2.1 Introduction
Food and nutrition are important to keep us healthy and meet the various demands of daily life. Inadequate quantity and quality of nutrition will eventually result in a deficiency state. It was at the beginning of the twentieth century that the science of nutrition began to garner higher interest and scientists began to investigate the amounts of nutrients required to prevent deficiency states. Before moving on to study the different nutrients and their functions in the body, it is important to understand the fundamentals about human anatomy and the biological processes that take place in it.
In this way, we will be better placed to understand the impact of each nutrient and its role in our wellbeing. Nutrition helps support chemical reactions in cells that provide energy. The endocrine system consists of glands and the hormones that they secrete. Hormones are crucial for a number of important functions in the body including growth, sexual function, metabolism and heart rate.
The integumentary system consists of hair, skin and nails while the skeletal system consists of the bones in our body that provide support for posture and movement. The muscular system aids in movement as well as other process such as digestion. The urinary system acts as a plumbing system for the human body and filters out toxins and wastes from the blood.
The digestive system helps break down food and release nutrients into the bloodstream and the excretory system. The digestive process consists of important processes including ingestion, digestion, absorption and excretion. Nutrition affects physiological processes and crucial functions in the body. Nutrients are important for a number of important functions including cellular structure and healthy cellular function.
Inadequate levels of nutrition can impact our wellbeing in different ways and lead to several adverse health consequences. Consumption of proper nutrients helps optimise wellbeing, improve vitality and enhance protection from disease.
Nutrition and physiology
As early as 400 B.C, Hippocrates said that food should be our medicine. Understanding the different physiological needs of our body helps us appreciate why food is vital to our health and wellbeing. The nutritional needs of people (starting from your family and loved ones) are important not only for general welfare but also for economics. Preventing disease involves far less expenditure compared to treating it. Food has been a basic part of our existence and survival, and our bodies are kept alive by complex physiological processes that help perform multiple functions. Meeting our daily nutritional requirements helps replenish important molecules including carbohydrates, fats and proteins.
Similarly, vitamins and minerals are important for enzyme and metabolism. This module will provide an overview of different organ systems in the body, and will help the student understand the terms and jargon used in subsequent modules.
2.2 The Skeletal System
The skeletal system comprises all the bones and joints in the body. Each bone is a complex structure made of protein fibres, minerals and thousands of cells. The skeletal system provides support and protection to the organs and provides important points where muscles can attach to bones to enable movement.
Bone marrow is the soft, jelly-like substance inside bones where red blood cells are produced. The skeleton grows during childhood and reaches its full size when the individual reaches adulthood. The skeletal system houses about 206 bones and consists of various parts including the skull, ribcage, pelvic and pectoral girdle, vertebral column, upper and lower limbs, auditory ossicles (small bones located in a small cavity in the ear) and hyoid (a small bone shaped like a 'U' located just below the mandible (lower jaw bone).
The vertebrae consist of neck (cervical), chest (thoracic), lower back (lumbar), tailbone (coccyx) and sacrum (this is a wedge-shaped vertebrae located in the inferior end of the spine). The pectoral girdle helps connect the upper arm bones to the main skeleton. Similarly, each finger has three bones known as phalanges except the thumb that has two phalanges. The patella is the knee cap while the femur is the thigh bone and the longest bone in the body.
Bones are made up of water, collagen, calcium phosphate and calcium carbonate. The living cells of the bones exist on the edges of the bone and help in growth and development, recovery from wear and tear and bone resorption that takes place to release minerals into blood. Collagen fibres are used to anchor muscles and tendons to the bone. Small cells known as osteocytes help maintain integrity and strength of the bone. An articulation is a gap between bones or between cartilage and bone. The gap is usually filled with synovial fluid, which works to lubricate the joint.
Physiology of the skeletal system
The skeletal system provides support to the body and protects organs against injury. The bones improve flexibility and support to muscles that help move the limbs. Bones grow larger and stronger in the areas where they are attached to muscles. Density and structure of bones may be significantly impacted by nutrients. Haematopoiesis is the process by which the soft bone marrow produces red blood cells.
In addition, the skeletal system also stores reserves of calcium and releases calcium ions into the blood whenever required. In addition, bones also release osteocalcin - a substance that helps regulate fat deposition and blood sugar. Bone marrow also stores iron that is used in the formation of red blood cells.
2.3 Muscular System
There are about 700 muscles in the body that make up about half the weight of the body. Each muscle is made up of blood vessels, muscle tissue, nerves and tendons. Muscle tissue is also found inside the heart, blood vessels and digestive organs. Muscles can be of three types: visceral, cardiac and skeletal muscles. Visceral muscles are found in blood vessels, intestines and stomach. Cardiac muscles are found only in the heart and they are responsible for pumping blood around the body. The cardiac muscle cells are tightly bound by intercalated discs (special junctions) that help in the transmission of electric signals.
Skeletal muscles help in movement and they can be controlled consciously. Even small movements such as speaking or writing involve the use of skeletal muscles. Skeletal muscles always connect to bones at least at a single point. Muscles are attached to bones through tendons which consist of dense, connective tissue linked to bones by means of collagen fibres. Muscles always work in pairs and the fleshy, middle part of the muscle is where the actual contractions take place.
There are three main types of blood vessels: arteries, veins and capillaries.
Arteries are responsible for transporting oxygenated blood to all tissues of the body and blood rushes through arteries with great force. Important arteries contain a high percentage of elastic tissue in order to accommodate blood flow and the walls of smaller arteries expand and contract to adjust to blood flow. Arterioles are smaller arteries located at a greater distance from the heart and hence accommodate much reduced blood flow and pressure.
Capillaries are the smallest of blood vessels and carry nutrients to cells and carry away cellular waste products. Smooth muscles known as sphincters help regulate the amount of blood entering a capillary. Veins carry away deoxygenated blood from the tissues back to the heart and have much thinner walls with less muscle compared to arteries and capillaries. Most of the pressure from the heart is absorbed by capillaries and arteries.
Veins located in the stomach and intestines perform a unique function. They carry blood to the liver through the hepatic portal vein. The blood from digestive organs is rich with nutrients and chemicals and the liver then removes metabolic toxins and wastes, stores sugar, and processes other products of digestion. The blood from the liver is then returned to the heart through the vena cava.
Red blood cells
Red blood cells are made of haemoglobin that contains proteins and iron. Since red blood cells do not have a nucleus, they are unable to repair themselves due to the absence of DNA.
White blood cells
White blood cells are responsible for ingesting pathogens and dead cells, and help fight infection.
Plasma
Plasma is the liquid portion of blood that makes up about 55% of blood volume. Roughly 90% of plasma is made up of water and the remaining 10% of made up of proteins and dissolved substances. Dissolved substances can include oxygen, carbon dioxide, nutrients, glucose, cellulites and metabolic waste products. The cardiovascular system performs three important functions that include: transportation of substances, improved immunity from pathogens and regulating the process of homeostasis.
Homeostasis
Homeostasis is the process of maintaining a regular and stable internal environment in the body. Several organ systems work together in the process of homeostasis which also involves stabilising the hormone levels in the body. Homeostasis comprises three main types of homeostatic processes, including osmoregulation (control of salt and water levels), thermoregulation and chemical regulation. Chemical regulation occurs after every meal when glucose levels rise in the body and the pancreas releases insulin for sugar control. Blood vessels also help maintain pH levels with the help bicarbonate ions.
Blood pressure
The cardiovascular system is also responsible for control of blood pressure. The strength and rate of heart contractions are controlled by nerve signals and the release of certain hormones in the brain. Greater volume of blood and thicker blood (with higher viscosity) resulting from clotting can also impact blood pressure. Platelets form spiny balls at the site of wounds or damaged tissue and release a protein called fibrin that helps the blood vessel repair itself. In biological terms, the clotting of blood is known as haemostasis.
Fact
Red blood cells make up about 45% of blood and are produced inside bone marrow at the rate of 2 million cells per second. At any given time, we have about 30 trillion blood cells in our body
Source: www.bbc.co.uk
2.5 The Endocrine System
All the glands and hormones released by glands make up the endocrine system. The endocrine system is responsible for a number of crucial functions in the body including cellular metabolism, homeostasis, regulation of sugar and mineral levels, reproduction and sexual functions, and digestion as well as heart rate. The pituitary gland is located in the hypothalamus in the brain and is responsible for many different functions in the nervous system. Some important hormones include adrenaline, cortisol, growth-stimulating and growth-inhibiting hormones, endorphins and so on.
2.6 The Nervous System
The nervous system consists of the brain, spinal cord and nerves, and the system is responsible for evaluating information and making decisions. Nerve cells or neurons communicate using electric signals and appear different from other cells due to the small branch-like structures called dendrites that pick up stimuli. Neuroglia cells are helper cells that surround each neuron and help them perform their functions. Neurons in general are highly specialised cells that almost never reproduce and they are crucial for the optimal functioning of the nervous system. The brain weighs roughly about three pounds and is a soft, wrinkled organ located inside the cranial cavity. The brain and spinal cord together form the central nervous system where information is processed. The brain controls multiple functions of the body including respiration, blood pressure, heart rate and movement.
The space between the brain and the skull and the spinal cord and vertebrae is filled with 'cerebrospinal fluid' called CSF for short. The CSF helps maintain chemical homeostasis and contains oxygen, nutrients, albumin and ions that help preserve the osmotic and chemical balance within neurons. Electrical signals are sent from one neuron to another through gaps called electrical and chemical synapses. Calcium ions play a crucial role in this process.
The axon of nerve cells (the axon refers to the long, thread-like structures at the end of a nerve cell) are covered in a protective substance called myelin which helps speed up the transmission of nerve signals in the body. Myelin is made up of thick coatings of lipids. The nervous system is responsible for movement, sensory messages (taste, touch, sight, auditory impulses and olfactory impulses) and speech and so on.
2.7 The Respiratory System
The basic function of the respiratory system is to enable the exchange of oxygen (into the body) and carbon dioxide (out of the body). Important parts of the respiratory system include the nose, trachea, lungs, larynx, pharynx, bronchi and diaphragm. The mucus and hair lining in the nose warms, moisturises and filters the air that we breathe in to remove bacteria.
An elastic flap of cartilage known as the epiglottis covers the trachea when food is eaten and covers the oesophagus (food pipe) when air is breathed in. The air then enters the trachea (wind pipe) that controls air entering and exiting the lungs. The cells lining the trachea (called epithelial cells) trap dust and other contaminants from the air by secreting sticky mucus. The lungs are large spongy structures that contain capillaries as well as millions of air sacs known as alveoli. There are also several intercostal muscles that help contract and expand the lungs during the process of respiration.
The main physiological functions of the respiratory system involve exchange of gases and ventilation. Oxygen from the air is inhaled and released into the body while waste carbon dioxide is removed from the body and released into the air. Haemoglobin is a red pigment found in blood that carries oxygen and also carries back a small amount of carbon dioxide. The main carriers of waste carbon dioxide are bicarbonate ions. An enzyme known as carbonic anhydrase helps carbon dioxide react with water to produce carbonic acid.
2.7 The Urinary System
The urinary system consists of kidneys, urethra, ureters and urinary bladders, and the system is primarily responsible for the removal of wastes and toxins from the blood. The urinary system acts like a plumbing system that drains urine from blood, stores it in the bladder
and releases it from the body through the urethra.
In addition to filtering out toxins and wastes from blood, the urinary system also helps maintain homeostasis of ions, water, pH, calcium, blood pressure as well as red blood cells. The kidneys are bean-shaped organs that filter out wastes, chemicals and excessive ions and they are surrounded by adipose tissue (made of fats) to protect them from shock and damage. The urinary bladder is a hollow, sac-like organ that stores urine before it is released through the urethra and it can hold between 600-800 ml of urine.
The sphincter muscles help control the release of urine through the urethra and they allow urine to pass through when the bladder reaches a certain level of distension. Kidneys are responsible for regulating the secretion of ions including iron, calcium, phosphate, magnesium, potassium, sodium and chloride ions. When the levels of these ions are less than normal, the kidneys can also conserve the ions in blood during the process of filtration. Kidneys also play an important part in maintaining blood pressure by reducing or increasing the volume of water in the blood. They also produce the active form of vitamin D known as calcitriol. Calcitriol helps increase the percentage of calcium in the blood. Proper nutrition and intake of adequate water can help the urinary system function at its best.
Fact
Kidneys filter about 180 litres of blood on a daily basis and each kidney is around 10-12 cm long. Statistics indicate one in 8 people in the UK develop chronic kidney disease and roughly 64,000 people are currently being treated for kidney problems in the UK
Source: www.kidneycareuk.org
2.8 The Integumentary System
The integumentary system consists of skin, nails and hair and exocrine organs. The system is responsible for producing sweat, wax, and oil to cool, protect and hydrate the surface of the skin. The skin is made up of the epidermis which in turn is made up of a large majority of cells known as keratinocytes. Roughly 90% of the epidermis is made of keratinocytes and another 8% is made of melanocytes. These cells produce the pigment melanin that helps protect the skin from UV radiation, and contain the protein keratin. Dead keratinocytes are shed from the skin regularly.
The dermis is thicker and denser than the epidermis and is made of elastic collagen fibres and connective tissue. Deeper than the dermis is the hypodermis that is made up of adipose tissue that stores energy in the form of triglycerides. Hair is made up of dead keratinocytes and each hair consists of the follicle, root and shaft. The hair shaft and root are made up of three distinct layers called cuticle, medulla and cortex. The medulla contains high amounts of keratin pigments. Nails are made up of hardened keratinocytes and the root of the nail is found under the skin. The stem cells present in nails undergo reproduction to form keratinocytes which in turn manufacture the keratin protein.
Sweat glands are found in the dermis layer of the skin and are known as sudoriferous glands and they secrete a mixture of sodium chloride and water. Apocrine sweat glands are activated upon puberty. They produce a viscous liquid that is broken down by bacteria which live on the skin. The skin also helps trap sunlight and specialised cells help convert it into vitamin D. In addition, skin is a thermal regulator and helps maintain optimal temperatures within the body. Sweat helps excrete metabolic wastes including lactic acid, uric acid, urea and ammonia. Consuming the right nutrition can help maintain healthy skin, hair and nails. What we eat can affect factors like body odour and oiliness of skin, or even acne.
Activity
Estimated time: 5 minutes
Why do you think that some of us have healthy, glowing skin and hair while others suffer fromproblems?
Could it be a mix of genetic factors as well as quality of nutrition that we consume?
2.9 The Digestive System
The digestive system consists of a set of organs that help release nutrients from food by breaking food down into digestible forms. Organs constituting the digestive system consist of the teeth, salivary glands, oesophagus (food pipe), stomach, liver, gall bladder, and pancreas as well as small and large intestine. Four major processes comprise the process of digestion and this includes: ingestion, digestion, absorption and excretion.
Digestion can be mechanical as well as chemical and each organ in the digestive system is responsible for performing a unique function in the breakdown of food. The teeth chew food into smaller particles which are then coated with saliva in order to be sent down to the stomach through the oesophagus. The food moves down the oesophagus (which is roughly 10 inches in length) through a process of muscle movement called peristalsis. The stomach is roughly the size of two βists placed next to each other and it churns the food into 'chyme'. Chyme consists of partly digested food mixed with hydrochloric acid, which kills bacteria.
Food digestion is completed in the small intestine and 90% of the nutrients are absorbed into the bloodstream. Different enzymes act on proteins, carbohydrates and fats in order to chemically break them down into easily digestible molecules.
For example
Pancreatic juice, contains complex enzymes that are capable of digesting lipids, carbohydrates, proteins and nucleic acids. The food molecules are absorbed by the intestine wall through the processes of passive and active diffusion. Carrier molecules known as micelles help carry fat molecules into the bloodstream.
The large intestine (also called the colon) absorbs excess water from the food and the remaining, undigested food is excreted in the form of faeces. There are also symbiotic bacteria present in the large intestine that help break down the remaining nutrients. The colon also helps with absorption of vitamin B and K before faeces leaves the body through the anal cavity. The digestive system is where nutrients from food get converted into their digestive forms and are released into the bloodstream, from where they are distributed to all cells.
MODULE SUMMARY
Our body is made up of different organ systems which are made up of tissues which in turn are made up of cells. Nutrition impacts our bodies at the cellular level and can result in negative health consequences leading to sickness and even death. The important organ systems consist of digestive system, nervous system, endocrine system, skeletal and muscular system, integumentary system, urinary system and excretory system. Each system performs a set of crucial functions which helps optimise health and wellbeing.
Food is broken down by the digestive system and nutrients are released into the bloodstream. Macromolecules are broken down into micromolecules due to enzymatic action. The energy is released by the respiratory system which also aids in the exchange of gases. The respiratory system helps in the intake of oxygen and releases carbon dioxide out of the body. The cardiovascular system consists of the heart, veins and arteries and it helps transport nutrients as well as other substances to different cells in the body. Kidneys, which are a part of the urinary system help filter out wastes and maintain homeostasis.
.svg)
