BIO Ch 3: Cells & Tissues

cell membrane

A plasma structure that encloses the cytoplasm, forming a selective outer boundary between intracellular and extracellular materials; phospholipid bilayer

cytoplasm

A jelly-like substance filling the internal space of the cell that safely suspends and holds all cellular organelles

organelles

Specialized structures inside cells that perform distinct, essential metabolic and synthesis functions

• nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, mitochondria, cytoskeleton, centrioles, cilia, flagella, and microvilli

phospholipid bilayer

Phospholipids align in a double layer to form the membrane's core structure, featuring two distinct regions

• polar head

• non-polar tail

inside

Are these vital compounds and ions maintained at higher concentrations inside the cell or outside?

• Enzymes

• Glycogen

• Potassium

outside

Are these vital compounds and ions maintained at higher concentrations inside the cell or outside?

• Sodium

• Calcium

• Chloride

direct passage

Type of cell membrane passage:

Some substances, like O₂ and CO₂, can pass directly through the cell membrane’s phospholipid bilayer

protein channels

Type of cell membrane passage:

Some substances must pass through transmembrane protein channels, such as Na⁺ through its channels

carrier molecules

Type of cell membrane passage:

Some substances require carrier molecules to transport them across the cell membrane, such as glucose

vesicular transport

Type of cell membrane passage:

Some substances require vesicular transport across the membrane. The vesicle must fuse with the cell membrane for transport

passive transport

Type of transportation that does not require the cell to expend energy. Substances move down their concentration gradient.

E.g., diffusion, osmosis, and facilitated diffusion

active transport

Type of transport that requires the cell to expend energy, usually in the form of ATP, to transport substances.

diffusion

The movement of substances down a concentration gradient from high to low concentration; passive

solution

solutes + solvent = ?

solutes

Substances dissolved in a predominant liquid or gas, such as ions or molecules

solvent

The predominant liquid or gas in which the solute is dissolved

osmosis

The diffusion of water (a solvent) across a selectively permeable membrane from a region of higher water concentration to one of lower water concentration

Passive; does not require ATP

osmotic pressure

The force required to prevent the movement of water across a cell membrane

• Depends directly on the difference of solution concentrations inside a cell relative to outside the cell

hypotonic

The solution has less solute and more water

The cell has more solute and less water

Water moves in, causing the cell to swell.

isotonic

Equal solute concentrations inside and around the cell.

The cell will neither shrink nor swell

hypertonic

The solution has more solute and less water.

The cell has more water and less solute.

Water moves out, causing the cell to shrink.

facilitated diffusion

A carrier-mediated transport process that moves substances their concentration gradient (from higher to lower concentration).

No ATP required

• Membrane channels; carrier molecules

leak channels

Membrane channels that constantly allow ions to pass through

• Facilitated diffusion

gated channels

Membrane channels that limit the movement of ions across the membrane by opening and closing

• Facilitated diffusion

carrier molecules

Specialized proteins within the cell membrane involved in transport:

Move water-soluble molecules or ions across the membrane.

They exhibit specificity; only specific molecules are transported by the carriers

• Facilitated diffusion

active transport

A carrier-mediated process requiring ATP energy that moves substances across the cell membrane

• Against gradient (moves from lower to higher concentration)

• Ex. sodium potassium pump in cell membranes

sodium potassium pump

Moves Na⁺ out of cells and K⁺ into cells.

• Creates higher Na⁺ outside and higher K⁺ inside

• Primary example of active transport

vesicle

A small spherical sac formed by budding off from a membrane

• A type of active transport

endocytosis

Type of active transport where materials move into a cell in a vesicle formed from the plasma membrane

exocytosis

Type of active transport where vesicles fuse with the plasma membrane, releasing their contents into the extracellular fluid

transcytosis

An active process that is a combination of endocytosis and exocytosis

centrosome

• Organelle located near the nucleus

• Consists of two centrioles and pericentriolar material

• Function: organize mitotic spindle during cell division

cilia

Short, hair-like projections from the cell surface.

• Moves fluids along a cell surface

flagella

Longer than cilia, built to move an entire cell

• Only human example is the sperm cell’s tail

ribosome

Organelle that is the site of protein synthesis

endoplasmic reticulum

A continuous network of membranes forming flattened sacs or tubules that extend throughout the cytoplasm

• smooth, rough

rough er

Organelle Studded with Ribosomes

• Connected directly to the nuclear envelope

• Forms a series of flattened, factory-like sacs

• Mainly produces, folds, and processes various proteins

smooth er

No Ribosomes

• Extends from rough ER to form a network of tubules

• Synthesizes essential lipids, fatty acids, and steroids

• Detoxifies harmful drugs and metabolic byproducts

golgi aparatus

A cellular organelle consisting of 3–20 flattened, membranous sacs called cisternae

Protein Processing Center

• Modify, sort, and package proteins for transport to different destinations.

• Proteins are transported by various specialized vesicles.

lysosomes

Vesicles that form from the Golgi complex and contain powerful digestive enzymes

mitochondria

The “powerhouses” of the cell, responsible for ATP generation

• Generate ATP (cellular energy).

• More prevalent in highly active cells like muscles, liver, and kidneys.

• Have inner and outer membranes structurally similar to the plasma membrane.

peroxisomes

Organelles that contain enzymes that break down fatty acids, amino acids, and hydrogen peroxide

cytoskeleton

Organelle that consists of protein structures that support the cell, hold organelles in place, and enable the cell to change shape

• microtubules, microfilaments, and intermediate filaments

nucleus

Large organelle usually located near the center of the cell

• contain 23 pairs of chromosomes (consist of DNA and proteins)

centrioles

specialized area of cytoplasm close to the nucleus where microtubule formation occurs

microvilli

Specialized extensions of the cell membrane that are supported by microfilaments

• Finger-like projections that increase surface area

• They optimize absorption and secretion in the GI tract and kidney

gene expression

Biological process where the instructions in our DNA are converted into a functional product, like a protein or a functional RNA molecule

• “Protein synthesis”

• Cells transform genetic information encoded in genes (DNA) into RNA.

  • Occurs in the nucleus

• The RNA must be translated into a specific sequence of amino acids.

  • Occurs in cytoplasm

cellular metabolism

The metabolic processes that convert biochemical energy to ATP and produce waste products

• aka: cellular respiration

tissue

a group of cells that work together to perform a common function

• All cells derived from the same embryonic tissue

• Broadly classified into four major types

• Most organs contain all four types 

histology

the study of the microscopic anatomy of cells and tissues – it is a branch of pathology

pathologist

physicians who specialize in laboratory studies of cells and tissues,  aid other physicians in making diagnoses; they also perform autopsies

ephithelial, connective, muscle, nervous

what are the four types of tissue?

epithelial tissue

Tissue composed primarily of closely packed cells with very little intercellular material

• Covers and lines both internal and external body surfaces

• Functions: protection, absorption, or secretion

  • Exhibits a high mitotic rate, allowing for rapid and continuous cell replacement

  • Has a rich nerve supply (innervated) but lacks blood vessels (avascular), relying on underlying tissue for nutrients

  • Some specialized epithelial cells group together to form glands

layers, shape, surface specializations

Epithelial tissues are classified in three ways…?

simple epithelium

• Single layer of cells attached to the basement membrane 

• Best for absorption and secretion

stratified epithelium

• Two or more layers of cells

• Protects underlying tissues

• Nutrients must diffuse from BVs in underlying CT

squamous

cell shape that is flattened scale-like cells

cuboidal

cell shape that is round or cube-shaped with a circular nucleus

columnar

cell shape that is tall rectangular cells with elliptical nucleus

simple squamous epithelium

• A single layer of flattened cells in direct contact with the basement membrane

• Functions: Diffusion, excretion, and absorption

• Locations: Alveoli of lungs; Capillaries

simple cuboidal epithelium

• A single layer of cube-shaped cells resting on the basement membrane

• Functions: Excretion and absorption

• Locations: Kidney, Thyroid

simple columnar epithelium

• A single layer of tall flattened cells in direct contact with the basement membrane

• Functions: Secretion and absorption. 

• Locations: Gastrointestinal tract

stratified squamous epithelium

• Epithelium composed of several layers of flattened cells

• Bottom cells may be cuboidal, but top cells are squamous

• Two types: Keratinized and Non-keratinized

• Functions: protection from abrasion and desiccation (drying out)

• Locations: Skin, esophagus, vagina

stratified cuboidal epithelium

• Two or more layers of cuboidal cells

• Functions: protect the underlying tissues and organs from physical and microbial damage

• Locations: sweat glands, mammary glands

stratified columnar epithelium

• Two or more layers; top cells are columnar

• Functions: protects underlying tissues and organs from physical and microbial damage

• Locations: pharynx, epiglottis, salivary glands

pseudostratified ciliated columnar epithelium

Appears to be stratified, but all cells are touching basement membrane 

• Functions: Secretion and transport of mucus

• Locations: respiratory tract

transitional epithelium

• Apical (top) cells change shape from cuboidal to squamous when stretched

• Functions: lines urinary bladder

• Locations: urinary bladder

gap junction

provide passageways for chemicals to move between cells

• Found in skin and cardiac muscle

tight junctions

prevent the movement of material between cells

• Found in kidney and several other locations

desmosomes

link epithelial cells to surrounding structures (e.g., other cells & BM)

• Found in most epithelial tissue

exocrine glands

Have a duct to a body surface

• Sweat glands

• Sebaceous glands

• Secretory glands in GI Tract

endocrine glands

Lack a duct; secrete hormones

• Thyroid

• Pituitary

• Adrenal glands

• Gonads

exocrine, endocrine

what are the two types of glandular epithelium?

merocrine, apocrine, holocrine

what are the three types of exocrine glands?

merocrine glands

Most common gland. Secreting products via vesicles.

• Salivary and Sweat Glands

apocrine glands

Secrete by pinching off the apical surface of the glands.

• Mammary, Axillary, and Pubic Glands

holocrine glands

Whole cell ruptures to become secretory product.

• Sebaceous glands

sebaceous glands

Type of holocrine glands that are destroyed after releasing their contents. New glandular cells form to replace the cells that are lost

connective tissue

• Location: Usually found directly beneath epithelial tissue.

• Composition: Made up mostly of non-cellular material (matrix).

• Vasculature: Many are vascular (e.g., bone) but some are not (e.g., cartilage).

• Classification: Grouped into two major types: CT Proper and Specialized

• Functions: Support & bind, energy storage, reducing friction, carrying oxygen, immune defense

cells, protein fibers, ground substance

What are the three components of connective tissue?

fibroblasts

Connective tissue cell type that secretes protein fibers

• Produces matrix for connective tissue

macrophage

Connective tissue cell type that eats foreign cells

lymphocyte

connective tissue cell type that provides immune defense

mast cells

connective tissue cell type that causes inflammation

adipocyte

connective tissue cell type that stores energy

mesenchymal cells

connective tissue cell type that are stem cells

collagen, elastic, reticular

What are the three types of protein fibers?

collagen fibers

Large-diameter, rope-like fibers that provide tendons and ligaments with high tensile strength.

• Most Abundant

elastic fibers

Featuring bungee-cord like elasticity. Crucial for tissues that stretch and recoil.

• Skin & Blood Vessels

reticular fibers

Small-diameter fibers forming a delicate 3D scaffolding that holds cells in place.

• Spleen, Liver, Lymph

loose, dense

What two tissue types make up connective tissue proper?

loose connective

Type of connective tissue proper

Contains loosely packed fibers

• Areolar Tissue

• Adipose Tissue

• Reticular Tissue

dense connective

Type of connective tissue proper

Contains densely packed & more fibers

• ADense Regular CT

• BDense Irregular CT

• CElastic CT

areolar tissue

Loose connective tissue that consists of loosely-packed collagen, elastic and reticular fibers.

• Found in upper dermis of skin

• Also surrounds blood vessels

• When supporting epithelium it is sometimes known as lamina propria

adipose tissue

Loose connective tissue that consists of fat cells with little extracellular matrix

• Stores fat for energy and provides insulation

reticular tissue

Loose connective tissue made up of a network of reticular fibers that provides a supportive framework for soft organs such as the liver, spleen, and lymph nodes

dense regular connective tissue

• Consists of collagenous fibers packed into parallel bundles

• Gives tendons and ligaments their tensile strength

• Avascular

dense irregular connective tissue

• Consists of collagenous fibers interwoven into a mesh-like network.

• Found in lower dermis of skin and in submucosa layer of GI tract

elastic connective tissue

• Dense fibrous CT

• Consists of densely-packed elastic fibers

• Can stretch and recoil without damage

specialized connective tissue

Catch-all category for all connective tissues which don’t match the criteria for CT Proper