LEx1 Review

To review for Final Exam

Homeostasis

The maintenance of relatively stable internal conditions (chemical and physical) despite continuous changes in the external environment

Components of Homeostatic Control

Requires a receptor (detects change), a control center (receives input and determines response), and an effector organ (provides the response)

What are the characteristics of epithelial tissue?

Cellularity, polarity, attachment, avascularity

Simple squamous

Single layer of flat cells; specialized for quick exchange by diffusion and filtration

Simple cuboidal

Single layer of cube-shaped cells; typically metabolically active in secretion and absorption (e.g., glands, kidney tubules)

Simple columnar

Consisting of a single layer of tall cells, often containing goblet cells or cilia; Its main functions are absorption and the secretion of mucus, enzymes, and other substances (e.g., uterine tubes, small bronchi)

Stratified squamous

Multiple layers with flattened apical cells; major function is protection in areas subject to abrasion (e.g., skin, oral cavity)

Stratified cuboidal

Rare, typically consisting of only two layers, found in glands and provide protection

Stratified columnar

Rare and features columnar cells only in its uppermost layer, found in the pharyngeal and male urethra, for protection

Pseudostratifed columnar

This tissue is a single layer at differing heights, when ciliated, it lines the respiratory tract and functions in absorption, secretion, and the propulsion of mucus

Transitional epithelium

Specialized stratified tissue lining urinary organs (e.g., bladder); cells change shape to accommodate stretching and filling (change shape from rounded/bulbous (when empty) to flattened/elongated (when distended), thereby permitting organ stretching and expansion)

Microvilli

Cellular projections containing microfilaments (actin); function to increase surface area for absorption (e.g., digestive tract brush border)

Cellularity

Cells fit closely together, often forming sheets held by junctions like tight junctions and desmosomes

Polarity

They have distinct Apical (top) and Basal (bottom) surfaces. The apical surface may bear microvilli or cilia

Attachment

The basal surface rests on an acellular Basement Membrane (BM)

How do epithelial tissues get nutrients if they are avascular?

Underlying vascularized Connective Tissue (CT) offers nourishment via diffusion

Sagittal

Divides the body into left and right parts

Midsagittal (Median)

Divides into equal left and right parts. Note: A single sagittal section cannot pass through both lungs

Frontal (coronal)

Divides into anterior and posterior parts

Transverse

Divides into superior and inferior parts

Ipsilateral

same side

Contralateral

opposite side

Dorsal cavity

Cranial and spinal cavities

What is the dorsal cavity surrounded by?

meninges

Ventral cavity

Thoracic and abdominopelvic cavities

What are the ventral cavities separated by?

diaphragm

Thoracic cavity

Upper part of ventral cavity: Contains lungs and the heart

What is the lungs surrounded by?

pleura

What is the heart surrounded by?

pericardium

Abdominopelvic cavity

Includes abdominal and pelvic cavities, physically combined

What are the abdominal and pelvic cavities surrounded by?

peritoneum

Cutaneous membrane composition

Keratinized stratified squamous epithelium + thick layer of CT (dermis)

Cutaneous membrane characteristics

Forms the skin, it’s a dry membrane, superficial cells are dead and contain keratin

Cutaneous membrane function

Protection/Boundary

Mucosa membrane composition

Epithelia sheets + areolar CT

Mucosa membrane characteristics

Lines body cavities and passageways open to the exterior, and it is a moist membrane bathed by secretions (or urine)

Mucosa membrane function

Secretion and absorption

Mucosa membrane examples

Digestive, respiratory, urogenital tracts

Serous membrane composition

Simple squamous epithelium resting on thin areolar CT

Serous membrane characteristics

Lines body cavities close to the exterior, and it is a moist membrane

Serous functions

Secretes lubricating fluid to reduce friction between moving organs and helps isolate infections

Serous membrane examples

Pleurae, pericardium, peritoneum

Serosa Layers composition

Parietal serosa (outer balloon wall) that lines the cavity wall, and visceral serosa (inner balloon wall) that covers the organ

Serosa Layer characteristics

It’s the space between the layers containing lubricating fluid

Serosa Layer function

Reduces friction caused by organ movement

CT membranes composition

Synovial membranes and meninges

Synovial membrane

lining joint capsules

Meninges

surrounding the central nervous system: brain and spinal cord

CT membranes function

Support and cushioning

Nucleus

Control center of the cell

Mitochondria

produces energy

Rough ER

Associated with ribosomes; make secretory and membrane proteins

Smooth ER

Makes lipids

Golgi Apparatus

modifies and packages proteins

Hyperplasia

Cell growth by increase in cell number (via mitosis/proliferation)

Hypertrophy

Cell growth by increase in volume

Multicellular organisms originate from a single _______ cell.

totipotent

Totipotent cell

SC that has the ability to develop into any cell type in the body

What does differentiation depend on?

Differential gene expression and environmental cues

As cells differentiate, they lose what ability?

proliferation

Cytoskeleton

Provides internal framework

Microfilaments (Actin)

found in microvilli to increase surface area for absorption

Intermediate Filament

Ropelike fibers resisting pulling forces (e.g., Keratin), attached to desmosomes

Microtubules

Hollow tubes forming cilia/flagella for movement, used as cellular transport highways

Tight junctions

impermeable junctions that form leak-proof sheets, separating apical from basolateral regions, and creating a physicochemical barrier

Desmosomes

Anchoring junctions that distribute mechanical stress via intermediate filaments

Gap junctions

Channels allowing direct chemical communication between cells, coordinating functions

Hemidesmosomes

Anchor cells to the basement membrane

Hydrophilic

Capable of dissolving freely in water but not in oil (polar)

Hydrophobic

Lipophilic; repelled by water

Salts (electrolytes)

Conduct electrical currents; vital for membrane potential energy (Na+, K+, Cl-, Ca2+)

Glucose

Hydrophilic, polar, essential for energy

Passive transport

Does not need ATP → molecules move down their concentration gradient. Includes simple and facilitated diffusion, and osmosis

Simple diffusion

Movement of particles from high to low concentration across the membrane without a transporter (Ex. small, uncharged molecules like O2 and CO2)

Faciliated Diffusion

Movement that requires a protein transporter (channel or carrier). Ions move down their existing concentration gradient. The transport rate is limited by the number of transporters available (saturation).

Osmosis

movement of water across a selectively permeable membrane. Water flows down its gradient (from low to high solute concentration) and is often facilitated by aquaporins.

Active transport

requires metabolic energy (ATP) to move solutes against their concentration gradient (flow up gradients)

Primary Active Transports

Uses direct metabolic energy (ATP). Pumps solutes up their concentration gradient.

Why is primary active transport necessary?

To create the concentration gradient that stores electrochemical potential energy for secondary transport. This process can occur only in the plasma membrane of a living cell.

Primary active transport example

Na+/K+ ATPase pump

Secondary Active Transport

Uses stored potential energy from primary transport gradients to move one molecule down its gradient, powering another against its gradient.

Secondary active transport example

Sodium-glucose cotransporter (derived from Na+ concentration gradient)

What are specialized transporters and channels?

Uniporter, symporter, antiporter, leakage channels, ligand-gated and voltage-gated channels

Uniporter

Transports a single molecule across the membrane. Often passive, down gradient

Symporter

Transports two molecules simultaneously in the same direction. One solute down its gradient and another up its gradient (secondary active transport)

Antiporter

Transports two molecules simultaneously in opposite directions; Secondary active transport

Leakage channels

Ion channels that open randomly to allow ions to flow down their established concentration gradient; Passive facilitated diffusion

Ligand-Gated Channel

Opens only when a signaling molecule (ligand, e.g., Acetylcholine) binds the transporter; Passive facilitated diffusion

Voltage-gated channel

Opens or closes in response to changes in the membrane potential; passive facilitated diffusion

Bulk Transport examples

endocytosis and exocytosis

Endocytosis

Processes for importing substances into the cell; phagocytosis and pinocytosis

Exocytosis

Processes for exporting substances out of the cell via vesicle fusion; neural signaling and merocrine secretion

Phagocytosis

“cell eating”; engulfs large solid particles like bacteria

Pinocytosis

“cell drinking”; engulfs extracellular fluid and dissolved solutes

Fluid compartments

ICF = 2/3 (67%), ECF = 1/3 and ISF = ¾ (25%), IVF = ¼ (8%)

What is the healthy ion distribution of fluid compartments?

High Na+ in ECF, high K+ in ICF. ECF is positively charged; ICF is negatively charged

Osmolarilty

determines the solution's tonicity and the direction of water movement across a semipermeable membrane

Tonicity

Refers to a solution's ability to cause a cell to shrink or swell due to water movement

At equilibrium, what is the tonicity of ICF and ECF?

ICF is always isotonic to ECF

Hypotonic

Characteristic of a solution outside the cell (lower solute concentration in ECF) that causes water to flow into the cell (swell)