Chapter 3: Cells and Tissues

Overview of Cells• Robert Hooke late 1600s

• Discovered cells through microscope• Human body made up of TRILLIONS of cells• Made up of four main elements and trace elements

• Four main:• Carbon, oxygen, hydrogen, nitrogen

• Trace: • Iron, sodium, potassium, iodine

• Cells are specialized and vary in form and function• We use a Generalized Cell model to study organelles

Anatomy of a Generalized Cell• Three main regions

• Nucleus• Cytoplasm• Plasma Membrane

Nucleus• Nuclear Envelope

(nuclear membrane)• Nuclear pores• Nucleoplasm

• Nucleoli• Sites where ribosomes

are assembled• Chromatin (DNA)

• During mitosis/meiosis, form chromosomes

Plasma Membrane

Membrane Junctions

Cytoplasm• Cellular material outside of the nucleus and inside the plasma

membrane• Contains ORGANELLES (little organs) and inclusions (stored

nutrients or cell products)

Organelles• Mitochondria:

• Double membrane – outer membrane and inner membrane (cristae)• Cellular respiration: Glucose ATP

• Ribosomes• Made of proteins and rRNA• Site of Protein Synthesis• Free and attached

• Endoplasmic Reticulum• Rough: studded with ribosomes. “Finishes” proteins made in

ribosomes• Smooth: cholesterol synthesis and breakdown, fat metabolism and

detoxification of drugs• Golgi Apparatus: modify package and sort proteins from the rough

ER. Secretory vesicles contain proteins and travel to the membrane.

Organelles Cont’d• Lysosomes: membrane “bags” containing digestive enzymes.

Cell’s demolition sites• Peroxisomes:

• Membranous sacs containing oxidase enzymes. Use O2 to detoxify harmful or poisonous substances (like alcohol)

• “Disarms” free radicals• Cytoskeleton: “bones and muscles” of cell. Made up of

microtubules, intermediate filaments, and microfilaments• Centrioles: rod-shaped bodies made up of microtubules which

help during mitosis. • Cilia and Flagella: used for movement

Cell Diversity• Some cell specialties: (From Fig 3.7 page 65)

• Cells that connect body parts• Fibroblast, RBCs

• Cells that cover and line body organs• Epithelial cell

• Cells that move organs and body parts• Skeletal, smooth muscle cells

• Cell that stores nutrients• Fat cell

• Cell that fights disease• Macrophage cell

• Cell that gathers information and controls body function• Neuron

• Cells of reproduction• Ovum, sperm

Cell Physiology:Membrane Transport• Solution:

• Made up of Solutes (what’s being DISSOLVED) and Solvents (the liquid the solute is added to)

• Intracellular fluid: nucleoplasm + cytosol. Contains small amounts of gases, nutrients and salts dissolved in water

• Interstitial fluid: rich, nutritious “soup” bathing the exterior of our cells

• Selectively permeable membrane: allows some substances through and not others

Passive Transport• Diffusion:

• Molecules move from an area of high concentration to low (DOWN the concentration gradient)

• Smaller molecules diffuse faster than larger ones• Simple diffusion through membrane• Osmosis – diffusion of water through membrane• Facilitated diffusion – protein carrier is used to “escort” large

molecules through the membrane• Filtration

• Water and solutes are forced through a membrane by hydrostatic pressure. Moves from high pressure area to low pressure area (down the pressure gradient)

• Used in kidneys

Active Transport• Movement of molecules

using ATP• Solute Pumping:

• Requires protein carrier (called solute pump) and ATP

• Transports amino acids, some sugars and most ions usually AGAINST concentration gradient

• Sodium-potassium pump• Na+ ions are moved out and

K+ are pumped into the cell

Active Transport Cont’d• Bulk Transport:

• Exocytosis:• Moves substances out of cell. Vesicles from Golgi apparatus fuses

with membrane and sends substances out.• Endocytosis

• Moves substances into the cell using membranous vesicles.• Phagocytosis: “Cell eating”. White blood cells ingest bacteria• Bulk-phase endocytosis (pinocytosis): “cell drinking”. Membrane

folds in and captures fluid containing solutes.

Cell Division• Cell Cycle has two phases:

Interphase (cell growth) and Cell Division

• Interphase:• Longest phase in the cell cycle.• Cell grows and prepares for division• Prepares by DNA Replication:

• DNA unwinds and makes two identical strands

• A-T, C-G

Cell Division• Mitosis

• Prophase: chromosomes form, nuclear envelope disappears• Metaphase: chromosomes align in center, spindles attach to

centromeres• Anaphase: chromatids separated by centrioles• Telophase: chromosomes uncoil, nuclear envelope forms

• Cytokinesis• Division of cytoplasm• Two daughter cells are formed

Mitosis

Protein Synthesis• DNA contains genes which code for proteins.• RNA

• mRNA: carries the “message” from the DNA to ribosome• tRNA: carries amino acids to ribosomes• rRNA: helps form ribosomes

• Transcription: transfer of information from DNA to complementary strand of mRNA. mRNA is written in triplet (codon). Each codon calls for a specific amino acid.

• Translation (protein synthesis): mRNA is “read” in the ribosome and tRNA brings the appropriate amino acid called for in the genetic code, matching anticodon to codon. Each amino acid is bonded together, forming a protein.

Transcription and Translation

Protein Synthesis

animation

Body Tissues: Epithelial• Epithelial tissue (epithelium) is the lining, covering, and

glandular tissue. Functions to protect, absorb, filter and secrete in the body.

• Simple and stratified• Epithelial cells

• Form continuous sheets• Have an apical surface• Rest on a basement membrane• Are avascular• Regenerate easily

Simple Epithelia• Simple squamous epithelium

• One layer on basement membrane• Air sacs in lungs, walls of capillaries, serous membranes

• Simple cuboidal epithelium• One layer of on a basement membrane• Glands and ducts, walls of kidney tubules, covers surface of ovaries

• Simple columnar epithelium• One tall layer• Goblet cells• Line digestive tract; mucosae

• Pseudostratified columnar epithelium• Some tall, some shorter cells• Absorption and secretion; goblet cells• Pseudostratified ciliated columnar epithelium lines respiratory tract

Stratified Epithelia• Stratified Squamous Epithelium

• Several layers of cells. Cells at free edge are squamous, near BM are cuboidal or columnar

• Esophagus, mouth, outer portion of skin• Stratified Cuboidal / Stratified Columnar Epithelium

• Two layers of cells. Surface cells are cuboidal/columnar• Rare; Ducts of large glands

• Transitional Epitheium• Basal layer are cuboidal or columnar; free surface cells vary• Highly modified. Found in urinary bladder, ureters and urethra

Glandular Epithelium• Endocrine

• Ductless. Secretions diffuse directly into blood vessels• Thyroid, adrenal, pituitary

• Exocrine• Ducts• Sweat, salivary, pancreas

Body Tissues: Connective• Bone

• Cells in lacunae surrounded by matrix of salt/collagen

• Cartilage• Hyaline cartilage (rubbery

matrix)• Larynx, breastbone, covers

bones in joints• Fibrocartilage

• Intervertebral discs• Elastic cartilage

• Supports external ear

Connective Tissue• Dense Connective Tissue

• Ligaments and tendons• Loose Connective Tissue

• Areolar tissue• Helps hold internal organs together; lamina propria; reservoir of

water and salts• Adipose tissue

• Fat; insulates body and protects organs• Reticular connective tissue

• Stroma in lymphoid organs

• Blood• Matrix = plasma.

Body Tissues - Muscle• Skeletal

• Voluntarily controlled; pull bones/skin to produce movement; long cells with multiple nuclei; striations

• Cardiac• Involuntarily controlled; found

in heart; uninucleate; form intercalated disks; striations

• Smooth• Involuntarily controlled; found

in digestive system, blood vessels, uterus, etc; no striations

← Skeletal

Cardiac →

← Smooth

Body Tissues - Nervous• Neurons and supporting

cells make up brain, spinal cord, and nerves

• Electrochemical impulses are transmitted. Irritability, conductivity

Tissue Repair• Regeneration

• Replacement of destroyed tissue by the same kind of cells• Fibrosis

• Repair by dense connective tissue. Forms scar tissue.• Injury Capillaries become permeable granulation tissue

forms surface epithelium regenerates

Developmental Aspects of Cells and Tissues• Tissues begin to break

down over time. “Aging”• Neoplasms – normal

control of cell division is bypassed and cells reproduce wildly

• Hyperplasia – tissues may enlarge because of an irritant or condition that stimulates the cells

• Atrophy – normal stimulation of a body area stops and the size of the body area decreases