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By: MasterstudentUM • 1 year ago
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BBS2041Case 1 – Faecal characteristics teach us a lot
Learning goals:
Case 1 Faecal characteristics
Brainstorm
P.S.:
• Carbohydrates, proteins and fats
• Pancreatic duct (ductus pancreaticus)
• Monosaccharides, disaccharides, polysaccharides
• Unsaturated fats, saturated fats, and triglycerides
• Tumours produce more lactate
• micronutrients
• Amylases, peptidases, lipases, brush border enzymes,
• Gastrointestinal tract
Learning goals:
1. Anatomy of the G.I. tract
1. Organs from start to finish
2. Functions of every organ
2. Digestion & absorption of Proteins:
1. Which organs digest what nutrients?
2. What enzymes are involved?
3. where do they end up?
3. Digestion & absorption of fats:
1. Organs involved?
2. enzymes involved?
3. where do they end up?
4. DIgestion & absorption of sugars:
1. organs involved?
2. enzymes involved?
3. where do they end up?
5. What happened in the case’s story?
1. what happened to the patients?
2. cancer in relation to macronutrients?
1
,LG1 – What is the anatomy of the GI-tract?
An overview of the Gastro-Intestinal (GI)-tract.
The digestive or GI-tract is the tract in which food is digested, absorbed and excreted. It
can be seen as long tube passing through the body. It consists of several organs that play a
big role in the digestion process, including: mouth, pharynx, oesophagus, stomach, small
intestine, liver, gallbladder, pancreas, large intestine Accessory organs of the GI-tract
include the teeth, tongue, salivary glands.
The primary function of the digestive system is to move nutrients, water, and electrolytes
from the external environment into the body’s internal environment. To accomplish this,
the system uses several processes:
▪ Ingestion is simply taking food into the digestive tract, usually via the mouth
▪ Propulsion, which moves food through the alimentary canal, includes swallowing,
which is initiated voluntarily, and peristalsis (an involuntary process). Peristalsis, the
major means of propulsion, involves alternating waves of contraction and relaxation
of muscles in the organ walls. Its main effect is to squeeze food along the tract, but
some mixing occurs as well. In fact, peristaltic waves are so powerful that, once
swallowed, food and fluids will reach your stomach even if you stand on your head.
▪ Mechanical breakdown increases the surface area of ingested food, physically
preparing it for digestion by enzymes. Mechanical processes include chewing, mixing
food with saliva by the tongue, churning food in the stomach, and segmentation, or
rhythmic local constrictions of the small intestine. Segmentation mixes food with
digestive juices and makes absorption more efficient by repeatedly moving different
parts of the food mass over the intestinal wall. Although mechanical breakdown is
sometimes referred to as mechanical digestion, historically the term digestion
applies only to chemical breakdown processes that utilize enzymes
▪ Digestion involves a series of catabolic steps in which enzymes secreted into the
lumen (cavity) of the alimentary canal break down complex food molecules to their
chemical building blocks
o Digestion is the chemical and mechanical breakdown of foods into smaller
units that can be taken across the intestinal epithelium into the body
2
,▪ Absorption is the passage of digested end products (plus vitamins, minerals, and
water) from the lumen of the GI tract through the mucosal cells by active or passive
trans- port into the blood or lymph
o Absorption is the movement of substances from the lumen of the GI tract to
the extracellular fluid (active or passive process)
▪ Defecation eliminates indigestible substances from the body via the anus in the form
of feces
▪ Motility is the movement of material in the GI tract as a result of muscle contraction
▪ Secretion in the GI tract has two meanings. It can mean the movement of water and
ions from the ECF to the digestive tract lumen (the opposite of absorption), but it
can also mean the release of substances synthesized by GI epithelial cells into either
the lumen or the ECF
3
, Digestion in the oral cavity (mouth)
One main function of the mouth is ingestion. The walls of the mouth are lined with
stratified squamous epithelium and is keratinized which means that it forms a kind of
barrier to protect the epithelium against invader. The different elements in the oral cavity:
▪ Lips and cheeks help to keep food between the teeth when someone is chewing.
Their core is skeletal muscle
▪ The palate forms the roof of the mouth and consist of two parts:
1) The hard plate forms rigid surface where the tongue can push the food against
while chewing
2) The soft plate is a fold formed out of skeletal muscle that can lose the
nasopharynx while swallowing
▪ The tongue which is made out of interlacing bundles of skeletal muscle fibers, there
are intrinsic and extrinsic muscles. The tongue contains receptors for taste.
▪ The teeth are important for chewing, making the food smaller (mastication), and
thereby increasing the surface area for enzymes out of salvia [mechanical digestion].
In mouth there is voluntary movement of food, while swallowing is involuntary
movement of food.
▪ Salvia is a complex hyposmotic fluid that contains water, ions, mucus, and proteins
such as enzymes and immunoglobulin. Salvia is important for: cleaning the mouth,
dissolving food chemicals (for tasting), moistens food and compacting into a bolus,
lubricating food to make it easier to swallow, providing protection against invaders
(Lysozyme is an antibacterial salivary enzyme, and salivary immunoglobulins disable
bacteria and viruses), containing enzymes that start the chemical breakdown
[chemical digestion]
1) Chemical digestion begins with the secretion of salivary amylase.
▪ Amylase breaks starch (polysaccharides) into maltose (disaccharides)
after the enzyme is activated by Cl- in saliva.
2) Saliva is secreted by three pairs of salivary glands (exocrine glands): sublingual
glands under the tongue, submandibular glands under the mandible (jawbone),
and parotid glands lying near the hinge of the jaw
▪ The parotid glands produce a watery solution of enzymes while
sublingual glands produce a mucus-rich saliva. Secretions from the
submandibular glands are mixed, with both mucus and enzymes
▪ Salivary glands are, with secretory epithelium arranged in grape-like
clusters of cells called acini. Each acinus surrounds a duct, and the
individual ducts join to form larger and larger ducts. The main
excretory duct of each gland empties into the mouth.
3) Salivation is under autonomic control and can be triggered by multiple stimuli,
including the sight, smell, touch, and even thought of food. Parasympathetic
innervation is the primary stimulus for secretion of saliva, but there is also some
sympathetic innervation to the glands.
4
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