerals
- Microvilli present as outward folds of the plasma membrane to increase SA
- Contain lacteals to aid in lipid absorption
- Intestinal crypts, glandular cells that secrete fluids to aid in movement of chyme through the intestine
- Thin epithelium to increase diffusion rate
- Capillaries to absorb glucose and amino acids
Methods of Absorption: Villi
Simple and facilitated diffusion, active transport and pinocytosis
Functions of the 4 Layers of the Small Intestine
- Mucosa: epithelium formed by enterocytes, goblet cells and endocrine cells
- Submucosa: contains blood vessels and connective tissue
- Muscularis: conducts peristalsis
- Serosa: single layer of epithelial cells with connective tissue
Enterocyte
Cells with microvilli, absorb glucose
Goblet Cells
Produce mucus
Lipid Absorption (5 Step Process)
- Fatty acids enter the epithelial cell
- Synthesis of fats in endoplasmic reticulum
- Fats form chylomicrons, a lipoprotien particle that transport fats
- Chylomicrons enter the lacteal
- Lymph transports chylomicrons
Dialysis Tubing
Models absorption
- A partially permeable membrane cellulose tubing containing microscopic pores that allow water, small molecules and ions to pass
- Separation of smaller molecules from large molecules in solution by selective diffusion
- Iodine: black if starch is present, orange if absent
- Benedict’s becomes brick red if glucose is present, blue if absent
2 Functions of the Respiratory System
- Gas exchange for cellular respiration
- Ventilation
Nasal and Oral Cavity
Where air enters the respiratory system
Pharynx
The membrane lined cavity behind the nose and mouth, connecting them to the esophagus or trachea
Larynx
Hollow muscular tube forming a passage to the lungs and holding the vocal cords
Trachea
Tube reinforced by rings of cartilage, extending from the larynx to the bronchi, conveying air to and from the lungs
Lungs
RIght lungs has three lobgs, left two. Conduct inspiration and expiration to bring in oxygen and removed carbon dioxide
Bronchi, bronchioles
Pathways of air into the lungs
Alveoli
Tiny air sacs at the end of bronchioles
Pathway of Air into the Respiratory System
Nasal and oral cavity, pharynx, larynx, trachea, lungs, bronchi, bronchioles, alveoli
Alveolar Cells
Type 1 and II pneumocytes
Type I Pneumocytes
Extremely flat and thin alveolar cells to increase SA for diffusion. Amniotic and unable to replicate but can form from type II pneumocytes.
Type II Pneumocytes
Secretes surfactants that create a moist surface and increases gas exchange, preventing alveoli from sticking to each otherS
Surfactant
Water based solution containing phospholipoproteins
Gas Exchange Summary
Replacing carbon dioxide with oxygen in the blood in lungs
How Gas Exchange Supports Cellular Respiration
Obtains oxygen and removes carbon dioxide for ATP synthesis.
Gas exchange occurs through diffusion, driven by the difference in [O] between x and y, a and b
x: cells
y: blood
a: lungs
b: external environment
Purpose of Branching of Airways in the Respiratory System
Increase surface area to increase efficiency of gas exchange
The longer air remains in the alveolus, the a the [O], b the concentration gradient that drives diffusion of oxygen
a: lower
b: decreasing
Alveolar [O] compared to [O] in blood that flows past the alveoli
Higher
Alveolar [CO2] comapred to [CO2] in blood that flows past the alveoli
Lower
2 Locations of Gas Exchange
- Blood and external environment at the alveoli
- Cells and blood at the capillaries
Ventilation Definition
Muscle movement to move fresh air into alveoli
Ventilation Responsibility
Maintaining a concentration gradient for exchange to occur between air in the alveoli and blood in capillaries