Unit 2

Cells and Tissues

Membrane Transport

• Membrane Transport: movement of substances in and out of the cell to maintain homeostasis

• Transport is by two basic methods– Passive Transport

• No energy is required– Active Transport

• Cell must provide metabolic energy (ATP)• The membrane doesn’t let everything through –

selective permeability

Passive Transport Processes

• Diffusion– Particles distribute evenly through

solution– Movement is from high concentration to

low concentration

Passive Transport Processes– Types include:

• Simple diffusion: solutes pass directly through plasma membrane

• Osmosis: diffusion of water (solvent) from an area with little solute (high concentration of water) to an area with high solute (low concentration of water)

• Facilitated diffusion: need a protein carrier to move through

(d) Osmosis, diffusion through a specific channel protein (aquaporin) or through the lipid bilayer

Lipidbilayer

Watermolecules

Lipid-insolublesolutes

(b) Carrier-mediated facilitated diffusion via protein carrier specific for one chemical; binding of substrate causes shape change in transport protein

Extracellular fluid

Cytoplasm

Lipid-solublesolutes

(a) Simple diffusion directly through the phospholipid bilayer

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

Passive Transport Processes

• Filtration

– Water & solutes forced through a membrane by pressure

– Pushed from area of high pressure to low pressure

Active Transport Processes

• Transport substances that are unable to by diffusion

• Reasons include:

– Too large

– Not able to dissolve in fatty acid core of membrane

– Need to move against concentration (from low to high)

Active Transport Processes

• Solute pumping

– Amino acids, some sugars, and ions transported this way

– ATP energizes protein carriers to move substances against concentration

– Ex: sodium-potassium pumphttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

Active Transport Processes

• Bulk Transport (2 Types)

– Exocytosis

• Moves materials out of cell in a membranous vesicle

Active Transport Processes

– Endocytosis• Moves materials

into a cell in a membranous vescicle

• Includes Phagocytosis (cell eating) and Pinocytosis (cell drinking)

Cell Diversity

• So far, we have looked at an “average” human cell

• However, cells vary greatly in size, shape, and function!

Types of Cells

• Cells that connect body parts

– Examples…

• Fibroblasts have Rough ER & Golgi to make fiber proteins

• Erythrocytes need room for pigment, so no organelles

Types of Cells

• Cells that cover and line body organs

– Ex: Epithelial Cells

• Shape allows packing together

Types of Cells

• Cells that move organs and body parts

– EX: Skeletal Muscle & Smooth Muscle

• Elongated so they can contract

Types of Cells

• Cells that store nutrients

– EX: Fat cell

• Cells that fight disease

– EX: Macrophage cell

• Has “false feet” to move to infection sites, lysosomes to digest harmful substances

Types of Cells

• Cells that gather information & control body functions

– EX: Nerve cell

• Long processes for sending & receiving messages

Types of Cells

• Cells of Reproduction

– EX: Oocyte (female egg)

• Many copies of organelles for distribution to daughter cells

– EX: sperm (male)

• Flagellum used in movement

Tissues

• Tissues: a group of cells with similar structure and function

• Histology: the study of tissues

• There are 4 primary types of tissues:– Epithelium = covering– Connective = support– Muscle = movement – Nervous = control

Epithelial Tissue

• Found in:– Body coverings– Body linings– Glands

• Function:– Protection– Absorption– Filtration– Secretion

Epithelial Tissues

• Characteristics:– Cells fit closely together– Tissue always has one free surface (apical

surface)– Lower surface (basal surface) bound by a

basement membrane (network of fibers/connective tissue)

– Regenerate easily

Classification of Epithelium

• Number of cell layers

– Simple: one layer

– Stratified: two or more layers

– Pseudostratified: uneven layers

Classification of Epithelium

• Shape of Cells

– Squamous: flattened

(squamous = thin, easily removed)

– Cuboidal: cube-shaped

– Columnar: column-like

• Combinations of these terms give us our specific Epithelium types

Types of Epithelium

• Simple Squamous– Description: Single layer

of flat cells– Function: Usually forms

membranes that allow diffusion and filtration

– Present in:• Lining of body

cavities• Lining of lungs and

capillaries

Types of Epithelium

• Simple Cuboidal

– Description: Single layer of cube-like cells

– Function: allow secretion and absorption

– Present in:

• Kidney tubules

• Ducts of glands

• Ovary surface

Types of Epithelium• Simple Columnar

– Description: Single layer of tall cells• Many have cilia or microvilli• Will often have “goblet cells”

– secrete mucus– Function: Absorption and

Secretion– Present in:

• Digestive tract, gallbladder• Ciliated: uterus, bronchi of

lungs

Types of Epithelium

• Pseudostratified Columnar– Description: Single layer of

cells with different heights• Many have cilia or

microvilli• Will often have “goblet

cells” – secrete mucus– Function: secretion and

propulsion of mucus– Present in:

• Sperm-carrying ducts • Trachea

Types of Epithelium

• Stratified Squamous– Description: Layers of

cells, cells at the free edge are flattened

– Function: Protection of underlying areas where friction is common

– Present in:• Skin• Mouth• Esophagus

Types of Epithelium

• Stratified Cuboidal*– Rare in the body, typically 2 cell-layers thick,

found in some sweat and mammary glands

• Stratified Columnar*– Limited distribution in the body; surface cells

are columnar, and cells underneath vary in size and shape; occurs at transition areas between 2 types of epithelium

*Won’t need to identify picture

Types of Epithelium

• Transitional Epithelium– Description:

combination of types of cells

– Function: stretching– Present in: bladder

Types of Epithelium• Glandular*

– Gland: one or more cells that make and secrete a particular product

– Two major gland types:• Endocrine gland

– Ductless– Secretions are hormones

• Exocrine gland– Empty through ducts onto body surfaces (skin) or

into body cavities– Secretions are sweat and oil– More numerous than endocrine

*Won’t need to identify picture

Connective Tissue

• Found in: – All areas of the body– Most abundant type of tissue!

• Function:– Binds body tissues together– Supports body– Provides protection

Connective Tissue

• Characteristics:– Underlies epithelium– The cells are in a fiber MATRIX – there’s lots

of non-living material that surrounds the living cells

– Types include Bone, Cartilage, Dense Connective, Loose Connective, and Blood

Types of Connective Tissue

• Bone– Description:

• Bone cells in cavities• Hard matrix of calcium

salts• Large amount of

collagen fibers– Function: used to protect

and support the body

Types of Connective Tissue• Cartilage:

– Three types…

• Hyaline cartilage

– Keeps bones from rubbing together

– Has abundant collagen fibers and a rubbery matrix

– Most common cartilage

– Entire fetal skeleton is hyaline cartilage

– Found at end of long bones, rib cartilage, trachea, nose

Types of Connective Tissue

• Elastic Cartilage– Provides elasticity– EX: external ear, epiglottis

• Fibrocartilage– Highly compressible– EX: cushion disks between vertebrae, pubic

symphysis, knee joint discs

Types of Connective Tissue

• Dense (Fibrous) Connective– Description:

Contains LOTS of collagen fibers

– EX: Tendons (attach muscle to bone) and Ligaments (attach bone to bone)

Types of Connective Tissue

• Loose Connective– Areolar

• Soft, pliable• Usually found under

epithelium– Reticular

• Interwoven fibers that support lots of cells

• Found in lymph nodes, spleen, and bone marrow

Types of Connective Tissue

• Blood– Surrounded by fluid

matrix (plasma)– Functions as the

transport vehicle for materials (gases, nutrients, wastes, etc.)

– Includes erythrocytes (Red Blood Cells) and Leukocytes (White Blood Cells)

Muscle Tissue

• Found in: Muscles! DUH!

• Function: Produce movement

• Characteristics: – Properties include elasticity and contractility– Three types…

Muscle Tissue Types

• Skeletal Muscle– Description:

• Cells are striated• Cells have more

than one nucleus• Cells attach to

connective tissue– Function:

• Voluntary control of muscles

Muscle Tissue Types

• Cardiac Muscle– Description:

• Cells are striated• Cells have one nucleus• Cells attached to other

cardiac muscles• Has Intercalated disks

– Function:• Pump blood involuntary

Muscle Tissue Types

• Smooth Muscle– Description:

• Cells are not striated• Cells have one nucleus• Cells attach to other

smooth muscle cells– Function:

• Surround hollow organs• Function involuntarily

Nervous Tissue

• Found in: Brain, Spinal Cord, Nerves• Function: Send and receive impulses from

other areas of the body

Motor Unit! (Includes Muscle)

Tissue Repair

• Can happen two ways…– Regeneration: replacement of destroyed

tissue by the same kind of cells– Fibrosis: repair by dense fibrous connective

tissue (scar tissue)

• Type of repair determined by type of tissue damaged, and by severity of the injury

Tissue Repair

• Tissues that regenerate easily:– Epithelial Tissue– Fibrous Connective Tissue & Bone

• Tissues that regenerate poorly:– Skeletal Muscle Tissue

• Tissues mainly replaced with scar tissue:– Cardiac Muscle Tissue– Nervous Tissue within brain & spinal cord