Human Anatomy

Lecture 2

Study of Cells

  • Cell shapes and sizes
  • Shapes – organs and tissues are often described according to the shapes of their cells
  • ______– thin, flat, scaly
  • Cuboidal- roughly equal in length, width, and height
  • ______- distinctly taller than they are wide
  • Polygonal- having irregularly angular shapes with four or more sides
  • ______- having multiple pointed processes, which give the cells a somewhat starlike shape
  • Spheroid to ovoid- round to oval in shape
  • Discoid- disc-shaped
  • ______- spindle-shaped; elongated with a thick middle and tapered ends
  • Fibrous- long, slender, and threadlike
  • Sizes
  • A micrometer is one-millionth of a meter
  • Most human cells are about 10 to 15 micrometers wide
  • Cell size is limited:
  • If a cell were too large, molecules could not ______from place to place fast enough to support metabolism
  • Time required for diffusion is proportional to the ______of distance, so if cell size is doubled, the travel time for molecules within the cell is quadrupled
  • Cells size is limited by the relationship between its volume and surface area
  • The surface area is proportional to the square of its diameter, while the volume is proportional to the ______of its diameter, so volume increases much faster than surface area as diameter increases.
  • At some point a cell becomes so large that there isn’t enough surface area to absorb nutrients and to get rid of wastes
  • The major components of a cell
  • Plasma membrane – forms the surface boundary of the cell
  • Cytoplasm – material between the cell membrane and the nucleus
  • Cytoskeleton – supportive framework of protein filaments and tubules
  • Organelles – diverse structures that perform various ______
  • Inclusions- include stored cell products such as lipids and pigments and foreign bodies such as dust and bacteria
  • Cytosol- a clear gel or fluid inside the cell
  • Nucleoplasm – material within the ______

Cell Surface

  • Plasma membrane – essentially a two-layered lipid film with proteins embedded in it
  • Membrane Lipids
  • Phospholipids make up 75% of the membrane lipid molecules
  • Two fatty acid tails are ______, while the phosphate-containing head is hydrophilic.
  • The tails orient away from the water, while the heads orient towards the intracellular fluid and extracellular fluid
  • The molecules drift from place to place, keeping the membrane ______
  • Fat soluble substances pass in and out of the cell through this phospholipid bilayer
  • Membrane Proteins
  • Proteins may pass all the way through the plasma membrane (integral proteins), or they may simply adhere to the face of the membrane (peripheral proteins)
  • Roles:
  • ______– some hormones and neurotransmitters bind to cells at these proteins to trigger physiological changes inside the cell
  • Enzymes – after chemical messages are received, some membrane proteins break down those messengers
  • Channel proteins – water and solutes may pass through tunnels made of proteins to enter or leave the cell membrane
  • Cell ______markers – some proteins function as genetic identification tags to allow the body to determine if cells belong to the body or are foreign
  • Cell adhesion molecules – some proteins allow cells to stick to each other
  • ______– some proteins actively bind to a substance on one side of the membrane and then release it on the other side
  • Membrane Transport – One of the most important functions of the plasma membrane is to control the passage of materials into and out of the cell
  • ______– a process in which a physical pressure forces material through a membrane
  • Example: blood pressure forces fluid to seep through the walls of the blood capillaries into the tissue fluid
  • This allows water, salts, and nutrients to be passed from the blood to the cells surrounding a blood vessel
  • Simple diffusion- the net movement of particles from a ______concentration to a lesser concentration
  • Molecules diffuse through a membrane if the membrane has large enough pores
  • Selectively permeable membranes allow some molecules to pass through, but not all of them
  • Osmosis – the diffusion of water through a selectively permeable membrane, from the side where water is more concentrated to where water is less concentrated
  • Facilitated ______– movement of a solute through a membrane, down its concentration gradient, with the aid of a carrier
  • The carrier binds to the particle on one side, where the solute is more concentrated, and releases it on the other side, where it is less concentrated
  • Active ______– carrier mediated transport of a solute through a membrane up its concentration gradient, with the expenditure of adenosine triphosphate
  • ATP is essential to the process because moving particles up a concentration gradient requires an input of energy
  • Vesicular transport – movement of larger particles or droplets of fluid through the membrane in bubble-like vesicles
  • Movement of material into the cell is ______
  • Movement of material out of the cell is exocytosis
  • Glycocalyx – A layer of carbohydrates on the glycoproteins and glycolipids of the plasma membrane forms a fuzzy, sugary coating
  • The coating cushions the plasma membrane and protects it from ______
  • The coating functions in cell identity (distinguishing cells from diseased cells or invading organisms)
  • The coating contains cell-adhesion molecules that help bind tissues together
  • Microvilli, Cilia, and Flagella
  • Microvilli- extensions of the plasma membrane that increase surface area
  • Cilia- ______processes that extend from cells
  • Motile cilia beat in waves that move materials (such as mucus or egg cells) along the outside surface of the cell
  • Non-motile cilia are not well-understood, but some are sensory
  • Flagella- long whiplike tails for movement of sperm cells
  • Intercellular Junctions – arrangements of proteins that link cells together and attach them to extracellular material
  • Tight Junctions- A zipperlike junction between epithelial cells that limits the passage of substances between them
  • ______-A patchlike intercellular junction that mechanically links two cells together
  • Gap ______- A junction between two cells consisting of a pore surrounded by a ring of proteins in the plasma membrane in each cell
  • The pore allows solutes to diffuse from the cytoplasm of one cell to the next, which makes communication between cells possible

Cytoplasm

  • The Cytoskeleton – system of filaments and tubules that provide physical support, allow cellular movement, and control routing of molecules and organelles to their destinations within the cell
  • Organelles
  • The nucleus – round or oval shaped structure near the center of the cell containing DNA
  • ______Reticulum – An extensive system of interconnected tubules or channels enclosed in a membrane
  • Rough endoplasmic reticulum – contains ribosomes and synthesizes proteins for export from the cell
  • Smooth endoplasmic reticulum – involved in detoxification, steroid synthesis, and storage of calcium ions (in muscle cells)
  • Ribosomes – Granules composed of ribosomal RNA and enzymes that read sequences of messenger RNA to assemble sequences of amino acids to make proteins
  • ______Complex – Organelle that modifies and packages newly synthesized proteins and synthesizes carbohydrates
  • Lysosomes – Organelles that contain enzymes that are used to digest foreign matter, pathogens, and expired organelles
  • Peroxisomes – Organelles containing enzymes that detoxify drugs and break down fatty acids, producing hydrogen peroxide in the process
  • ______– Organelles specialized to synthesize ATP (for energy)
  • Centrioles- Organelles composed of a short cylinders of microtubules, that are the origin of the mitotic spindles (used in cell division)
  • Inclusions- Any visible object in the cytoplasm of a cell other than an organelle or cytoskeletal element, such as a dust particle, lipid droplet, or pigment

Life Cycle of Cells

  • Cell Cycle – the life cycle of a cell, extending from the time that a cell is produced by cell division until it produces daughter cells by cell ______.
  • Cell Division
  • Meiosis – the production of egg and sperm cells (haploid cells)
  • Mitosis – produces identical cells for growth or replacement of damaged cells
  • Several phases are involved in mitosis
  • Interphase actually precedes replication activities, and it’s the phase in which most cells remain for long periods of time. It’s important for mitosis because it’s a phase in which the ______is replicated
  • Prophase is a phase in which the DNA chromosomes coil into short, dense rods called chromatids.
  • The ______are two genetically identical bodies joined together at a pinched spot called the centromere
  • The nuclear envelope disintegrates
  • Centrioles sprout microtubules called spindle fibers, which push the centrioles towards opposite poles
  • Metaphase is a phase in which the chromosomes line-up on the equator of the cell
  • The spindle fibers from opposite poles attach to the chromatids
  • Anaphase is a phase in which the two sister chromatids separate and are pulled by the spindle fibers towards opposite poles
  • The identical chromatids are now called ______chromosomes
  • Telophase is a phase in which the chromosomes are surrounded by a new nuclear envelope and the DNA uncoils to return to its dispersed form
  • Cytokinesis overlaps with telophase and is a process in which a crease (called a cleavage ______) begins to form and eventually pinches one cell into two