sac 2 bio

levels of organisation in the human body

cell- tissue -organ-system-organism

cell

basic structural and functional unit of life.

tissue

A cluster of cells that perform a shared function

organ

A combination of tissues that form a structure that performs a specific function

system

a collection of organs and tissues that perform a specific function.

organism

•a living thing made up of one or more cells

specialised cell

a cell with features that allow it to perform a specific function

level of organisation- cells

Cells have different shapes for different jobs. They work together in tissues to do tasks that one cell alone can’t do.

level of organisation - tissues

Cells of the same type work together to form a tissue and do a specific job. Tissues form organs, and organs work together in systems that keep the body aliv .

what are the 4 main tissues in animals

•Epithelial

•Muscle

•Connective

•Nervous

level of organisation -organs

•An organ is a collection of tissues working together to form a particular function (organs make up organ systems)

level of organisation - systems

A system is a group of organs working together to do a major job. Systems depend on each other to function properly.

Digestion

•the process of breakdown of large food molecules into smaller forms that can cross the plasma membrane and be used by the body.

4 main steps in digestion

Ingestion, digestion , absorption , egestion

ingestion

food is taken into the body. the teeth, saliva, and tongue play an important role in ingestion. The teeth physically break down food into smaller pieces, whilst enzymes in the saliva chemically break down the food pieces into a soft mass that can be swallowed

mouth ingestion

chemical-Saliva is an example of a digestive juice as it contains enzymes such as amylase and lipase which helps digest the food and starts to  break down carbohydrates and fats. It also makes it easier to swallow

mechanical -Putting food in your mouth is called ingestion. Your teeth break it into smaller pieces and mix it with saliva from your salivary glands

digestion

•food travels along the digestive tract and is broken down physically and mechanically by a range of organs..

oesophagus

When you swallow, food goes into the oesophagus that is mixed with saliva which is called a bolus. Muscles push it down the pharynx into the esophagus where muscular contractions known as peristalsis move it down towards the stomach

stomach digestion

mechanical - Stomach muscles break food down and push it to the small intestine. This mixing movement is called churning.

chemical-In the stomach, food is mixed with acid and digestive juices. Hydrochloric acid and enzymes (like pepsin) help break down proteins and prepare nutrients for absorption.

absorption

•digested food is absorbed across the plasma membrane of cells in the digestive tract into the bloodstream.

small intestine absorption

mechanical - Peristalsis occurs to push the food along the length of the small intestine

chemical-in the small intestine, digestive juices, bile, and pancreatic enzymes help break down food further. This is where digestion is completed and nutrients, minerals, and small food molecules are absorbed into the bloodstream.

large intestine absorption

Undigested food (like fibre) moves into the large intestine, where water is absorbed to form solid faeces. Peristalsis then moves this waste along the intestine for elimination.

Egestion

elimination of undigested food as faeces

2 methods of food digestion

physical/ mechanical digestion and chemical digestion

physical/mechanical digestion

•the process of breaking down food into smaller pieces. It increases the surface area for enzymes to act upon. Key processes include chewing (mastication) in the mouth, churning in the stomach, and segmentation in the small intesti

chemical digestion

food pieces undergo chemical digestion by enzymes and stomach acid, producing smaller molecules that are capable of being absorbed

physical or mechanical digestion

starts in our mouth where to be absorbed, food must first be broken into smaller pieces for digestion.

enzymes

split larger molecules into smaller molecules

The three major types of digestive enzymes

amylases, proteases, and lipases

amlyases

found in human salivary glands where it breaks down starch into sugars.

protease

Produced in the stomach and pancreas, these enzymes break down proteins into amino acids for tissue repair and cell building.

lipases location

pancreas which secretes it into the small intestine to break down fats.

liver

The liver has many jobs, including controlling metabolism, removing toxins, and processing nutrients. During digestion, it makes bile, which helps break down fats. Bile is stored in the gall bladder and released into the small intestine when needed.

pancreas

The pancreas produces digestive enzymes (amylase, protease, and lipase) that are released into the small intestine and activated in the duodenum. It also secretes bicarbonate to neutralise stomach acid, creating the right conditions for these enzymes to work effectively.

surface area and absorption in small intestine

The small intestine allows more nutrients to be absorbed through the intestine by creating a massive internal surface area within a narrow tube. This is achieved through circular folds, finger-like villi, and microscopic microvilli on epithelial cells

Rectum and Anus

Next the faeces passes into the rectum where it is stored. It is then pushed out of the anus in a process called egestion. It takes roughly 24-48 hours for food to go through the entire digestive system

three cell types of the digestive system and state their function

Parietal Cells - Chief Cells- Mucous Cells

Parietal Cells

These cells secrete hydrochloric acid (HCl), which lowers the pH of the stomach to kill bacteria and break down food

Chief Cells

Found at the base of gastric glands in the body and fundus of the stomach. They Secrete pepsinogen and gastric lipase.

Mucous Cells

These cells secrete a thick, alkaline mucus that protects the lining of the stomach from the harsh hydrochloric acid

  What is the function of peristalsis?

moves food, liquids , and waste through the digestive system