Download Outline 2 - human anatomy

Human Anatomy
Lecture 2
Study of Cells
 Cell shapes and sizes
o 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
o 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
o 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
o 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.
o 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
o Plasma membrane – forms the surface boundary of the cell
o 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
o Nucleoplasm – material within the ___________________
Cell Surface
 Plasma membrane – essentially a two-layered lipid film with proteins embedded
in it
o Membrane Lipids
 Phospholipids make up 75% of the membrane lipid molecules
 Two fatty acid tails are __________________________,
while the phosphate-containing head is hydrophilic.
o The tails orient away from the water, while the
heads orient towards the intracellular fluid and
extracellular fluid
o The molecules drift from place to place, keeping the
membrane _____________
o Fat soluble substances pass in and out of the cell
through this phospholipid bilayer
o 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
o ______________________ – 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
o 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
o Osmosis – the diffusion of water through a selectively permeable
membrane, from the side where water is more concentrated to where water
is less concentrated
o 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
o 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
o 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
o The coating cushions the plasma membrane and protects it from
________________
o The coating functions in cell identity (distinguishing cells from diseased
cells or invading organisms)
o The coating contains cell-adhesion molecules that help bind tissues
together
Microvilli, Cilia, and Flagella
o Microvilli- extensions of the plasma membrane that increase surface area
o 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
o Flagella- long whiplike tails for movement of sperm cells

Intercellular Junctions – arrangements of proteins that link cells together and
attach them to extracellular material
o Tight Junctions- A zipperlike junction between epithelial cells that limits
the passage of substances between them
o _____________________ -A patchlike intercellular junction that
mechanically links two cells together
o 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
o The nucleus – round or oval shaped structure near the center of the cell
containing DNA
o ______________________ 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)
o Ribosomes – Granules composed of ribosomal RNA and enzymes that
read sequences of messenger RNA to assemble sequences of amino acids
to make proteins
o _____________Complex – Organelle that modifies and packages newly
synthesized proteins and synthesizes carbohydrates
o Lysosomes – Organelles that contain enzymes that are used to digest
foreign matter, pathogens, and expired organelles
o Peroxisomes – Organelles containing enzymes that detoxify drugs and
break down fatty acids, producing hydrogen peroxide in the process
o ______________________ – Organelles specialized to synthesize ATP
(for energy)
o Centrioles- Organelles composed of a short cylinders of microtubules, that
are the origin of the mitotic spindles (used in cell division)
o 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
o Meiosis – the production of egg and sperm cells (haploid cells)
o 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.
o The _____________________ are two genetically
identical bodies joined together at a pinched spot
called the centromere
o The nuclear envelope disintegrates
o 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
o 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
o 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