chapter 3 notes

Chapter 3: Cells & Tissues: Part I: Cells: The Living Units

1)    Cells (See Fig. 3.4)

a)   Definition- the building blocks of all living things

b)   Carry out all chemical activities needed to sustain life

c)   Cytology

d)   Tissues- groups of cells that are similar in structure and function

e)   Cell structure

i)    Cells are not all the same

ii)   They have three main regions

(1) Plasma membrane

(2) Cytoplasm

(3) Nucleus- stains darkly compared to the rest of the cell

2)   Cell (plasma) membrane

a)   Barrier for cell contents

b)   Selective permeability- only certain object pass through it

i)    The plasma membrane allows some materials to pass while excluding others

ii)   This permeability influences movement both into and out of the cell

c)   Living cells maintain chemical gradient

d)   Also contains proteins

e)   Structure – The Fluid Mosaic Model (See Fig. 3.2)

i)    Double Phospholipid bilayer

(1) Hydrophilic polar head ( = water loving)

(2) Hydrophobic nonpolar tails (= water fearing)

ii)   Glycolipids and cholesterol

iii)  Proteins

(1) Integral

(2) Peripheral

iv)  Microvilli: finger-like projections that increase surface are for absorption

f)   Membranes junctions

(1) Tight junctions

(a)  Impermeable junctions

(b) Bind cells together into leak proof sheets

ii)   Desmosomes (See Fig. 3.3)

(1) Anchoring junct5ions that prevent cells from being pulled apart

iii)  Gap junctions

(1) Allow communications between cells

3)   The cytoplasm- the material outside the nucleus and inside the plasma membrane

a)   Cytosol

i)    Fluid that suspends other elements

b)   Organelles

i)    Metabolic machinery of the cell

ii)   “Little organs” that perform functions for the cell

c)   Inclusions

i)    Chemical substances such as stored nutrients or cell products

d)   Cytoplasmic organelles

i)    Mitochondria (powerhouse of the cell)

(1) “Powerhouse” of the cell

(2) Change shape continuously

(3) Carry out reactions where oxygen is used to break down food

(4) Provides ATP for cellular energy

(5) Outer membrane

(6) Inner membrane = cristae

(7) Matrix

ii)   Ribosomes

(1) Made of protein and RNA

(2) Sites of protein synthesis

(3) Found at two locations

(a) Free ribosomes- free in the cytoplasm

(b) Bound ribosomes- As part of the rough endoplasmic reticulum

iii)  Endoplasmic reticulum – ER (endo=within; plasmic=cytoplasm; reticulum= network) (See Fig. 3.18)

(1) Fluid-filled tubules for carrying substances

(2) Two types of ER

(3) Rough ER – RER (Granular)

(a) Studded with ribosomes

(b) Synthesizes proteins

(4) Smooth ER – SER (Agranular)

(a) Functions in lipid metabolism and detoxification of drugs and pesticides

iv)  Golgi apparatus

v)   Lysosomes

vi)  Peroxisomes

vii) Cytoskeletal elements

(1) Microtubules

(2) Microfilaments

(3) Intermediate filaments

viii)      Centrosome and centrioles

ix)  Cellular extensions

(1) Cilia

(2) Flagella

4)   The nucleus

a)   Control center of the cell

b)   Nuclear envelope (membrane)

i)    Barrier of the nucleus

ii)   Double membrane

iii)  Contains nuclear pores that allow for exchange of material with the rest of the cell

iv)  Nucleoplasm

c)   Nucleoli:

i)    nucleus contains one or more nucleoli

ii)   Sites of ribosome assemble

iii)  Ribosomes migrate into the cytoplasm through nuclear pores

d)   Chromatin (“beads on a string”)

i)    Composed of DNA and protein

ii)   Present when the cell is not dividing

iii)  Scattered throughout the nucleus

iv)  Condenses to form chromosomes when the cell divides

v)   Nucleosome (beads)

(1) Histones

(2) Double – stranded DNA

e)   Transport across the plasma membrane

i)    Membrane transport- movement of substances into and out of the cell

ii)   Two basic methods of transport:

(1) Passive transport (See Fig. 3.10)- no energy is required

(a) Simple diffusion (See Fig. 3.9)

(i)  particles tend to distribute themselves evenly within a solution

(ii) movement is from high concentration to low concentration or “down a concentration gradient”

(iii)an unassisted process

(iv) solutes are lipid-soluble materials or small enough to pass through membrane pores

(b) Facilitated diffusion- substances require a protein carrier for passive transport

(i)  Transport lipid-insoluble and large substances

(c)  Osmosis (See Figs. 3.8 & 3.9)- simple diffusion of water through a membrane

(i)  Highly polar water molecules easily across the plasma membrane through aquaporins

(d) Solutions- homogeneous mixture of two or more components:

(i)  Solvent- dissolving medium, typically water in the body

(ii) Solutes- components in small quantities within a solution

(iii)Intracellular fluid- inside the cell

(iv) Interstitial fluid- fluid on the exterior of the cell

(v)  Hypertonic solution (hyper = greater than, above)

1.  Higher concentration of solutes and a lower concentration of water

(vi) Hypotonic solution (hypo = less than, under)

1.  Lower concentration of solutes and higher concentration of water

(vii)            Isotonic solution (iso = same)

(e) Filtration

(2) Active transport- cell must provide metabolic energy (ATP)

(a) Substances are transported that are unable to pass by diffusion

(b) Substances may be too large

(c) Substances mat not be able to dissolve in the fat core of the membrane

(d) Substances may have to move against a concentration gradient

(e) ATP is used for transport

(f) Na⁺/ K⁺ pump (See Fig. 3.11)

(g) Vesicular transport (See Fig. 3.5)

(i)  Exocytosis (Exo = out of; cyt = cell; osis = process)-

(ii) Endocytosis (Endo = into; cyt = cell; osis = process)

1.  Phagocytosis

2.  Pinocytosis

(3) Resting membrane potential

5)   Cell diversity: cells that-

a)   connect body parts (erythrocytes cells)

b)   cover and line body organs (epithelial cells)

c)   move organs and body parts (skeletal muscle cells and smooth muscle cells)

d)   store nutrients (fat cell)

e)   fight disease (macrophage)

f)   gathers information and controls body functions (nerve cell)

g)   reproduction (sperm cell)

6)   Cell growth and reproduction

a)   Cell life cycle

i)    Cells have two major periods

ii)   Interphase

(1) Cells grows

(2) Cells carries on metabolic process

b)   The cell cycle

i)    Interphase

(1) G₁ = growth phase

(2) S = Synthetic phase

(a) DNA replication = semiconservative replication (See Fig. 3.14)

(i)  Unwinding of double helix

(ii) Formation of replication fork

(iii)DNA polymerase

1.  leading strand

2.  lagging strand

(iv) Formation of 2 double helices

(3) G₂ = final phase of interphase

ii)   Cell division (See Fig. 3.15)

(1) Mitosis = Nuclear division

The phases of Mitosis:

(a) Prophase

(i)  Early prophase

(ii) Late prophase

(b) Metaphase

(c) Anaphase

(d) Telophase

(2) Cytokinesis = Cytoplasmic division

c)   Protein synthesis (See Figs. 3.16)

i)    Gene- DNA segment that carries a blueprint for building one protein

ii)   Proteins have many functions

(1) Building materials for cells

(2) Acts as enzymes (biological catalysts)

iii)  RNA is essential for protein synthesis

iv)  Basic terms

(1) Gene

(2) Genetic code

(3) Transcription

(4) Translation

v)   The role of RNA

(1) tRNA (transfer RNA)- transfers appropriate amino acids to the ribosomes for building the protein

(2) rRNA (ribosomal RNA)- helps form the ribosomes where proteins are build

(3) mRNA (messenger RNA)- carries the instructions for building a protein from the nucleus to the ribosome

vi)  Transcription

(1) Definition

(2) Steps

(a) mRNA formation

(b) Editing of mRNA

vii) Translation

Part II: Body Tissues: The Living Fabric

1)    Introduction

a)   Definition- groups of cell with similar structure and function

i)    Tissue

ii)   Histology

b)   Four Primary Types

i)    Epithelium

ii)   Connective tissue

iii)  Muscle

iv)  Nervous tissue

2)   Epithelial tissue

a)   Locations:

i)    Body coverings

ii)   Body linings

iii)  Glandular tissue

b)   Functions:

i)    Protection

ii)   Absorption

iii)  Filtration

iv)  Secretion

c)   Characteristics

i)    Cells fit closely together and often form sheets

ii)   The apical (top) surface is the free surface of the tissue

iii)  The lower surface of the epithelium rests on a basement membrane (like a glue)

iv)  Avascular- no blood supply

v)   Regenerative- easily if will nourished

vi)  Supported by connective tissue

d)   Classification of epithelia (See Fig. 3.17)

i)    Cellular shape

(1) Squamous- flattened

(2) Cuboidal- cube-shaped

(3) Columnar- column-like

ii)   Cellular arrangement (layers)

(1) Simple- one layer

(2) Stratified- more than one layer

e)   Simple Epithelia (See Fig. 3.18)

i)    Simple squamous epithelium- one layer of flat cells

(1) Usually forms membranes-

(a) Lines body cavities

(b) Lines lungs and capillaries

ii)   Simple cuboidal epithelium- one layer of cube-shaped cells

(1) Common in glands and their ducts

(2) Forms walls of kidney tubules

(3) Covers the ovaries

iii)  Simple columnar epithelium- one lay of column-like cells

(1) Often includes mucus-producing goblet cells

(2) Lines digestive tract

iv)  Pseudostratified columnar epithelium- single later but some cells are shorter than others

(1) Often look like a double layer of cells

(2) Sometimes ciliated, such as in the respiratory tract

(3) May function in absorption or secretion

f)   Stratified Epithelia (See Fig. 3.18)

i)    Stratified squamous epithelium- cells at the apical surface are flattened

(1) Found as a protective covering where friction is common

(2) Locations: skin, mouth, esophagus

ii)   Stratified cuboidal- two layers of cuboidal cells

iii)  Stratified columnar- surface cells are columnar cells underneath vary in size and shape

iv)  Stratified cuboidal and columnar-

(1) Rare in human body

(2) Found in many ducts and glands

v)   Transitional epithelium- shape of cells depends upon the amount of stretching

(1) Lines organs of the urinary system

g)   Glandular Epithelium

i)    Gland-  one or more cells responsible for secreting a particular product

ii)   Endocrine glands- ductless since secretions diffuse into blood vessels

(1) All secretions are hormones

iii)  Exocrine glands- secretions empty through ducts to the epithelial surface

3)   Connective tissue  (See Fig. 3.19)

a)   Found everywhere in the body

b)   Includes the most abundant and widely distributed tissues

c)   Functions:

i)    Binds body tissues together

ii)   Supports the body (bone)

iii)  Provides protection (blood- only fluid tissue in the body)

d)   Characteristics

i)    Variations in blood supply

ii)   Some tissue types are well vascularized

iii)  Avascular- have a poor blood supply (tendons and ligaments)

iv)  Common tissue of origin = mesenchyme

v)   Extracellular matrix: nonliving material that surrounds living cells

e)   Structural elements of connective tissue

i)    Ground substance- mostly water along with adhesion protein and polysaccharide molecules

ii)   Fibers- produced by the cells

(1) Collagen fibers- thick white fibers

(2) Elastic fibers- yellow fibers, thin, flexible

(3) Reticular fibers- midsized collagen-like

iii)  Cells

(1) Fibroblasts- cells that make fibers

(2) Chondroblasts

(3) Osteoblasts

(4) Hematopoeitic stem cell

f)   Types

i)    Mesenchyme

ii)   Connective tissue proper

(1) Areolar connective tissue-

(a) Loose connective tissue

(b) Most widely distributed

(c) Soft pliable tissue like “cobwebs”

(d) Packing tissue around organs and under skin

(e) Contains all fiber types

(f) Can soak up excess fluid (causes edema)

(2) Adipose connective tissue-

(a) Loose connective tissue

(b) Matrix- fat globules predominate

(c) Many cells contain large lipid deposits

(d) Functions- insulates the body, protects some organs (eyes), serves as a site of fuel storage

(3) Reticular connective tissue-

(a) Loose connective tissue

(b) Delicate network of interwoven fibers

(c) Forms stroma (internal supporting network) of lymphoid organs

(d) Lymph nodes

(e) Spleen

(f) Bone marrow

(4) Dense regular connective tissue (dense fibrous tissue)

(a) Main matrix elements is collagen fiber

(b) Fibroblasts are cells that make fibers

(c) Locations-

(i)  Tendons- attach skeletal muscle to bone

(ii) Ligaments- attach bone to bone at joints

(iii)Dermis- lower layers of the skin

iii)  Cartilage

(1) Characteristics

(2) Types

(a) Hyaline cartilage- most common type of cartilage

(i)  Composed of- abundant collagen fibers, rubbery matrix

(ii) Found in the larynx

(iii)Entire fetal skeleton prior to birth

(b) Elastic cartilage-

(i)  provides elasticity

(ii) Supports the external ear

(c) Fibrocartilage-

(i)  Highly compressible to absorb shock

(ii) Highly compressible to absorb shock

(iii)Forms cushion- like discs between vertebrae

iv)  Bone = Osseous tissue

(1) Used to protect and support the body

(2) Composed of:

(a) Bone cells in lacunae (cavities)

(b) Hard matrix of calcium salts

(c) Large number of collagen fibers

v)   Blood (See Fig. 4.9 k)

4)   Nervous tissue (See Fig. 3.21)

a)   Composed of neurons and nerve support cells

b)   Function is to send impulses to other areas of the body:

i)    Irritability (cranky, disruption, change)

ii)   Conductivity

c)   Types of cells

i)    Neurons

ii)   Supporting cells

5)   Muscle tissue (See Fig. 3.20)

a)   Function is to produce movement

b)   Types

i)    Skeletal muscle-

(1) under voluntary control

(2) controls to pull on bones or skin

(3) produces gross body movements or facial expressions

(4) characteristics of skeletal muscle cells: striated (striped)

(5) multinucleate (more than one nucleus)

(6) long, cylindrical

ii)   Cardiac muscle-

(1) under involuntary control

(2) found only in the heart

(3) function is to pump blood

(4) characteristics of cardiac muscle cells-

(a) cells are attached to other cardiac muscle cells at intercalated disks

(b) striated

(c) one nucleus per cell

iii)  Smooth (visceral) muscle-

(1) Under involuntary muscle

(2) Found in walls of hollow organs such as stomach, uterus, and blood vessels

(3) Characteristics of smooth muscle cells:

(4) No visible striations

(5) One nucleus per cell

(6) Spindle shaped cells

iv)  Tissue repair (wound healing)

(1) Regeneration:

(a) Replacement of destroyed tissue by the same kind of cells

(2) Fibrosis-

(a) Repair by dense (fibrous) connective tissue (scar tissue)

(3) Neoplasm- new growth, benign or malignant

(4) Hyperplasia- fast growth due to local stimulation

(5) Atrophy- decrease in size