Topic 6: Human Physiology Flashcards
Describe the villi and microvilli function and structure in the small intestine.
Vili increases the surface area of epithelium over which absorption is carried out. It also absorbs monomers formed by digestion as well as mineral ions and vitamins. Intestinal villi contain several key features which faciliate the absorption of digestive products (monomers, ions, and vitamins): MR SLIM
- Microvilli: ruffling of epithelial membrane further increases surface area
- Rich blood supply: dense capillary network rapidly transports absorbed products
- Single layer epithelium: minimises diffusion distance between lumen and blood
- Lacteals: absorb lipids from the intestine into the lymphatic system
- Intestinal glands: exocrine pits (crypts of Lieberkuhn) release digestive juices
- Membrane proteins: faciliatates transport of digested materials into epithelial cells
Microvilli: borders significantly increases surface area of the plasma membrane (>100x), allowing for more absorption to occur. The membrane will be embedded with immobilised digestive enzymes and channel proteins to assist in material uptake.
The small intestine is composed of four main tissue layers, which are (from outside to centre):
- Serosa: a protective outer covering composed of a layer of cells reinforced by fibrous connective tissue
- Muscle layer: outer layer of longitudinal muscle (peristalsis) and inner layer of circulr muscle (segmentation)
- Submucosa: composed of connective tissue separating the muscle layer from the innermost mucosa
- Mucosa: a highly folded inner layer which absorbs material through its surface epithelium from the intestinal lumen
Outline the way in which nutrients are absorbed in the body.
During absorption, digested food monomers must pass from the lumen into the epithelial lining of the small intestine
- tight junctions between epithelial cells occlude any gaps between cells - all monomers must cross the membrane
- different monomers undertake different methods for crossing the apical and basolateral membranes
List the different membrane transport mechanisms and how they work.
Different methods of membrane transport are required to absorb different nutrients
Secondary Active Transport:
- A transport protein couples the active translocation of one molecule to the passive movement of another (co-transport)
- Glucose and amino acids are co-transported across the epithelial membrane by the active translocation of sodium ions (Na+)
- For glucose and amino acids
Facilitated Diffusion
- Channel proteins help hydrophilic food molecules pass through the hydrophobic portion of the plasma membrane
- Channel proteins are often situated near the specific membrane-bound enzymes (creates a localized concentration gradient)
- Certain monosaccharides (e.g. fructose), vitamins, and some minerals are transported by facilitated diffusion
- For monosaccharides
Osmosis
- Water molecules will diffuse across the membrane in response to the movement of ions and hydrophilic monomers (solutes)
- The absorption of water and dissolved ions occurs in both the small and large intestine
- For water
Simple Diffusion
- Hydrophobic materials (e.g. lipids) may freely pass through the hydrophobic portion of the plasma membrane
- Once absorbed, lipids will often pass first into the lacteals rather than being transported via the blood
- For triglycerides
Describe the processes occurring in the small intestine that result in the digestion of starch and digestion to the liver.
Starch is a polysaccharide composed of glucose monomers and accounts for ~60% of the carbohydrates consumed by humans
- Starch can exist in one of two forms - linear chains (amylose) or branched chains (amylopectin)
The digestion of starch is initiated by salivary amylase in the mouth and continued by pancreatic amylase activity (optimal pH ~ 7)
Amylase digests amylose into maltose subunits (disaccharide) and digests amylopectin into branched chains called dextrins
- Both maltose and dextrin and digested by enzymes (maltase) which are fixed to the epithelial lining of the small intestine
- The hydrolysis of maltose/dextrin results in the formation of glucose monomers
Glucose can be hydrolyzed to produce ATP (cell respiration) or stored in animals as the polysaccharide glycogen
- Glucose monomers can be generated from the breakdown of other disaccharides (such as lactose and sucrose)
What is the role of the pancreas?
The pancreas served two functions in the breakdown of starch:
- It produces the enzyme amylase which is released from exocrine glands (acinar cells) into the intestinal tract
- It produces the hormones insulin and glucagon which are released from endocrine glands (islets of Langerhans) into the blood
The hormones insulin and glucagon regulate the concentration of glucose in the bloodstream (controls availability to cells)
- Insulin lowers blood glucose levels by increasing glycogen synthesis and storage in the liver and adipose tissues
- Glucagon increases blood glucose levels by limiting the synthesis and storage of glycogen by the liver and adipose tissues
Identify and label the heart structure, as well as blood vessels.
Outline the differences between arteries, veins, and capillaries.
Arteries convey blood at high pressure from the ventricles to the tissues of the body. They have muscle cells and elastic fibers in their walls. The muscle and elastic fibers assist in maintaining blood pressure between pump cycles.
Capillaries have permeable walls that allow the exchange of material between cells in the tissue and the blood in the capillary.
Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart.
Describe the cardiac cycle.
Outline the role of the pacemaker.
Pacemakers are medical devices that are surgically fitted in patients with malfunctioning sinoatrial nodes. The devices maintain the rhythmic nature of the heartbeat. They can provide a regular impulse or discharge only when a heartbeat is missed so that it beats normally. The most common is the one that monitors heartbeat and initiates one if a beat is missed. The ventricle is stimulated with a low-voltage pulse.
Explain antibiotic resistance in bacteria strains.
Describe Florey and Chain’s experiments, leading to the discovery of penicillin.
Explain the antibody production.
Explain the ventilation mechanism.
Outline the effect of exercise on ventilation.
Identify the role of Type I and II pneumocytes and the difference between them.
How does a nerve impulse pass along the neuron?
Explain the synapse transmission.
How do pesticide neonicotinoids kill insects?
