Human Biology: Small Intestine Functions
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Questions and Answers

What role do the finger-like projections called villi play in the small intestine?

  • They regulate the flow of food through the intestine.
  • They serve as storage for undigested food.
  • They reduce the absorption of water and nutrients.
  • They increase the surface area for absorption of digested food. (correct)

    • What is the main function of the blood capillaries found within each villus?

  • To cleanse toxins from the absorbed nutrients.
  • To digest fats before they are absorbed.
  • To facilitate the absorption of water and mineral salts.
  • To quickly transport absorbed glucose and amino acids. (correct)

    • Why is it important for the epithelium of the villus to be only one cell thick?

  • It allows for a longer diffusion path.
  • It reduces the diffusion distance for nutrient absorption. (correct)
  • It supports the digestion of complex carbohydrates.
  • It prevents the absorption of excess nutrients.

    • How do microvilli contribute to the small intestine's function?

    <p>They further increase the surface area for absorption.</p> Signup and view all the answers

    What is the function of the lacteal located within each villus?

    <p>It transports absorbed fats away from the intestine.</p> Signup and view all the answers

    What happens to water and mineral salts in the small intestine and colon?

    <p>Most water is absorbed in the small intestine before reaching the colon.</p> Signup and view all the answers

    What is the significance of maintaining a diffusion gradient in the context of nutrient absorption?

    <p>It promotes the rapid absorption of digested food.</p> Signup and view all the answers

    Which of the following adaptations is NOT found in the small intestine to aid in absorption?

    <p>Thick multi-layered epithelium.</p> Signup and view all the answers

    What role do the beta cells from the islets of Langerhans play in blood glucose regulation?

    <p>They secrete insulin to increase glucose uptake.</p> Signup and view all the answers

    How does glucagon affect blood glucose levels?

    <p>It stimulates the conversion of glycogen to glucose.</p> Signup and view all the answers

    Which hormone decreases the permeability of cells in the collecting duct to water?

    <p>Anti-diuretic hormone (ADH)</p> Signup and view all the answers

    What physiological response occurs when there is an increase in skin temperature?

    <p>Blood flow to the skin increases to promote heat loss.</p> Signup and view all the answers

    What happens to blood glucose concentration during the secretion of insulin?

    <p>It decreases.</p> Signup and view all the answers

    Which receptors are responsible for detecting changes in blood glucose concentration?

    <p>Islets of Langerhans</p> Signup and view all the answers

    What typically occurs when blood glucose levels decrease below normal?

    <p>Glucagon is secreted to raise glucose levels.</p> Signup and view all the answers

    During the maintenance of homeostasis, what triggers the secretion of anti-diuretic hormone (ADH)?

    <p>Decrease in water potential</p> Signup and view all the answers

    How does an increase in blood glucose concentration affect respiration rates in cells?

    <p>Respiration rates increase.</p> Signup and view all the answers

    What condition is characterized by an inability to regulate blood glucose concentration?

    <p>Diabetes</p> Signup and view all the answers

    What process happens to excess glucose when insulin is secreted?

    <p>It is converted to glycogen.</p> Signup and view all the answers

    What role do osmoreceptors play in homeostasis?

    <p>They monitor blood water potential.</p> Signup and view all the answers

    How does the body respond to a decrease in skin temperature?

    <p>Hair erector muscles contract to trap more heat.</p> Signup and view all the answers

    What physiological changes occur when the concentration of water potential increases in the blood?

    <p>ADH production is decreased.</p> Signup and view all the answers

    What role do mitochondria play in epithelial cells?

    <p>They provide energy for active transport of nutrients.</p> Signup and view all the answers

    What is the primary function of the colon in digestion?

    <p>Absorption of water and mineral salts.</p> Signup and view all the answers

    How is excess glucose stored in the body?

    <p>As glycogen in the liver and muscles.</p> Signup and view all the answers

    What happens to excess amino acids in the liver?

    <p>They are deaminated to form urea.</p> Signup and view all the answers

    What is the role of bile in digestion?

    <p>To emulsify fats into smaller droplets.</p> Signup and view all the answers

    What is a potential consequence of heavy alcohol consumption?

    <p>Increased risk of liver cirrhosis.</p> Signup and view all the answers

    What occurs during egestion?

    <p>Waste is temporarily stored and expelled.</p> Signup and view all the answers

    What is the effect of fermentation in the colon?

    <p>Production of vitamins B and K.</p> Signup and view all the answers

    What major function does the pancreas serve in digestion?

    <p>Production of pancreatic juice containing digestive enzymes.</p> Signup and view all the answers

    How do fats enter the bloodstream after absorption?

    <p>Via the lymphatic capillaries.</p> Signup and view all the answers

    What may happen to a fetus if alcohol is consumed heavily during pregnancy?

    <p>Interference with brain development.</p> Signup and view all the answers

    What observation indicates the presence of starch in a mixture?

    <p>The mixture turns blue.</p> Signup and view all the answers

    What is the immediate effect of alcohol consumption on reaction times?

    <p>Decreased reaction times.</p> Signup and view all the answers

    What role do the hepatic portal vein and hepatic artery serve?

    <p>Transport blood between the liver and intestines.</p> Signup and view all the answers

    What is the primary form of energy used during bulk transport across the cell membrane?

    <p>Energy in the form of ATP</p> Signup and view all the answers

    Which type of transport involves the ingestion of white blood cells?

    <p>Endocytosis</p> Signup and view all the answers

    What is the purpose of ATP in cellular processes?

    <p>To provide energy for cellular functions</p> Signup and view all the answers

    During which process are nutrients such as proteins taken up by microvilli in the human small intestines?

    <p>Pinocytosis</p> Signup and view all the answers

    What characterizes exocytosis in cellular transport?

    <p>It results in the release of substances like enzymes.</p> Signup and view all the answers

    What happens when blood glucose concentration exceeds the kidneys' reabsorption capacity?

    <p>Glucose is excreted in the urine.</p> Signup and view all the answers

    Which hormone is primarily deficient in Type 1 diabetes?

    <p>Insulin</p> Signup and view all the answers

    Which of the following is a common risk factor for Type 2 diabetes?

    <p>High cholesterol levels</p> Signup and view all the answers

    What is the primary function of the cornea in the eye?

    <p>To refract light rays into the eye</p> Signup and view all the answers

    Which part of the eye is involved in focusing light onto the retina?

    <p>Lens</p> Signup and view all the answers

    How does the pupil react in bright light conditions?

    <p>Constricts to reduce light entry</p> Signup and view all the answers

    What is the role of the ciliary muscles in the eye?

    <p>To regulate the curvature of the lens</p> Signup and view all the answers

    What occurs during deamination of excess amino acids in the liver?

    <p>Production of urea</p> Signup and view all the answers

    Which part of the eye contains no rods or cones?

    <p>Blind spot</p> Signup and view all the answers

    What is the primary role of the tear gland?

    <p>To lubricate the cornea</p> Signup and view all the answers

    How does the eye accommodate for near objects?

    <p>Lens becomes thicker</p> Signup and view all the answers

    What substance is primarily responsible for maintaining the shape of the eyeball?

    <p>Vitreous humour</p> Signup and view all the answers

    Which structure in the eye helps control light entry?

    <p>Iris</p> Signup and view all the answers

    What is the main purpose of excretion in the body?

    <p>To remove metabolic waste and toxins</p> Signup and view all the answers

    Study Notes

    Digestion Process

    • Small Intestine: Absorbs most of the water before food moves to the colon. Minute fat globules enter the lacteals.
    • Colon: Absorbs water and mineral salts from undigested food. Ferment vitamins with colonic bacteria (e.g., vitamins B and K).

    Adaptations of the Small Intestine for Absorption

    • Villi: Finger-like projections that increase the surface area for faster absorption of digested food.
    • Blood Capillaries: Allow blood to quickly transport absorbed glucose and amino acids, maintaining a diffusion gradient.
    • Lacteals: Allow rapid transport of absorbed fats, maintaining a steep diffusion gradient.
    • Epithelium (Wall): One-cell thick, providing a short diffusion distance for absorbed food.
    • Microvilli: Increase surface area for absorption.
    • Mitochondria: Provide energy for active transport of nutrients into the villi.

    Assimilation

    • Glucose: Assimilated and broken down during cellular respiration to release energy for cell functions. Excess glucose is stored as glycogen.
    • Protein: Amino acids are used to build new cytoplasm for growth and repair of cells, form enzymes and hormones. Excess amino acids are deaminated in the liver.
    • Fats: Absorbed into lymphatic capillaries, which discharge fat into the bloodstream.
      • Fats are used to build protoplasm if glucose is abundant.
      • Fats are used to provide energy if glucose is scarce.
      • Excess fats are stored in adipose tissue.

    Egestion

    • Rectum: Temporarily stores faeces.
    • Anus: Ejects faeces when the rectum contracts.

    Role of Other Organs in Digestion

    • Pancreas: Produces pancreatic juice containing enzymes (amylase, protease, lipase) that are secreted by the pancreatic duct into the small intestine.
    • Bile Duct: Secretes bile into the small intestine.
      • Bile salts emulsify fats by breaking them into smaller droplets, increasing the surface area for lipase activity.
    • Liver:
      • Hepatic Portal Vein: Transports blood rich in amino acids and glucose from the small intestine to the liver.
      • Hepatic Vein: Distributes remaining amino acids and glucose to body parts.
      • Hepatic Artery: Transports blood rich in oxygen to the liver.
      • Production of Bile: Helps digest fats.
      • Deamination of Amino Acids: Removes amino groups from amino acids and converts them to urea.
      • Detoxification: Removes harmful substances like alcohol and benzoic acid.
      • Glucose Regulation: Regulates blood glucose concentration.

    Effects of Alcohol Consumption on the Brain

    • Temporary Effects:
      • Increased reaction time.
      • Reduced self-control leading to risky behavior like drunk driving.
      • Blurred vision, poor judgment, and poor coordination.
    • Long-Term Effects:
      • Increased risk of gastric ulcers.
      • "Wet Brain" (dementia).
      • Shrinkage of brain volume.
      • Fetal brain development problems during pregnancy.
      • Liver cirrhosis (liver cells destroyed and replaced with fibrous tissue) leading to liver failure.
    • Societal Implications:
      • Neglect of work and family.
      • Violent behavior.
      • Increased criminal activity.

    Starch Test, Benedict’s Test, Biuret Test, Fats test

    • Starch Test: Turns from orange to blue-black if starch is present. Remains orange if absent.
    • Benedict’s Test: Turns from blue to red if reducing sugars are present. Remains blue if absent.
    • Biuret Test: Turns from blue to violet if protein is present. Remains blue if absent.
    • Fats Test: Forms a milky solution if lipid is present.

    Homeostasis & Hormones

    • Definition: Maintaining a constant internal environment.
    • Negative Feedback Process: A mechanism to regulate internal conditions by reversing any changes made to maintain a stable state.

    Blood Glucose Regulation

    • Increase in Blood Glucose: Beta cells in the islets of Langerhans secrete insulin. Insulin increases cell permeability to glucose, stimulating glucose uptake and cell respiration. Excess glucose is converted to glycogen. Blood glucose concentration returns to normal.
    • Decrease in Blood Glucose: Alpha cells in the islets of Langerhans secrete glucagon. Glucagon stimulates the conversion of glycogen to glucose. Blood glucose concentration returns to normal.

    Water Potential Regulation

    • Increase in Water Potential: Osmoreceptors in the hypothalamus detect the change. The hypothalamus signals the pituitary gland to decrease ADH production. Decreased ADH lowers the permeability of the collecting duct to water, decreasing water absorption. Blood potential returns to normal.
    • Decrease in Water Potential: Osmoreceptors in the hypothalamus detect the change. The hypothalamus signals the pituitary gland to increase ADH production. Increased ADH increases the permeability of the collecting duct to water, increasing water absorption. Blood potential returns to normal.

    Skin Temperature Regulation

    • Increase in Skin Temperature: Thermoreceptors in the skin detect the change. Arterioles dilate, increasing blood flow to the skin for heat loss. Sweat glands increase sweat production for evaporative cooling. Skin temperature returns to normal.
    • Decrease in Skin Temperature: Hair erector muscles contract, causing hair to stand on end to trap heat.

    Diabetes

    • Definition: A condition where blood glucose concentration cannot be regulated.

    Diabetes

    • Blood glucose concentration exceeding the kidneys’ reabsorption capacity results in glucose being excreted in urine.
    • Type 1 diabetes is inherited and characterized by the inability of the Islets of Langerhans to produce or secrete sufficient insulin.
      • Management involves regular blood glucose and urine testing, careful diet, and regular insulin injections.
    • Type 2 diabetes risk factors include:
      • Obesity: Liver and muscle cells exhibit insulin resistance.
      • Age: Liver and muscle cells exhibit insulin resistance.
      • Family history: Inherited risk.
      • Blood lipid levels: High LDL and low HDL cholesterol levels.
      • Sedentary lifestyle: Physical activity controls weight, utilizes excess glucose, and maintains insulin sensitivity in liver and muscle cells.

    Excretion

    • Excretion is the removal of metabolic waste, toxic substances, and substances in excess of the body’s needs.
    • Excretion is essential because metabolic activities produce harmful or toxic substances that are not required by the body.
    • Metabolic waste/excretory products must be removed from the body.

    Osmoregulation

    • Osmoregulation maintains a constant water potential by controlling the water potential and solute concentration in the blood involving the kidneys and skin.
    • Excess amino acids are deaminated to urea in the liver.
    • Ultrafiltration: High blood pressure in the afferent arteriole, larger than the efferent arteriole, forces small, soluble substances like water, urea, and amino acids into Bowman’s capsule to form glomerular filtrate.
    • Proximal convoluted tubule: Amino acids and glucose are selectively reabsorbed through diffusion and active transport from the glomerular filtrate.
    • Distal convoluted tubule and loop of Henle: Water and mineral salts are reabsorbed.
    • Collecting duct: Water is reabsorbed from the urine.
    • Formed urine is removed via the urethra.

    Eye

    • Sclera: Tough, white outer covering of the eyeball, continuous with the cornea. Protects the eye from mechanical damage.
    • Conjunctiva: Thin transparent membrane covering the sclera in front. Mucous membrane secreting mucus, keeping the front of the eyeball moist.
    • Eyelashes: Shield the eye from dust particles.
    • Eyelid: Protects the cornea from mechanical damage. Squinting helps prevent excessive light entry.
    • Tear gland: Secretes tears for various functions:
      • Washing away dust particles.
      • Keeping the cornea moist for dissolved oxygen diffusion.
      • Lubricating the conjunctiva, reducing friction during eyelid movement.
    • Iris: Controls pupil size, regulating light entering the eye.
    • Pupil: Hole in the center of the iris allowing light entry.
    • Ciliary body: Contains ciliary muscles, regulating lens curvature/thickness.
    • Suspensory ligament: Connective tissue attaching the lens edge to the ciliary body.
    • Aqueous humor/chamber: Maintains eyeball firmness and refracts light into the pupil.
    • Vitreous humor: Transparent, jelly-like substance behind the lens. Maintains eyeball firmness and refracts light onto the retina.
    • Cornea: Dome-shaped layer continuous with the sclera. Refracts light rays into the eye, causing the greatest refraction.
    • Lens: Elastic, changes shape/thickness for focusing light onto the retina.
    • Choroid: Middle layer of the eyeball. Contains blood vessels transporting oxygen and nutrients to the eyeball, and removing metabolic waste products. Pigmented black to prevent light reflection within the eye.
    • Retina: Innermost layer of the eyeball. Light-sensitive layer forming images, containing photoreceptors producing nerve impulses when stimulated and connected to the optic nerve. Nerve impulses are transmitted from the optic nerve to the brain.
    • Fovea: Small yellow depression in the retina. Where images are typically focused. Contains the highest density of cones but no rods, enabling detailed color vision in bright light.
    • Blind spot: Region where the optic nerve leaves the eye. Contains no rods or cones, not sensitive to light. Cannot see objects whose image falls on the blind spot.
    • Optic nerve: Transmits nerve impulses from photoreceptors to the brain when stimulated.

    Forming an image on the retina

    • The cornea and aqueous humor refract light rays onto the lens.
    • The lens further refracts and converges the light rays on the retina.
    • The image on the retina stimulates the photoreceptors.
    • The image formed is upside down, laterally inverted, and smaller.
    • Nerve impulses are produced by the photoreceptors and transmitted via the optic nerve to the brain.
    • The brain interprets these nerve impulses, allowing us to see the object upright, front to back, and in the correct size.

    Accommodation/Focusing

    • Adjustment of the lens to form clear images of objects at different distances on the retina.
    • Far object:
      • Ciliary muscles relax, pulling on the suspensory ligament.
      • Suspensory ligament becomes taut, pulling on the lens edge.
      • Lens becomes thinner and less convex.
      • Refracts light onto the retina to produce a focused image of the far object.
    • Near object:
      • Ciliary muscles contract, relaxing their pull on the suspensory ligaments.
      • Suspensory ligament slackens and becomes less taut, relaxing their pull on the lens edge.
      • Lens becomes thicker and more convex.
      • Refracts light onto the retina to produce a focused image of the near object.

    Pupil Reflex: Bright light

    • Circular muscles of the iris contract.
    • Radial muscles of the iris relax.
    • Pupil constricts to reduce light entering the eye, producing a focused image.

    Pupil Reflex: Dim light

    • Radial muscles of the iris contract.
    • Circular muscles of the iris relax.
    • Pupil dilates to allow more light into the eye, producing a focused image.

    Advantages of pupil reflex

    • Protective reflex.
    • Regulates light entering the eye, preventing damage to photoreceptors and ensuring optimal image formation.

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