SNC2D Grade 10 Academic Science Biology Cells and Tissues

Thanks, Tony!

Biology: Chapter 3 Notes

 

Chapter 3.1—Cells and Tissues

Cell Specialization

  • in a single celled organism, one cell has to be able to do everything that is needed for the organism to survive (find food, break it down, release the energy etc.)
  • in multicellular organisms, survival tasks are handled by groups of specialized cells
  • there are 3 factors that influence cell specialization:
    • the contents of the cell’s cytoplasm
      • mitosis ensures daughter cells receive identical sets of chromosomes, but cytokinesis doesn’t ensure that the contents of the cytoplasm is divided evenly (ex.:  one daughter cell may have more storage vacuoles than another)
      • the contents of the cytoplasm in the daughter cells allows some cells to be specialized for certain tasks
    • environmental conditions (e.g. temperature)
      • environmental conditions such as temperature or presence/absence of certain nutrients for example
      • differences in environmental conditions explains why cells with identical genes will develop differently
      • in Siamese cats, cells that develop at cool temperatures (feet, tail, ear, nose) produce darker hairs than cells who’s environmental conditions did not include being in a cool temperature
    • the influence of neighbouring cells
      • one of the biggest influences on what a cell will become
      • when cells are close to one another, the substances produced by one cell can sometimes diffuse through a neighbouring cell’s membrane
      • these diffused substances can change how the information in the DNA of the second cell gets expressed (changes how genes in receiving cell of diffused materials get expressed; therefore changing the function of cell)
  • chemical contaminants in the environment can trigger abnormal development (exposure to heavily metals for example)
  • as a cell matures, more and more genes get turned off or on by the effects of other cells or environmental conditions
    • one combination of active and inactive genes will produce a specific type of cell (specialized)
    • eventually, cells have had so many of their genes turned off that they eventually stop dividing (leaves the cell cycle)
  • groups of similarly specialized cells form tissues—had experienced similar factors of differentiation

 

Types of Tissues

  • epithelial tissue lines the surface of the body, both as a body covering and between internal organs; cells have strong connections between adjoining cell membranes, so they can form barriers
    • skin epithelia tissue 
      • made of thin, flat cells that form sheets
      • act as a semi-permeable barrier between the inside and outside of body
    • columnar epithelia tissue
      • columns of cells that line the small intestine, stomach and glands’
      • may secrete mucus, may have cilia, and may also absorb nutrients
  • muscle tissue are able to change their shape by shortening or lengthening their cell
    • skeletal muscle tissue
      • made of cells that line up in the same direction (tissue looks striated)
      • attaches to bone making it possible for body to move
      • found in limbs (arm) and places where body needs support (abdomen)
    • smooth muscle tissue 
      • made of cells that are tapered at both ends (don’t have striated pattern)
      • found in blood vessels and walls of internal organs (like esophagus and stomach)
    • cardiac muscle tissue 
      • made of cells whose nuclei sometimes appear to be in between cells
      • are branched and unevenly striated
      • contracts as a unit
      • found only in heart
  • nervous tissue is made up of cells called neurons which have finger-like projections to receive and transfer signals
      • coordinates body movement
      • have various tasks: relay signals from brain/spinal cord to muscles and glands; detect information from environment (take hand away from burning stove)
  • connective tissue strengthens, supports, protects, binds or connects cells and tissues; consists of cells in an extracellular matrix that can range from a liquid (in blood) to mineral deposits (bone)
    • bone tissue
      • made of cells surrounded by calcium-hardened tissue through which blood vessels run
      • needed for movement, support, and protection
    • fat (adipose) tissue
      • made of large, tightly packed cells
      • found under the skin and around organs
      • needed for energy storage, padding and insulation
    • blood 
      • includes red and white blood cells, platelets (stored within a straw-coloured matrix called plasma)
      • transports nutrients and oxygen
      • clots when the skin is cut
      • attacks invaders such as bacteria and viruses

 

Stem Cells

  • stem cells produce more cells for animal to become larger
  • a stem cell is an unspecialized cell that can produce various specialized cells
    • similar to the meristematic cells in plants
  • embryonic stem cells are unspecialized cells that can become ANY cell in the organism’s body
  • some animals (starfish and salamanders) can regenerate some body parts, but mammals (humans) can replace only small amounts of tissue (such as for bone and skin repair)
    • human organs are formed in the embryo; the human body can’t produce new organs
  • human embryos first have totipotent stem cells (can become ANY cell), and later on in development, the embryo has pluripotent stem cells instead (less versatile than totipotent cells, but more versatile than adult stem cells; creates many cells, but not all cells)
  • after birth (and at the very last stages of embryo development), humans have only adult stem cells—they can produce only specific kinds of cells (for example, only bone stem cells can produce new bone cells)
  • stem cells have many medical uses—bone marrow can be transplanted from a healthy person to a person who has undergone radiation to replace the destroyed bone marrow, in order for the person to produce more R.B.C.
  • scientists obtain embryonic stem cells from fertilized eggs from in vitro that aren’t used; however this destroys the embryo
    • some see this as taking a human life
  • scientists have discovered that some adult stem cells (ex.: skin) can be induced to become pluripotent cells
    • however, most cells are induced by viruses, which could potentially damage the stem cells’ DNA

 

Chapter 3.2—Organs and Systems

Medical Imaging Technology

  • medical imaging technology are techniques used to form an image of a body’s internal cells, tissues and organs
  • allows doctors to diagnose patients
  • there are many factors which influence a physician’s decision on which technology to use: cost and impact on patient (pain, sickness, radiation etc.) for example
  • X Ray
    • produced by transmitting a wavelength of electromagnetic radiation through the body to expose photographic film on the other side
    • x rays go through soft tissue—therefore x rays are best used for hard tissue (like bone)
  • CT/CAT Scan (computerized axial tomography)
    • produced by taking X rays of very thin “slices” of a body part
    • these slices are reconstructed by a computer into a 3D image
  • Ultrasound
    • produced by directing high frequency sound waves at a part of the body, usually from a microphone attached to a computer
    • shows real-time movement of body parts like the heart; useful for watching organ function
  • MRI Scan (magnetic resonance imaging)
    • produced using radio signals in a magnetic field to create images of body parts
  • endoscopy
    • a tiny camera and a light attached to a flexible tube is inserted into the body; provides options for diagnosis as well as treatment
    • ulcers are most commonly diagnosed with this technology—an ulcer is a hole in the protective mucous lining of the stomach/intestine, thus allowing gastric juices to start digesting body tissue

 

The Body’s Organization: A Hierarchy

  1. organelle—specialized to perform a task within a cell
  2. cell—specialized to perform a task
  3. tissue—a collection of cells performing the same task
  4. organs—a collection of tissues to perform a more complex task
  5. systems—a collection of organs to perform a more complex task

 

Human Organ Systems

  • there are 11 organ systems in the human body, and they are:
    • circulatory system
      • transports blood, nutrients, gases and wastes
    • digestive system
      • takes in food and breaks it down
      • absorbs nutrients from food
      • removes solid waste from the body
    • respiratory system
      • controls breathing
      • exchanges gases in lungs
    • excretory system
      • removes liquid wastes from the body
    • immune system
      • defends the body against infections
    • muscular system
      • works with the bones to move parts of the body
    • endocrine system
      • manufactures and releases hormones that act (along with the nervous system), to keep various body systems in balance
    • reproductive system
      • allows individuals to produce offspring
    • integumentary system
      • includes the hair, skin, and nails
      • creates a waterproof barrier around the body
    • nervous system
      • detects changes in the environment and signals these changes to the body which then responds
    • skeletal system
      • supports, protects, and works with muscles to move parts of the body

 

Digestive System

  • mechanically and chemically breaks down food to produce nutrient molecules that the body`s cells can absorb and use
  • order of digestive system:
    • mouth (containing salivary glands and tongue)
      • digestion begins (teeth do mechanical digestion; salvia, an enzyme begins chemical digestion)
    • pharynx
    • esophagus
      • muscular walls contract and relax to push food down chunks down to stomach
    • stomach (contains a lower esophageal sphincter and a pyloric sphincter—opening and closing of stomach)
      • food chunks arrive in stomach
      • gastric juices (secreted by columnar epithelial tissue) surround food—hydrochloric acid and the enzyme pepsin (pepsin must be in an acidic environment in order to break down the proteins)
      • stomach lining secrets mucus, protecting the stomach from being broken down by the gastric juices
      • nerves in the stomach wall sense the presence of food, in order to signal the stomach`s muscle tissue to mix the contents, continuing mechanical digestion on top of the chemical digestion from juices
      • the partially digested food becomes a liquid
    • small intestine (liver, gall bladder and pancreas)
      • when food is fully mixed, a round muscle at the bottom of the stomach (sphincter) relaxes, allowing some of the contents of the stomach to be released into small intestine
      • first metre of small intestine is called the duodenum (where most of digestion takes place)
      • there are small tubes (ducts) that connect to the pancreas, liver, and gall bladder—these organs release more digestive enzymes into the duodenum which completes the chemical breakdown of food
      • when the digest food moves into the remaining length of small intestine, it`s ready to be absorbed into the body
        • the small intestine is covered with many interior folds (called villis and microvilliis)
      • absorbs water and nutrients into the blood
    • large intestine (colon, rectum and anus)
      • has a larger diameter but is shorter in length than small intestine
      • main function is to absorb water, vitamins, and various salts from the digested food and to eliminate undigested food (cell walls of plants) through the anus as feces
      • also contains bacteria to finish the process of breaking down food and to also produce essential nutrients (vitamin K)
      • allows waste to become solid

 

Excretory System

  • digestive system is responsible for eliminating solid waste; excretory system is responsible for liquid waste
  • water and other materials are absorbed through the walls of the large intestine and move into blood vessels
  • as the blood passes through the kidneys, it is filtered and the wastes are removed
    • as blood is filtered, urine (containing water and unneeded salts is formed)
  • urine is then stored in the bladder; when it is full, the urine is flushed from the body

 

Circulatory System

  • picks up and transports nutrients and oxygen to cells and carries wastes to the organs responsible for eliminating them from the body
  • arteries carry blood from the heart to the rest of the body; veins carry blood from the body back to the heart
  • the blood interacts with every other organ system
  • the human heart has 4 chambers: left and right atrium; left and right ventricle
  • when the heart contracts, it produces pressure on the blood in the system
    • this pressure pushes blood through the body
    • flexible flaps of tissue, called valves, are found throughout the circulatory system, including the heart and veins
      • they open when blood is pushed through them, and then closed to prevent blood from flowing backward
  • process of blood going through the heart
    • deoxygenated blood comes to the heart from body
    • it goes through the right atrium and then down to the right ventricle
    • the blood in right ventricle gets pumped through the pulmonary artery to the lungs
    • when at the lungs the blood eliminates the carbon dioxide and picks up the oxygen
    • the oxygenated goes back to the heart, through the left atrium and down the left ventricle
    • from the left ventricle, blood is pumped out through the aorta (a huge artery) to the rest of the body
      • some of this oxygenated blood goes to the heart itself
  • all multicellular organisms have a way of getting oxygen to their cells
    • some circulatory systems (insects) are said to be open—they have one major vessel that empties oxygenated blood into body parts (cells are bathed with blood); movements of body muscles take the blood back to be collected by the single vessel
      • mammals have the opposite—they have a closed circulatory system (blood steins in vessels)
    • fish have two chambered hearts, and amphibians have 3 (frogs)
      • the frog has 2 atriums but 1 ventricle; this means there is some mixing of oxygenated and deoxygenated blood (so some of blood pumped back to body is deoxygenated—however oxygen also diffuses through moist skin to make up for the mixing of blood)
  • capillaries connect arteries and veins
    • are very small (only one epithelial cell thick)
    • areas where capillaries are close to one another are called capillary beds
    • capillaries bring blood into close contact with the tissues in organs throughout the body
      • ex: capillaries bring blood into contact with the small intestine’s villi and microvilli in order to pick up nutrients from digested food; also bring blood into close contact with alveoli in lungs for gas exchange
      • in every tissue of the body, capillaries deliver blood rich in oxygen and nutrients; at the same time, blood in capillaries pick up wastes from cells and transports them to the kidneys and lungs
  • the delivery of blood is essential for the proper functioning of all other systems in the human body
    • heart disease can be caused by hypertension and arteriosclerosis (thickening of the artery walls which narrows the passageway for blood)
    • hypertension and arteriosclerosis can cause blood clots
      • if a blood clot breaks free it can reach the brain and block a vessel (resulting in stroke—stops blood flow to brain, starving cells of oxygen)
      • angioplasty uses a balloon or laser to try and open up clogged arteries

 

Respiratory System

  • responsible for the body’s gas exchange—brings oxygen in and lets carbon dioxide out
  • the respiratory system is connected to the circulatory system—one system couldn’t do without the other
  • when you breathe, muscle contractions cause your rib cage to move up and out and your diaphragm moves down
  • order of the respiratory system:
    • air is pulled into your body through nose/mouth
      • they pass by epithelial cells that have cilia (hair like projections) which secrete mucus—mucus and cilia keep foreign particles (dust, bacteria etc.) out of the body
    • naval cavity (filters, warms and moistens air)
    • pharynx
    • epiglottis
      • prevents food from entering the trachea
    • larynx (contains vocal cords)
    • trachea
      • carries the air to the bronchi
    • bronchus (plural bronchi)
      • carries air to the lung
    • lung (bronchiole and alveoli)
      • bronchiole—leads air to alveolis
      • alveoli—a thin layer of epithelial tissue around alveoli keeps inhaled bacteria and viruses inside outside the bloodstream, while allowing gases to cross (oxygen in and carbon dioxide out of blood)
    • diaphragm (located below lung)
  • red blood cells contain a protein called haemoglobin (attached to oxygen molecules)
    • when deoxygenated red blood cells pass by the alveoli, the haemoglobin they contain causes them to pick up oxygen
  • when you exhale (chest muscles and diaphragm relax), the carbon dioxide is exhaled as it’s carried out of alveoli and out the body
  • the human body constantly monitors carbon dioxide levels—if they’re too high, breathing rate increases to the waste products can be eliminated quicker
  • smoking can cause many respiratory system problems
    • smoking damages the cilia—prevents them from sweeping foreign particles out
    • contains 40 known carcinogens (cancer causes)
    • causes high levels of carbon monoxide to build up in body (bad for body)
    • tar accumulates in lungs
  • not all animals have lungs: some like fish have different ways for gas exchange to occur (gills)

 

Anatomical Arrangements

  • the efficiency in our organs and organ systems and their ability to interact is due to their placement in the human body
    • example: close contact between capillaries and villi; close contact between capillary and alveoli
    • example: biceps contract, pulls bone in forearm up

 

Handouts and Slideshow Notes

CELL SPECIALIZATION

  • when new cells are produced through mitosis, different factors can cause them to specialize
    • change in shape and structure of the cell helps it perform different functions
  • during cell division, a stem cell can divide into more stem cells or divide to become a specialized cell

 

  • cellular respiration is the process of releasing stored energy by breaking down glucose; occurs in the mitochondria of the cell
    • glucose + oxygen  carbon dioxide + water (+ energy)

 

  • cells need oxygen, glucose, water, get rid of waste, and minerals (potassium, calcium etc.)
  • worm digestive system: mouth, esophagus, crop, gizzard, intestine
    • clitellum located near anterior (not posterior side)

 

Respiratory System

  • unicellular organisms diffuse gas
  • skin respiration is when gas diffuses through moist skin (worms(
  • fish have gills
  • grasshoppers have a tracheal respiratory
  • frogs use lungs and skin

 

Circulatory System

  • unicellular organisms have their nutrients diffused through the cellular membrane
  • open circulation is when blood doesn’t travel within vessels (grasshopper); has only an aorta
  • closed circulation is when the blood stays within the vessels of the body; blood flows in one direction
  • fish have 2 chambered hearts
  • frogs have 3 chambered hearts—they have 2 atriums 1 ventricle (oxygen and deoxygenated blood mix)
  • mammals have 4 chambered hearts

 

Digestive System

  • gill feeders filter their food from the water using teeth, gills etc.
  • fluid feeders thrive off of fluid (mosquitoes and blood)
  • chunk feeders have a tube arrangement allowing for transport of food to be brought to a specific part of the inside of the organism
    • open tube is mouth  anus; closed tube means food enters and exits from same location
  • unicellular organisms use intracellular organisms—food enters cell before digestion

 

Stem Cells

  • adult stem cells are hard to obtain—they can’t be stored for long in lab setting, and can only turn into a few cells