Chapter 3 & 4 Cells & Tissues

Cells Cells vary in size and shape; all are microscopic All cells share general structures Cells are organized into three main regions Nucleus Cytoplasm Plasma membrane Organelles are specialized structures with the cytoplasm

Plasma Membrane Forms outer boundary Composed of thin, two-layered membrane of phospholipids and embedded with proteins Is selectively permeable

Cytoplasm Material outside the nucleus and inside the plasma membrane Cytoskeleton internal framework of cell Made up of microfilaments and microtubules Provides support and movement of cell and organelles

Organelles

Ribosomes Made of protein and RNA Manufactures enzymes and other proteins Often called “protein factories” Found at two locations Free in the cytoplasm Attached to rough endoplasmic reticulum

Endoplasmic Reticulum (ER) Network of connecting sacs and canals Carry substances through cytoplasm Two Types Rough ER Collects folds, and transports proteins made by ribosomes Smooth ER Manufactures fats, carbohydrates, proteins that make up cellular membrane

Golgi Apparatus Group of flattened sacs near nucleus Chemical processing and packaging center Collects chemicals into vesicles (little sacs) that move from the smooth ER outward to the plasma membrane

Mitochondria Composed of inner and outer membranous sac “Powerhouses” of the cell Involved with energy-releasing chemical reactions (cellular respiration) Uses this released energy to “recharge” ATP required for cellular work Each contains one DNA molecule

Lysosomes Membrane enclosed packets containing digestive enzymes Have protective functions (eat microbes)

Centrosome Microtubule-organizing region near the nucleus Plays important role in organizing and moving structures within the cell Centrioles – lie at right angles to each other with the centrosome Function in moving chromosomes during cell reproduction

Cell Extensions Microvilli – small, fingerlike projections that increase surface are and ability to absorb substances (small intestines) Flagellum – single projection that propels the male sperm cell Cilia - hairlike extensions Move materials across the cell surface (respiratory tract or reproductive tubes) Some serve sensory functions

Nucleus Contains most of genetic code (genome) instructions for making proteins, which determine cell structure and function Nuclear envelope – 2 separate membranes that allow molecules to move in and out of the nucleus Nucleoplasm – a type of protoplasm that fills the nucleus Nucleolus – dense region of the nucleus where the cell makes the subunits that form ribosomes Chromatin and chromosomes – chromatin granules in the nucleus made up of DNA 46 nuclear chromosomes contain DNA, which contains genetic code

Cell Structure and Function Every human cell has a designated function, some help maintain the cell, others regulate life processes Specialized functions differ depending on the number and type of organelles

Quick Check Describe the structure of the plasma membrane of the cell? What is cytoplasm? What does it contain? List five major structures of the cell and briefly describe their function.

Solutions and Transport Solution – homogeneous mixture of two or more components Solvent – dissolving medium Solutes – components in smaller quantities within a solution Intracellular fluid – fluid within the cell Interstitial fluid – fluid outside of the cell

Movement of Substances Through Cell Membrane Cell membrane must permit movement of substances into and out of the cell Selective Permeability – ability to allow some materials to pass while excluding others Achieved by two basic methods Passive transport No energy is required Active transport Requires energy – breakdown of ATP and the use of released energy is required

Passive Transport Processes Diffusion Substances scatter themselves evenly throughout an available space Particles from and area of high concentration to an area of lower concentration, or down a concentration gradient

Passive Transport Processes Osmosis Diffusion of water through a selectively permeable membrane (when some solutes cannot cross the membrane)

Passive Transport Processes Filtration Movement of water and small solute particles, but not larger particles, through a filtration membrane Movement caused by hydrostatic pressure on one side (higher pressure to area of lower pressure)

Active Transport Processes Uphill movement of substances through a living membrane Movement of substances is “up the concentration gradient” Requires energy from ATP

Ion Pumps Protein structures in the cell membrane called a carrier that use energy from ATP Specific to one type of ion Some work with others to transport glucose, amino acids, other substances Example: Calcium pumps in muscle cells Sodium-potassium pumps

Phagocytosis “Cell eating” – large particles are engulfed in a vesicle as a protective mechanism Often used to destroy bacteria or debris from tissue damage

Pinocytosis “Cell drinking” – engulfs fluids or dissolved substances into cells Requires ATP to move the cytoskeleton in a way that engulfs material and pulls it into the cell

Quick Check What is the difference between a passive transport and an active transport process? What is osmosis? What is filtration? How does an ion pump work? Is it active or passive? Describe the process of phagocytosis. Describe the process of pinocytosis.

Cell Reproduction and Heredity Mitosis – process of cell reproduction Cell divides to form two cells Closely tied to the production of proteins Two nucleic acids play a crucial role Ribonucleic acid (RNA) Deoxyribonucleic acid (DNA)

DNA Structure Large spiral-shaped molecule Sugar (deoxyribose) and phosphate units make up the sides Base pairs (adenine-thymine or guanine-cytosine) compose the ‘steps’ Base pairs always the same but the sequence differs in different DNA molecules This is important because the sequence determines heredity

DNA and Genetic Information Gene – specific sequence of base pairs within a DNA molecule Dictate formation of enzymes and other proteins by ribosomes Indirectly determine a cell’s structure and function Determines inherited traits

Genetic Code Genetic information is stored in base-pair sequences on genes and directs the synthesis of a specific protein RNA molecules and protein synthesis DNA – contained in cell nucleus Protein synthesis occurs in cytoplasm. Genetic information must pass from the nucleus to the cytoplasm. Requires transcription and translation.

Transcription Double-stranded DNA separates to form messenger RNA (mRNA) Each strand of mRNA duplicates a particular gene from a segment of DNA mRNA molecules pass from the nucleus to the cytoplasm where they direct protein synthesis in ribosomes and ER

Translation Involves synthesis of proteins in cytoplasm by ribosomes Requires the use of information contained in mRNA Codon – a series of three nucleotide bases that acts as a code for a specific amino acid

Protein Synthesis

Cell Life Cycle Cells have two major periods Interphase Cell grows Cell carries on metabolic processes Cell division Division of the nucleus (mitosis) and cytoplasm resulting in two identical daughter cells

Mitosis

Prophase – first stage Chromatin granules become organized Chromosomes (pairs of linked chromatids) appear Centrioles move away from nucleus Nuclear envelope disappears, freeing genetic material Spindle fibers appear

Metaphase – second stage Chromosomes align across center of cell Spindle fibers attach themselves to each chromatic

Anaphase – third stage Centromeres break apart Separated chromatids now called chromosomes Chromosomes are pulled to opposite ends of the cell Cleavage furrow develops at end of anaphase

Telephase – fourth stage Cell division is completed Nuclei appear in daughter cells Nuclear envelope and nucleoli appear Cytoplasm is divided (cytokenesis) Daughter cells become fully functional

Results of Cell Division Two identical cells result from cell division, growing tissues or replacing old or damaged cells Differentiation – process by which daughter cells can specialize and form different kinds of tissue Abnormalities of mitotic division can produce benign or malignant neoplasms (tumors)

Body Tissues Cells are specialized for particular functions Tissues: Groups of cells with similar structure and function Four primary types Epithelium Connective tissue Nervous tissue Muscle

Epithelial Tissue Found in different areas Functions Body coverings Body linings Glandular tissue Functions Protection Absorption Filtration Secretion

Classification of Epithelial Cells Shape of cells Squamous – flattened Cuboidal – cube-shaped Columnar – column-like Transitional – (varying shapes that can stretch)

Classification of Epithelial Tissue Number of cell layers Simple – one layer Stratified – more than one layer

Simple Squamous Epithelium Single layer of flat cells Lines body cavities Lines lungs & capillaries Substances can readily pass through, making transportation its special function Ex. Absorption of oxygen into the blood

Stratified Squamous Epithelium Cells at the free edge are flattened Found as a protective covering where friction is common Locations Skin Mouth Esophagus

Simple Columnar Epithelium Single layer of tall cells Often includes goblet cells, which produce mucus Lines digestive tract

Stratified Transitional Epithelium Shape of cells depends upon the amount of stretching Lines and protects organs of the urinary system

Pseudostratified Epithelium Single layer, but some cells are shorter than others Often looks like a double cell layer Sometimes ciliated, such as in the respiratory tract May function in absorption or secretion

Simple Cuboidal Epithelium Single layer of cube-like cells Common in glands and their ducts Forms walls of kidney tubules Covers the ovaries

Connective Tissue Found everywhere in the body Includes the most abundant and widely distributed tissues Functions Binds body tissues together Supports the body Provides protection

Connective Tissues Variations in blood supply Extracellular matrix Some tissue types are well vascularized Some have poor blood supply or are avascular Extracellular matrix Non-living material that surrounds living cells

Aerolar Tissue Also known as loose connective tissue Most widely distributed connective tissue Makes up fascia – the fibrous material that helps to bind skin, muscles, bones and other organs Some made of collagen – a strong by flexible fibrous protein Some made of elastin – a stretchy fiber

Adipose Tissue Matrix is an areolar tissue in which fat globules predominate Many cells contain large lipid deposits Functions Insulates the body Protects some organs Serves as a site of fuel storage

Reticular Tissue Delicate network of interwoven fibers Forms internal supporting network of lymphoid organs Lymph nodes Spleen Bone marrow

Dense Fibrous Tissues Thick bundles of strong collagenous fibers Arranged in parallel rows Strong and flexible, but do not stretch Examples: Tendon – attach muscle to bone Ligaments – attach bone

Bone Tissue Also known as osseous tissue Hard and calcified Forms structural building blocks called osteons or Haversian systems Protect and support the body Storage of calcium

Cartilage Tissue Matrix has consistency of a firm plastic or gristle like gel Cartilage cells, called chrondocytes, are located in the many tiny spaces throughout the matrix

Blood and Hematopoietic Tissue Blood cells (red and white) surrounded by fluid matrix Functions include transportation and protection Hematopoietic Tissue Bloodlike connective tissue found in the red marrow cavity of bones and in the spleen, tonsils, and lymph nodes

Quick Check What are the 4 main types of tissues? How are epithelial cells classified by shape? What is the difference between simple and stratified tissue?

Muscle Tissue Function is to produce movement Greater ability to contract than other tissue Three types Skeletal muscle Cardiac muscle Smooth muscle

Skeletal Muscle Can be controlled voluntarily Cells attach to connective tissue Cells are striated More than one nucleus

Cardiac Muscle Found only in the heart Cells attached to other cardiac muscle cells at intercalated disks Function is to pump blood Involuntary Cells are striated One nucleus per cell

Smooth Muscle Also known as visceral muscle Involuntary muscle Attached to other smooth muscle cells Surrounds hollow organs and blood vessels No visible striations One nucleus per cell

Nervous Tissue Function is rapid communication between body structures Nerve cells, or neurons, and nerve support cells called glia, or neuroglia All have: Cell body 1 axon - transmits impulse away from the cell body 1 or more dendrites – carry impulses toward cell body

Quick Check List and describe 4 types of connective tissues. List and describe the 3 types of muscle tissue. What are the 2 types of processes found on nervous tissue? What is their function?