Table of Contents

Introduction

Digestive and Urinary Systems

Part A

i) Parts of the Digestive System

ii) Functions of Digestive System

iii) Macronutrients

Introduction

Digestive and Urinary Systems

Part A

The Digestive System consists of a group of organs that work together to change food into energy along with basic nutrients that feed the whole body.  It breaks down nutrients into parts small enough for the body to absorb them. Waste products are expelled from the body as faeces. Digestion starts at the mouth and the process ends at the anus. The Digestive System co-ordinates the movement of food together with cells that produce hormones and enzymes which aids the breakdown of food.

Hormones

Hormones are chemical messengers secreted by glands directly into the bloodstream and travel to the target organs (the organ that’s requires them). They influence metabolism, reproduction, growth and development.

Enzymes

Enzymes are proteins which speed up chemical reactions in the body. They breakdown food into small particles so that they can be digested and absorbed by the body.

Organs of the Digestive System

The organs of the digestive system can be divided into those of the (1.) Gastrointestinal Tract and (2.) Accessory Organs.

1. The Gastrointestinal Tract is also known as the Alimentary Canal. It is made up of hollow organs as follows;

• Mouth
• Pharynx
• Oesophagus
• Stomach
• Small Intestine
• Large Intestine

2. The Accessory Organs also play a vital role in helping your body digest food. The accessory organs are as follows;

• Teeth
• Tongue
• Salivary Glands
• Gallbladder
• Liver
• Pancreas

Functions of the Digestive System

The main functions of the Digestive System include the following processes:

• Ingestion – taking food into the Gastrointestinal Tract
• Propulsion – moves the food along the digestive tract through peristalsis and segmentation. Peristalsis is involuntary, it is a wave like movement of muscles contracting and relaxing which moves the food along the tract. Segmentation moves food back and forth transversely within the internal walls where it is mixed with digestive juices. Segmentation is more of a mechanical process other than of propulsion.
• Digestion is divided into:
  • Mechanical Breakdown – physical action of mastication (chewing) and segmentation (churning food in the stomach).
  • Chemical Breakdown – food is broken down into smaller parts by actions of enzymes in the body. Lipase breaks down Fats. Amylase breaks down Carbohydrates. Pepsin breaks down Proteins.
• Absorption – this is where the end products of digestion are absorbed into the capillaries in the blood and lymph.
• Elimination – this is where indigestible deposits of food are excreted as faeces by the bowel.

(i)       Parts of the Digestive System

(ii)            Functions of Digestive System

1. Mouth – is a muscular organ and its purpose is to prepare food for further digestion (Stomach and small intestine) it is also responsible for taste. It is the entryway of the Digestive System. When food enters the mouth it is chewed and broken down into smaller pieces. The front teeth cut and tear the food (incisors and canines) the back teeth crush and grind the food (bicuspids and molars). The food is mixed with saliva and moved around by the tongue and forms a pulp. The tongue then passes the pulp (bolus) down the throat into the oesophagus.

2. Oesophagus – is a muscular tube, 25cm long approx., it has a valve at each end called a Sphincter. Its function is to transport food and liquid from the pharynx to the stomach. Food which is now pulp (bolus) is pushed along here by peristaltic action (wavelike contraction of the smooth muscle tissue of the walls). Mucus is secreted by the oesophagus which lubricates the passage of food. No absorption takes place here.

3. Liver – is the largest internal organ and largest gland in the body. It weighs approx. 3.5lbs. It has a soft reddish brown colour and is triangular or wedge shaped. It is located under the diaphragm, above the stomach on the right side of the abdomen. The liver has the capacity to regenerate itself.

It has many functions:

Removes

• Harmful substances and toxins from chemicals, drugs and alcohol.
• Nitrogen and Amino Acids

Stores

• Glycogen and Iron
• Vitamins A, B12, D, E, K

Produces

• Heparin – an anti-coagulant
• Bile
• Thrombopoietin – Platelet formation
• Heat – it is the body’s radiator
• Vitamin A – from Carotene (found in green leafy vegetables and carrots)
• Vitamin D – the first stage of Vitamin D synthesis within the body takes place in the liver (Healthy Eating, 2018)
• Plasma Proteins
• Uric acid and urea from the breakdown of red blood cells and amino acids

Converts

• Metabolism of proteins
• Glycogen to glucose when energy is needed
• Glucose back to glycogen when insulin is present
• Stored fats (saturated) into cholesterol

4. Stomach – is a C shaped organ, it has layers of muscle fibres that expand and contract. It is lined with a mucus membrane and contains folds called Rugae. It expands when full and contracts when empty.

It is a temporary storage area for food. It churns food (chemical digestion) with gastric juices **. The mucus membrane produces mucus to help lubricate food. It absorbs alcohol directly into the bloodstream. It digests protein through the action of enzymes (chemical digestion). It also forms a thick liquid called Chyme. Chyme is squirted from the stomach into the first part of the small intestine (duodenum).

Gastric glands secretes gastric juices/enzymes as follows: **

5. Gallbladder – is a hollow pear shaped sac attached to the liver by cystic and bile ducts. It’s located under the liver in the upper right hand side of the abdomen. It is a storage area for bile, bile is made in the liver, but is stored in a concentrated form in the gallbladder until needed. It delivers bile to the small intestine. Its lining is made up of many folds, the folds flatten out when it expands. The gallbladder is an ____________ Gland, as it secretes directly into the bloodstream and contains Ducts.

6. Pancreas – is a greyish pink long flat gland, is has a fish like shape. It weighs approx. 80g and is 6 inches long. It is located behind the stomach. The head of the pancreas connects to the small intestine (duodenum). It plays a key role in digestion and glucose control. It plays a role in the digestive system and endocrine system. It

It produces very important hormones – Insulin and Glucagon. It is both an Endocrine and Exocrine Gland.

Endocrine – produces hormones

Insulin

Glucagon

Exocrine – produces enzymes

Lipase

Trypsin

Amylase

http://www.innerbody.com/image/endo03.html

7. Small Intestine – is approx. 20 meters long. It is made up of 3 parts, Duodenum (1ft), Jejunum (3-6ft) and ileum (6-12ft).  90% of the digestive process takes place here. The walls (lumen) of the small intestine have many folds called villi and microvilli these tiny finger like projections increase the surface area of the small intestine. They contract and relax, and sway in order to come into contact with most of the contents of the small intestine. All food is moved through the small intestine by Peristalsis – Involuntary wave like contractions of smooth muscle of hollow organs which move food through the body.

Duodenum – C shaped hollow organ located below the stomach and curves around the pancreas.  It is the first part of the small intestine and the shortest. It connects the stomach to the Jejunum.  It continues the process of digestion which began in the stomach. Its primary function is to receive Chyme a combination of partly digested food and stomach acids into the Duodenum.  Mucus is also produced in the folds between the villi in glands called Crypts of Lieberkuhn, the mucus protects the duodenum from the acidic content of chyme. The duodenum also receives bile from the Liver and Pancreatic Juices from the pancreas to aid digestion of food. Bile emulsifies fats and aids in their digestion. Pancreatic juices work as follows: Trypsin breaks down Protein into Amino Acids, Pancreatic Amylase breaks down Carbohydrates into Monosaccharides and Saccharides, Lipase breaks down Fats into Fatty Acids. The spaces in between the villi in the duodenum

Jejunum – is a continuation of the small intestine from the Duodenum. It is the middle segment found between the duodenum and Ileum. The villi in the jejunum are tall and cylindrical. It is located in the upper left hand side of the body. It has a thick intestinal wall. It has longer straight arteries. It is red in colour. This is where the chemical digestion food is completed.

Ileum – is the final part of the small intestine and opens to the large intestine. The villi in the ileum are short and cylindrical. The ileum is located in the lower left hand side of the body. It has a thin intestinal wall. It has shorter straight arteries. It is pink in colour. The main function of the ileum is to absorb nutrients. Bile is also absorbed here, through the blood vessels in the intestinal walls it is returned to the liver. Peyers Patches

http://teachmeanatomy.info/abdomen/gi-tract/small-intestine/

8. Large Intestine – it is the last part of the gastrointestinal tract. It is 1.5meters in length. It begins on the right side of the abdomen and is draped around the small intestine. It is shorter than the small intestine but it is thicker in diameter. It is also known as the Colon or Large Bowel. The large intestine is made up of the Caecum, Appendix, Colon, Rectum, Anal Canal and Anus.

The functions of the large intestine are:

• Absorption of nutrients, salt, water and vitamins that remain in digestive waste.
• Secretion – secretes mucus which helps lubricate the passage of waste.
• Produces Vitamin – produces Vitamin K, this plays an important role in blood clotting.
• Breaks down undigested food using bacteria.
• Formation of Faeces – the undigested residue of food is formed here as Faeces.
• Storage of Faeces – the rectum is a temporary storage area for Faeces.

9. Appendix – it is located in the lower right hand of the abdomen. It is approx. 4inches long and has a diameter of about ¼inch.  It is a narrow pouch of tissue with a wormlike appearance. It consists of a tissue call Lymphoid Tissue which plays a role in the immune system. It is not a vital organ. Scientists are still debating as to what the exact function of the Appendix are. Appendicitis occurs as a result of inflammation of the appendix.

1. One theory is that it was used in the past by our ancestors to digest cellulose material from plant based products, which we no longer have a need for or use.
2. Another theory is that the appendix is used for or acts as a storage area for bacteria which are beneficial to our bodies during times of illness. These bacteria survive and rebalance our intestines once the illness has left our system.

http://www.innerbody.com/image/dige03.html

10. Rectum – is a short straight section of the gastrointestinal tract. It is approx. 12cm long.  This leads from the Colon to the Anus. It is a temporary storage area for faeces. It is usually empty and only receives the contents of the colon when faeces are ready to be expelled from the body from the Anus. Faeces are waste products from food combined with indigestible residues, dead blood cells, fatty acids, mucus and bacteria that are both living and dead. Faeces gets its colour from the pigment in bile called Bilirubin and from dead blood cells.

11. Anus – it is the final part of the large intestine, it begins at the bottom of the rectum. The anus is separated from the rectum by the anorectal line. It is the external opening where faeces are expelled/excreted from the body. The anus is surrounded by touch tissues called fascia. Fluid is released into the anus to keep the surface moist. The anus is held closed by the internal sphincter which is under involuntary control. The external sphincter is under voluntary control, this is the only part of the bowel that we have conscious control over.

(iii)       Macronutrients

Proteins, Fats and Carbohydrates are known as macronutrients. They provide energy for the body in bulk amounts. Carbohydrates and protein provide 4 calories per 1 gram while Fat provides 9 calories per 1 gram.

PART B

(i)            Animal Cell

Cells

Cells are the smallest living unit in the body, they are also the building blocks of the body. They are eukaryotic cells, this means that they have a true nucleus and have specialised structures called organelles.  Organelles work together to allow the cell to function, they a variety of functions (each with their own function) to perform such as enzyme and hormone production and also providing energy for the cell.

Cells relationship to the body

• A group of cells of similar type join to form tissue
• A group of tissues of related function join to form an organ (heat, lung, stomach)
• A group of organs of related function join to form a system (respiratory, digestive, vascular)
• A group of systems join together to form an organism – the human body

Organelle	Function	Diagram
Cell Membrane	The cell membrane surround the cell It protects and gives shape It is made of 2 layers – Proteins and Lipids It is Semi Permeable – allows some substances to move in and out of the cell [O2 and Glucose – IN, waste – OUT]
Cytoplasm	Cytoplasm fills the cell with a fluid matrix – jelly like substance It holds the organelles in place It provides water and nutrients to the cell Fluid matrix maintains the pressure inside the cell to ensure that the cell does not shrink or burst.
Nucleus	The nucleus is the brain of the cell It directs all the activity of the other cellular organelles It contains DNA and Chromosomes (genetic information)
Nuclear Membrane