Digestive and Excretory systems

Section 30.1 Organization of the human body

How is the human body organized? •Cells of the human body are organized into different levels•Different parts of the body work together to carry out specific

functions

How many different types of tissues are there? What do they do?

•Connective tissue: Provides support for the body, and connects it’s parts

•Epithelial tissue: Lines interiors and Exterior body surfaces

•Nervous tissues: transmit nervous tissue through the body – neurons and glial cells

•Muscle tissue: make up muscles

How many different human body systems are there? What do they do?• In addition there is

also the integumentary system – skin, hair and oil glands

What is homeostasis?

When else have we come across negative feedback?

What does the liver do? What role does the liver play in homeostasis? • The liver produces bile – which aids in the digestion fat• But it also has a number of other functions….• The liver converts ammonia to urea• Converts dangerous compounds, such as drugs, into

compounds that can be removed from the body safely• Regulates the level of glucose in our blood stream

• Both takes it out and releases glucose as/when needed

• Abnormally high glucose levels are associated with diabetes• Due to changes in the pancreas or body cells that affect the

cell’s ability to absorb glucose• Diabetes is the result of one of the failure of homeostasis with

respect to blood glucose levels

Key concepts

•Why is the human body often described as complex and organized?

•What are the four types of tissues?

•What is homeostasis?

•How is a home heating/cooling system similar to how a human maintains body temperature?

•What roles does the liver play in maintaining homeostasis?

Food and nutritionSection 30.2

Why shouldn’t you eat this every day?

Why do humans need to eat?

• For Energy!

• Food contains the basic molecules that can be use to build ATP

• Food supplies the raw materials your body needs to build and repair tissues • Food contains at least 45 substances

that the body needs, but does not manufacture

• A healthy diet ensures that your body receives all of these required substances

How do you measure the amount of energy in food? •You burn it

•One calorie is the amount of heat needed to raise the temperature of 1 gram of water by 1 degree Celsius

•One dietary Calorie is equal to 1000 calories, or 1 Kilocalorie

What nutrients does your body need?

•Water

•Carbohydrates

• Fats

•Proteins

•Vitamins

•Minerals

Why is water important?

• Every cell needs water, because many of the body’s chemical reactions take place in water

• Water makes up blood, extracellular fluid and other bodily fluids

• We loose water as sweat, urine or when we breathe

• Humans on average need to drink at least 1 liter of water a day to replace what is lost • In Arizona we need to drink a lot more than

this – why?

• If the body does not get enough water, it can lead to dehydration, which under certain conditions can be fatal

Why do you need to eat Carbohydrates?

• Simple and complex carbohydrates are a major source of energy• Sugars found in fruits, honey and sugar cane are simple

carbohydrates• Starches found in grains, potatoes and vegetables of

complex carbohydrate, or polysaccharides

• The digestive system breaks down starch into simple sugars

• Excess blood sugar is converted into glycogen, which is stored in the liver and skeletal muscles • Excess sugar can also be stored as body fat

• Fiber is also a type of complex carbohydrate – cellulose? Why is Fiber important?

• Our bodies can not break down fiber, but it’s presence help move things along the digestive system

Is it always bad to eat Fat?

• Not always - Fats help the body absorb fat soluble vitamins, and are a part of cell membranes, nerve cells and certain hormones

•What is the structure of a fat? What is the difference between a saturated and an unsaturated fat?

•Many unsaturated fats are modified by adding hydrogen to them – trans fats

• This increases the shelf life, but may have some serious health related side effects

Why do many people who work out with weights eat protein bars/drink protein shakes?

• Proteins supply the raw materials for growth and repair of structures such as skin and muscle

• Many enzymes are proteins – why are enzymes important?

• What role do proteins have in transport across cell membranes?

• Hormones can be protein - such as insulin

• Hemoglobin is a protein – what does this protein do?

• Proteins can even be used as an energy source when others are in short supply

• What are proteins made of?

• Only 12 of the 20 amino acids can be made by the body – the other “essential 8” must be consumed • Meat, fish, eggs and milk are important sources of

protein

What role do vitamins and minerals play in the body?

• Vitamins are only needed in small amounts, but help perform chemical reactions• The tools that help put the building blocks together

• Two types of vitamins – fat soluble and water soluble • Only fat soluble can be stored in the body

• The body also needs a number of minerals in small amounts• Calcium, is needed to produce calcium phosphate that makes up bones and teeth• Iron needed for hemoglobin

• Constant supply needed to replace those lost in sweat, urine and digestive waste

What should you look out for on a food label? • Fats have more Calories than

proteins and carbohydrates due to the extra C-H bonds in carbohydrates or proteins

•Remember, percent daily values are based on a 2000 Calorie diet

•An active, male teenager will often need about 2800 Calories a day

Why does America (and a number of other Western Countries) have a growing obesity problem?

• Inactive lifestyles and a high calorie diet

• The American Heart Association recommends a diet with a maximum of 30 % of calories from that, of which only 7 % from saturated fats, and 1% from trans fats

•Whose job is it to improve the health of a country? Should governments push healthy eating on the population, should insurance companies charge higher premiums to overweight people? Should people be left to eat what they want, as it is their own bodies……. ?

Writing assignment

• Should schools offer only healthy food choices in the cafeteria and in vending machines? What are other ways that schools and governments can encourage healthy food choices and physical activity

Key points

•What are the two main reasons humans need to eat?

• Foods that contain many calories but few raw materials are said to contain empty calories – what do you think the phrase empty calories means?

•What six nutrients does the body need?

•How are saturated and trans saturated fats similar, how are they different?

•What is meant by a balanced diet? How can food labels be use to plan a balanced diet?

The Digestive SystemSection 30.3

What is the main purpose of the digestive system?

•The digestive system converts food into small molecules, that can be used by the cells of the body

•There are four stages

• Ingestion - eating

•Digestion – Mechanical and chemical

•Absorption – occurs in intestines, absorbed into circulatory system

•Elimination – all waste material removed as feces

Why is the mouth important? • Teeth do most of the mechanical digestion

• Incisors, cuspids and bicuspids grind at food• Molars grind and crush food• Tongue moves food around

• Saliva triggered by the scent of food (controlled by nervous system)• Contains Amylase – breaks down starch• Also contains Lyzosome – helps prevent infection by

breaking down bacteria

• Tongue and throat muscles force clumps of food (bolus) down into throat• Flap of connective tissue – (epiglottis) prevents food

entering trachea

What is the esophagus?

•The esophagus connects the mouth to the stomach

•Does gravity force food down?

• If so, how would astronauts eat in space?

•Peristalsis provides the force that drives food into the stomach

•Cardiac Sphincter closes the esophagus from the stomach

•What is heartburn?

What is the pH of the stomach? What is it designed to digest?

• Very acidic due to hydrochloric acid

• Enzyme pepsin breaks down proteins

• Glands produce mucus which protects the stomach wall - if it fails, can lead to a peptic ulcer

• Stomach also causes mechanical digestion due to alternating contractions – essentially churning• Chyme produced (oatmeal conistency)• After a few hours, the pyloric valve opens up,

and chyme is released into small intestine

What are the roles of the pancreas, liver and gallbladder in digestion?

• The pancreas produces hormones that regulate blood sugar level,

• It also produces enzymes to help break down carbohydrates, proteins, lipids and nucleic acids

• It also produces a sodium bicarbonate – a base. Why do you think a base is needed at this stage of the digestive system?

• Enzyme would be destoryed by stomach acid – it needs to be neutralized

• The Liver assists in fat digestion

• Liver produces bile, a fluid loaded with lipids and salt, which is stored in the gallbladder

• When fat is present in the duodenum, the gallbladder releases bile into the small intestine

• Fat globs together, making digestion difficult. Bile breaks up these globs

So where are different enzyme found in the digestive system? What do they do?

How does absorption from the small intestine work? • Most nutrients from food are absorbed

through the small intestine

• After leaving the duodenum, most chemical digestion is finished

• Small intestine designed for absorption of food – how?

• Villi and microvilli move move and absorb food particles

• Products of carbohydrates and proteins absorbed by capillaries in the villi

• Fats and fatty acids are absorbed by lymph vessels

• At the end of the small intestine, only water, cellulose and other indigestible substances are left behind

What does the large intestine do? • Before entering the large intestine, material

passes by the appendix. What is the role of an appendix?

• Chyme then enters the large intestine/colon• Primary function is to remove water from

undigested material - this process happens quickly

• Colonies of bacteria help produce compounds that the body can use, such as vitamin K• Antibiotics can inadvertently destroy these colonies

• Feces eliminated through the anus• Issues with water removal can lead to diarrhea

or constipation

Key points

•What is the function of the digestive system?

•What is the difference between mechanical and chemical digestion?

•What structures does food travel through during digestion? What are their functions?

•What would happen if your stomach could not contract and churn food?

•How are nutrients absorbed?

•Why are villi folded?

The excretory systemSection 30.4

What waste products do our bodies produce?

•Our body generates a lot of waste as part of it’s every day function• Excess salt• Carbon dioxide

• Ammonia is one of the most toxic waste compounds produced – how?• It is produced when amino acids from

proteins are used for energy• It is converted to Urea, which is less toxic

but still needs to be eliminated• The body uses skin, the lungs, the liver

and kidneys to eliminate excess waste

How does a kidney work?

• Kidneys are essentially natural filters

• Blood enters through renal artery

• Kidney removes Urea, excess water and minerals, and other waste products

• Clean filtered blood leaves through renal vein

• Blood purification takes place at nephrons – kidneys have nearly a million

• Involves two steps – Filtration and Reabsoprtion

What is the difference between Filtration and Reabsorption?

• Filtration is when a liquid or gas is passed through a filter to remove waster

• This takes place in the Glomerulus• A small dense network of capillaries encased in the upper end of each nephron in a

hollow structure called a Bowman’s capsule

• Bowman’s capsules and wall of capillaries are permeable• Fluid flows into bowman’s capsules• Filtrate (material that is filtered) contains water, urea, salt, glucose, amino acids and

some vitamins• Large substances such as blood cells and proteins are too large to pass through

capillary wall

• Most of the material that passes through the Bowman’s capsule re-enters the blood - Reabsorption

• 180 liters of filtrate pass through nephron tubules each day• Much of the filtrate (salts, vitamins, amino acids, fats and glucose) are removed

from the filtrate by active transport• Water follows by osmosis

• Essentially, nearly everything is thrown away, but then the body reabsorbs what it needs

• Loop of Henle conserves water and minimizes filtrate, before passing material on to the collecting ducts, ureter, and ultimately bladder.

What role do the kidney’s play in homeostasis?

•Kidneys Remove waste, maintain blood pH and regulate water content – they respond directly to the composition of the blood (with some help from the endocrine system)

•Your pituitary gland will release Antidiuretic hormone into your blood if you have not drunk enough fluids• Tells the kidneys to reabsorb more water

and excrete less into urine

What can you learn from urine?

•Not only does the color tell you how dehydrated you are, but your urine can store a lot of other information

•Presence of protein or glucose can be an indicator of a serious disease/disorder such as diabetes or high blood sugar

•Urine samples are often used for drugs tests, as drugs remain in the filtrate

What happens if a kidney doesn’t work properly?

• Kidney stones – when a ureter gets blocked due to calcium, magnesium or uric acid crystalizing in urine. Can be treated with ultrasound waves

• Kidney damage – often related to high blood pressure and type I diabetes• High blood pressure damages filtering mechanism• High blood sugar levels results in increased filtration and more

strain• Can lead to kidney failure

• Kidney Failure – two options: Dialysis or transplant• Dialysis is when a machine essentially performs the job

of a kidney• Needs to be done 3 times a week, 4 hr sessions, and patients

have restricted diet

• Transplant – complete replacement• A person can survive with only one kidney!

Key concepts

•What organs are involved with excretion?

•Why is excretion important for homeostasis?

•What substances do kidneys remove from the blood?

•What happens during filtration, reabsorption and urine excretion?

•How do kidneys help maintain water balance?

•Why are protein or glucose in urine a sign of kidney damage?