Human Biology: Digestive System

Unit 5: Human Biology

• The unit covers the human digestive, circulatory, lymphatic, breathing, excretory, and immune systems, along with renowned Ethiopian physicians
• Learning competencies include discussing structure and function, classifying types of digestion, listing end products, expressing absorption sites, exploring adaptations, differentiating routes, grouping enzymes, demonstrating heart structure, differentiating circulations, comparing arteries/veins, debating blood donation, discussing lymphatic system, defining immunity, relating systems, discussing diseases, drawing systems, showing links, demonstrating breathing, designing models, and examining smoking effects

5.1 The Digestive System

• All living organisms need nutrients to survive
• Plants obtain nutrients from their roots and energy through photosynthesis
• Animals obtain nutrients by consuming other organisms
• Biological molecules necessary for animal function: amino acids, lipid molecules, nucleotides, simple sugars
• Animals must convert macromolecules into simple molecules through digestion and absorption

Digestive Processes

• Ingestion: Taking in of nutrients, in the mouth
• Digestion: Breakdown of complex molecules into smaller components by enzymes, begins in the oral cavity and extends to the small intestine
• Absorption: Transport of digested nutrients from the small intestine to body cells, through villi in the small intestine
• Egesting: Removal of food waste from the body

Human Digestive Tract

• Digestive tract of adult humans is 6.5-9m long
• Stores and breaks down organic molecules into simpler components
• Physical digestion begins in the mouth, where food is chewed and formed into a bolus by the tongue
• Physical digestion increases the surface area for chemical digestion
• Chemical digestion of carbohydrates starts in the oral cavity with salivary amylase (ptyalin)
• The food goes down the esophagus, a long tube connecting the mouth to the stomach

Inside the Stomach

• The stomach uses peristalsis, wave-like smooth-muscle contractions, to push food
• Stomach acidity kills microorganisms, breaks down food tissues, and activates digestive enzymes
• Chemical digestion of protein starts in the stomach with the enzyme pepsin
• Further breakdown occurs in the small intestine
• Bile (produced by the liver) and enzymes (produced by the small intestine and pancreas) continue the process of digestion
• Smaller molecules are absorbed into the bloodstream through the epithelial cells lining the walls of the small intestine

The Oral Cavity

• Both physical and chemical digestion begin in the oral cavity
• Point of entry for food into the digestive system
• Food is broken into smaller particles by mastication (chewing)
• Saliva produced by salivary glands contains amylase enzyme, breaking down starches into simpler molecules
• Saliva dissolves food particles, lubricates food for swallowing, and allows us to detect flavor
• The tongue positions and mixes food, forming a bolus for swallowing

Structure and Types of Teeth

• The teeth are important structures for physical digestion
• There are 4 types of teeth:
• Incisors: Chisel-shaped teeth at the front of the mouth specialized for cutting
• Canine: Sharp, dagger-shaped teeth specialized for tearing
• Premolar: Broad flattened teeth specialized for grinding
• Molars: Broader teeth designed for crushing and grinding food
• Wisdom teeth, the last set of molars, usually emerge around ages 16-20
• Enamel is covering each tooth, which is the hardest substance in the human body

Anatomy of Teeth

• Enamel: Hardest, white outer part of the tooth made of calcium phosphate
• Dentin: Layer underlying the enamel containing microscopic tubes
• Pulp: Softer, living inner structure of teeth, containing blood vessels and nerves
• Periodontal ligament helps to hold the teeth tightly against the jaw
• Roots extend into the bone and hold the tooth in place, making up approximately two-thirds of the tooth
• Gums (gingiva): Fleshy, pink connective tissue attached to the neck of the tooth and the cementum
• Crown: Top portion of the tooth that is visible

Human Dentition

• Conventional way of expressing teeth number: incisor(I), canines(C), molars(M) and premolars(P) (I:C:P:M)
• Example: 2:1:2:3 for upper teeth means 2 incisors, 1 canine, 2 premolars and 3 molars on one side
• Dental formula of human beings (adults): (2123 / 2123) × 2 = 32
• There are 2 types of dentition: temporary and permanent
• 20 teeth in the temprorary and 32 teeth in the permanent formation
• Milk teeth (deciduous teeth): In a child there are 20 teeth, they grow at age 6

Keeping Teeth Healthy

• Adult teeth should last a lifetime affected by bacteria that cause dental caries and periodontal disease
• Regular brushing and dental checkups is helpful, and reducing sugar intake
• Acid attacks dissolve enamel and dentine, leading to tooth decay, with intake of acidic food may weaken it

Passage to the Stomach

• The swallowed food (bolus) travels from the mouth to the stomach through the esophagus

The Stomach for Digestion

• The stomach is the site of food storage and initial protein digestion
• It contains three layers of muscle for churning food
• Movement of food to and from the stomach is regulated by circular muscles called sphincters
• Contraction of the lower esophageal sphincter (LES) closes the opening to the stomach protecting against regurgitation

Regulating Food Movement

• second sphincter, the pyloric sphincter: Regulates the movement of food and stomach acids into the small intestine
• The movement to and from is regulated by circular sphincters
• Sphincters act like drawstrings on a bag, contraction closes opening while relaxation allows food to enter
• The lower esophageal sphincter prevents food and acid from being regurgitated up into the esophagus
• pyloric sphincter: Regulates movement into the small intestine
• J-shaped stomach: Numerous ridges that allow it to expand and is able to store about 1.5L of food, with millions of cells lining its inner wall

Activities occurring in the stomach

1. Cells secrete various stomach fluids (gastric fluids or gastric juice) to aid digestion
2. contractions mix food with gastric fluids
3. Physical (churning) and chemical digestion (e.g., protein digestion by pepsin)

• Approximately 500mL of fluids are produced after a large meal
• Gastric fluid includes mucus, hydrochloric acid, pepsinogens, and other substances
• Hydrochloric acid kills harmful substances, converts pepsinogen into pepsin (protein-digesting enzyme)
• Pepsin breaks long amino acid chains into shorter chains (polypeptides)
• pH inside the stomach normally ranges from 2.0-3.0 but may approach 1.0
• High acidity of hydrochloric acid kills pathogens and enables pepsin

Stomach Protection

• A layer of alkaline mucus protects the stomach lining from being digested from the acids
• Pepsinogen is being activated by the hydrochloric acid (HCl) to become pepsin, then begins to to break down the proteins
• Mucous layer protects the the stomach's own proteins
• If the lower esophageal sphincter is weak, stomach acid causes heartburn
• Partially digested food and gastric juice mixture is called chyme

Absorption

• Stomach absorbs glucose/simple sugars, amino acids, fat-soluble substances, water, specific vitamins, alcohol

The Small Intestine

• Is 7m long but only 2.5cm in diamter and performs the most chemical digestion
• The duodenum (first 25-30cm), jejunum, and ileum are three parts
• Enzymes are secreted and contents are moved by the small intestine
• Stomach absorbs vitamins, medicines, and alcohol, but the most absorption occurs is absorption Long finger like projections occur for surface area, called villia
• Microvilli: Fine, threadlike extensions of the membrane, further increase the surface for absorption of nutrients in the body
• One villus is supplied with a capillary network that intreweaves with other vessels (lacteals) to transport materials all across the tissue There are organs that enhance the body by adding secretions and enzymes

Accessory Organs

• Organs that add secretions and enzymes that break down nutrients
  • Salivary glands
  • Pancreas
  • Liver
  • Gall Bladder
• Secretions of glands are regulated by hormones in response to food consumption, the largest organ of the body, is responsible for bile production and detoxification of blood bile: Digestive juice required for fat digestion in teh duodenum
• Liver processes absorbed vitamins/fatty acids and synthesizes plasma proteins
• Gall bladder stores bile/concentrates bile salts

The Role of the Pancreas

• The pancreas has secretions that contain enzymes that will promote fat, carbohydrate and protein breakdown Trypsin: The digestion of protein is trypsin, which is released from the pancreas and enters the small intestine. It is released by trypsinogen (inactive)

• once Trypsinogen reaches the small intestine, enterokinase (enzyme ) converts the inactive version to inactive, which act on partially digested proteins) ,which breaks down polypeptides (long chain) to short peptide chains

• Erepsins are also a factor that works to digestion complete by pancreas from short changes creating amino acids

• Amylase: Continues by digestion of carbohydrates which was started in the mouth

  • Disaccharides: break intermediate sized chains in order to digest by the small intestine

Liver and Gall Bladder

• Bile fluid production by liver, containing components (bile salt) which aid in all of fat digestion the gall bladder concentrated (storing of bial) happens when the empty stomach occurs
• release of fats occurs into the small intestine, release of fats is produced for hormones by gallbladder to create bile salts

Inside the the Small Intestine

• Emulsification (breaking down large fat) happens once inside
  • Not actually chemical due to chemical bonds not broken and large to smaller breakdown
• Fat prepares chemical digestion via surface area increasing bile - Also possesses pigments, The breaking then storage of red breakdown products occurs with the gall bladder removal from the liver

The Large Intestine

• The human intestine is smaller length by larger diameter
• three small parts cecum, rectum and colon Colon regions consist of:
  • ascending
  • transverse
• descending
• sigmoid colon
• The primary colon purposes include mineral/water absorption and long term waste storage
• synthesis by Vitamins b and K happens by E.coli for use of waste materials is conducted within the large synthesis
• water is able to reasborb it from the colon due to it having the ability to store

The Lymphatic System

• Is the system that the returning all proteins too the body that were spilled out
• Lymph similar plasma, with open ends/valves
• lymph nodes contains what blood cells that filteer out any bacteria

The key roles

• interstitial fluid return too body absorbed fats/ vitamins from lipid digestive processes has defence for bodies microorgans

Lymphatic trunks join to lymphatic ducts(two parts): The thoracic duct (remainder) and the light lymphatic duct (quadrant part)

Lymphatic : thin walls with valves to prevent from reflux, the pressures caused by skeletal action muscle

Lymphocytes created from alongside bone marrow. (red/transpoprted via lymphatic organs)

Heart System

A heart or the heart and blood systems (also known as cardiovascular is the same or has link,

Heart includes endocardium, myocardium and epicardium and it has 4 chambers with many valves, with the cardiac system controlling blood flowing Pulmonary and systolic are linked with two circuits , Oxygen depleted causes blood to go right atrim to interior venas cave. while pulmonory is a movement to the heart lung with a double blood double path

• arteries break into smaller arts (aterioles)with a gas exchange

• systolic blood pressure less 120 , mmgh with diastlic under 80 mmgh when reading bp

• vessel help distrubute body tissues w pulmonary and systolic paths creating a tube path. This leads to capillaries, atieries and veins.

Platelets + Blood Clotting Blood consists of 8 percent of body , with 3 factors the cell components (which transport bodies gas), white blood, ( fight infection) and smallest cells ( platelets) and finally (red blood erythocytes) Blood does 40 to 50 from full body with gas protein (haemoglobin) for oxygen. The lack if defiecny causes feelings of fatigute

The adaptations to blood

• small cell (for heamoglobin)
• biconcave allows diffusion
• cell surface allows rapid c02 and 02

• platelets + white blood cells with infection defence these cells ( leaukcytes) create responses such as fighting for removal. Neutrophills or lymphocyres Platelets help prevent disease when coming to clot blood.

Blood Group+ Rhesus Factor

Antigens ( protiens &blood) with the blood group that contains on the 2 cell group type 1 abo 2 rh If blood transfers in the system.

The ABO group includes A, B, AB, 0

• rhesus negative can ddonate but cannot retain from other if aby interits + factor from father erthroblasts fetalis

Blood Donations Factors

3 Main Topics For Donators

• the donation reason
• outline reasons
• blood factor

Lymphatic System (cont)

Lymph nodes. With bacteria, with white blood etc it will also store lymphocytes which prevent damage

main key parts include :

• interstitial fluid with return to blood

• absorbtion of fats and liposoluble parts via digestive path

• defense of disease

• lymph: vessels and fluid within the bone marrow.

5.3 The Breathing System

• To breathe, cells require oxygen to run the oxidative stages of cellular respiration (ATP)
• Carbon dioxide drives our need for breathing which is released for waste
• The respiratory system consists: • Muscles for moving air • Passageways that transfer Air • Microscopic has surface for capillaries

System has to. Coordinate 02 intake with carbon duioxide that can be achieved

System path is via nose (nostris-> pharynx and receving for inahlation -> trachea to larynx) Main nasal structures:

• Nosterils( main entry and exit)

• septum ,receives air for inhalation with mucous for the memmberanes. These create a filter from air and are the air systems of good condition.

Throat (phayrynx and larynx) lift up for swalling to avoid to switch the system which creates more region when food travels

Larynx is cartilage part and regulates the long travel. Is an opening to a trachea (windpipe), where trachea forms for cartliage stacking by connects. Memmberanes strecth with elasticity. Also contains Bronicholes

Finally alveolar leads gas parts. Inalvear the is to breath and increase are when air gets in. This is an active transport when atmospheric with a muscle for pressure volume and lungs for diaphgram.

Inhilation + Other System Factors

• Intercostals system create upward rib pull due to the low atmospheric vs pressutre air travels in

with air we get o2 and expell air with carbon duioxide!