Question

1.Summarize the structure and function of both the digestive system and the excretory system. How do each of these two organ systems participate in ensuring that the body has enough energy and nutrient molecules? How does each system participate in osmoregulation? How does system each participate in eliminating waste?

Please include:  Duodenum, Villi, microvilli, pepsin, protease, chime, jejuno-ileum

• 4 steps, ingestion, digestion, absorption, secretion,
• • Kidneys-

    Glomerulus - ball of arterioles; source of filtrate

    Bowman's capsule – where filtrate is initially absorbed into nephron

    proximal tubule—nutrients are absorbed and liver toxins are secreted

    loop of Henle—sets up concentration gradient in renal medulla

    distal tubule—last adjustment of pH and ion balance

    collecting duct—last adjustment to concentration of urine

  • Ureters
  • Urinary bladder
• Urethra

Answer 1

digestion sytem :

Ingestion : food taken into mouth. there is physical breakdown of food by teeth and presence of saliva secreted by salivary gland which moist and lubricate the food. also the saliva consist of enzyme amylase  which can begin to digest dietary starch into maltose. Saliva also contains lysozyme, an enzyme that lyses many bacteria and prevents the overgrowth of oral microbial populations

Digestion : Through esophagus the food pass to stomach. There is muscular contraction called peristalsis which lead to the movement of food. In stomach there is Gastric juice renders food particles soluble, initiates digestion (particularly of proteins), and converts the gastric contents to a semiliquid mass called chyme, thus preparing it for further digestion in the small intestine. Gastric juice is a variable mixture of water, hydrochloric acid, electrolytes (sodium, potassium, calcium, phosphate, sulfate, and bicarbonate), and organic substances (mucus, pepsins, and protein).Pepsin is the principal acid protease of the stomach. This juice is highly acidic because of its hydrochloric acid content, and it is rich in enzymes. This whole lead to soft paste like food called as chyme which is passes to small intestine.

Through pyloric sphicture present in the downward of stomach, the chyme passes to duodenum of small intestine.

DIGESTION AND ABSORPTION

small intestine is divided into the duodenum, jejunum, and ileum.

• In duodenum pancreatic enzymes , releasing enzymes to break down the products from the stomach, and bicarbonate to neutralize the acid from the stomach before reaching the jejunum. Here the liver introduces bile which allows for the breakdown and absorption of fat from food products.Thousands of microvilli form a structure called the brush border that is found on the apical surface of some epithelial cells, such as the small intestines through which the secretion take place

• The jejunum primary function is absorption, where sugars, amino acids, and fatty acids are absorbed.

• The ileum absorbs nutrients that did not get absorbed by the jejunum, with important nutrients being vitamin B12 and bile acids for reuse.

Composition of Pancreatic Juice

Pancreatic juice is alkaline because of its high content of HCO3−. It neutralizes the acidic chyme from the stomach, aided by the bile and small intestinal juices. In the jejunum, chyme is maintained at a neutral pH as required for the optimal functioning of the pancreatic digestive enzymes. A normal pancreas secretes about 1.5–2 L of juice per day.

Pancreatic juice contains the proenzymes trypsinogen, chymotrypsinogen, procarboxypeptidases, and proelastase. All are activated by trypsin in the intestinal lumen. Enteropeptidase located in the brush border of the jejunal mucosa converts trypsinogen to trypsin. A trypsin inhibitor in pancreatic juice protects against indiscriminate autodigestion from intraductal activation of trypsinogen. In addition, some of the cells lining the small intestine produce a fluid known as ‘succus entericus’ made up mostly of water, mucus and sodium bicarbonate.

There are finger like projection called as villi present int the small intestine surface It function is to  increase the surface area where the absorption take place .Microvilli function as the primary surface of nutrient absorption in the gastrointestinal tract. Because of this vital function, the microvillar membrane is packed with enzymes that aid in the breakdown of complex nutrients into simpler compounds that are more easily absorbed. For example, enzymes that digest carbohydrates called glycosidases are present at high concentrations on the surface of enterocyte microvilli. Thus, microvilli not only increase the cellular surface area for absorption, they also increase the number of digestive enzymes that can be present on the cell surface.

Large Intestine

large intestine is from the ileocecal valve to portion above rectum opening.

The various parts of the large intestine include  ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal. It do not have villi and is involved in absorption of water, electrolytes, vitamins.

It serve a number of functions which include

• absorption of vitamins (B and K)
• produce small fatty acids used as energy by GI epithelial cells
• help breakdown indigestible molecules

EXCRETORY SYSTEM

It is a biological system lead to

1. Collection of water and filter body fluids.
2. Remove and concentrate waste products from body fluids and return other substances to body fluids as necessary for homeostasis.
3. Eliminate excretory products from the body.

excretory system mainly compose of  kidneys, ureters, bladder, and urethra.

Kidney:bean shaped organ . nephron is functional unit of kidney. The nephron consists of a cup-shaped capsule containing capillaries and the glomerulus, and a long renal tube. Blood flows into the kidney through the renal artery, which branches into capillaries associated with the glomerulus. Arterial pressure causes water and solutes from the blood to filter into the capsule. Fluid flows through the proximal tubule, which include the loop of Henle, and then into the distal tubule. The distal tubule empties into a collecting duct. Fluids and solutes are returned to the capillaries that surround the nephron tubule.

Glomerulus is capillary network through which Ultrafiltration take place and glomerulus is surrounded by cup shaped capsule is called bowman capsule. through this waste product is filtered out from body fluid and funnel into ureter.Bowman's capsule with three distinct regions proximal convoluted tubule, the loop of Henle and distal convoluted tubule. The first region is called the proximal convoluted tubule. The proximal convoluted tubule is connected to the second region, the loop of Henle. The loop of Henle has a descending limb and an ascending limb. The third region of the nephron tubule is called the distal convoluted tubule.

Proximal convoluted d tubule

Proximal convoluted tubule of the renal tubule restores much of the filtrate to the blood in the peritubular capillaries, by actively pumping small molecules out of the tubule lumen into the interstitial space. (Water then follows the concentration gradient.)

Loop of Henle

The loop of Henle is a remarkable feature of the renal tubule, associated with the remarkable function of the renal medulla in water conservation. Basically, the loop helps to establish a hypertonic saline environment in the medulla, which in turn allows subsequent recovery of water from collecting ducts (and associated concentration of urine within the collecting ducts).

Distal convoluted tubule

This segment of the renal tubule continues the return of useful materials from the filtrate to the blood in the peritubular capillaries, like the proximal convoluted tubule by actively pumping small molecules out of the tubule lumen into the interstitial space.

Bowman’s capsule surrounds the glomerular capillary loops and participates in the filtration of blood from the glomerular capillaries. Bowman’s capsule also has a structural function and creates a urinary space through which filtrate can enter the nephron and pass to the proximal convoluted tubule. Liquid and solutes of the blood must pass through multiple layers to move from the glomerular capillaries into Bowman’s space to ultimately become filtrate within the nephron’s lumen.Epithelial layer of Bowman’s capsule, which is composed of podocytes. The podocytes feature finger-like projections of cytoplasm referred to as “foot processes” or “pedicels.” These foot processes interdigitate with one another and create a further barrier through which filtrate must pass. Structures called “slit diaphragms” bridge nearby foot processes and provide structural support. The podocytes are the primary cells of the epithelium adjacent to the capillaries (the visceral epithelium) and play a role in filtration. The parietal epithelium of Bowman’s capsule is the outer layer and is composed of simple squamous epithelial cells called “parietal cells.” The parietal layer is not directly involved with filtration from the capillaries. Parietal cells play a structural role in maintaining Bowman’s capsule and are also speculated to have the ability to differentiate into podocytes to replace damaged or old podocytes. Also Tubular reabsorption of water and conserved molecules back into the blood while Tubular secretion of ions and other waste products from surrounding capillaries into the distal tubule.

COLLECTING TUBULE

The functions of the collecting tubes are transportation of urine and absorption of water. It is thought that the tissue of the kidney’s medulla, or inner substance, contains a high concentration of sodium. As the collecting tubules travel through the medulla, the concentration of sodium causes water to be extracted through the tubule walls into the medulla. The water diffuses out between the collecting wall cells until the concentration of sodium is equal in the tubes and outside them. Removal of water from the solution in the tubes serves to concentrate the urine content and conserve body water.

Ureter are the duct through which urine is transport from kidney to urinary bladder

URINARY BLADDER

The urinary bladder is a muscular sac in the pelvis, just above and behind the pubic bone. Urine is stored in this

URETHRA: it is tube through which urine from urinary bladder to outside the body.