Chapter 3: Cells and Tissues

1. Chapter 3: Cells and Tissues

2. 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

3. Anatomy of a Generalized Cell • Three main regions • Nucleus • Cytoplasm • Plasma Membrane

4. Nucleus • Nuclear Envelope (nuclear membrane) • Nuclear pores • Nucleoplasm • Nucleoli • Sites where ribosomes are assembled • Chromatin (DNA) • During mitosis/meiosis, form chromosomes

5. Plasma Membrane

6. Membrane Junctions

7. Cytoplasm • Cellular material outside of the nucleus and inside the plasma membrane • Contains ORGANELLES (little organs) and inclusions (stored nutrients or cell products)

8. 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.

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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 cellusing membranous vesicles. • Phagocytosis: “Cell eating”. White blood cells ingest bacteria • Bulk-phase endocytosis (pinocytosis): “cell drinking”. Membrane folds in and captures fluid containing solutes.

15. 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

16. 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

17. Mitosis

18. 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.

19. Transcription and Translation

20. Protein Synthesis animation

21. 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

22. 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

24. 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

26. Glandular Epithelium • Endocrine • Ductless. Secretions diffuse directly into blood vessels • Thyroid, adrenal, pituitary • Exocrine • Ducts • Sweat, salivary, pancreas

27. 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

28. 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.

29. 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

30. Body Tissues - Nervous • Neurons and supporting cells make up brain, spinal cord, and nerves • Electrochemical impulses are transmitted. Irritability, conductivity

31. 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

32. 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