Chapter 38 Flashcards
Which of the following sequences place the terms from simplest to more complex?
Cells, Tissues, Organs, Organ Systems, Human Body
Evolution of Multicellarity
-the transition begins with the evolution of cooperation, where cells unite together(b/c of environmental changes) and gain an advantage over solitary cells(predation)
Unicellular Organisms
-consists of only one cell that does everything
-Reproduce asexually(fragmentation, budding, and binary fission)
-More challenging for survival
-Interact directly with environment
Ex: Bacteria
Multicellularity
-Multiple different types of cells with different functions
-Macroscopic
-Most reproduce sexually
-Size of organism increases, as # of cells increase
-Don’t interact directly with environment to exchange materials
-Survival advantages
Levels of Organization in multicellular organism
Epithelial tissue, connective tissue, muscle tissue, and nervous tissue
Cell Theory
Humans contain 2 general classes of cells.
1. Somatic cells or body cells
2. Germ cells or reproductive cells: sperms and eggs
Tissues
-Made of cells that carry out a limited number of functions and they also form organs
-Formed by the same type of cells to act together in a function
Organ System
-functions share significant overlap
-Nervous system and endocrine system both operate via the shared organ, the hypothalamus
4 basic types of tissue
- Epithelial Tissue
- Connective Tissue
- Muscle Tissue
- Neural Tissue or Nervous Tissue
Epithelial Tissue
lines internal passageways and covers exposed external surfaces, forms glands(such as exocrine and endocrine
Connective Tissue
Fill internal free spaces, transports materials like blood within the body, stores energy like triglycerides, and form supportive framework
Muscle Tissue
Specialized in contraction, produce movement
Neural Tissue or Nervous Tissue
Generate and conducts nervous impulses
Junctions of various kinds link cells into tissues
- Tight Junctions
- Anchoring Junctions
- Gap Junctions
Tight Junctions
Plasma membrane proteins of adjacent cells interact to fuse the two cells partly together and thus create a barrier between cells(tissue lining the urinary bladder prevent waste molecules/ions from leaking out of the bladder into other body tissues
Anchoring Junctions
Form button like spots or belts that weld cells together(most abundant in tissues subject to stretching like skin and heart muscle)
Gap Junctions
Open direct channels between cells in the same tissue(cardiac cells help heart contract in unison)
Epithelium Tissue(epithelia)
-Covers body surfaces(skin)
-Lines body cavity and tubular structures
-Function: Form barriers between body’s internal and external environment and different fluid compartments in body
Certain epithelia(such as those lining the stomach, intestine, and secretory glands) are able to
-Transport materials into the internal environment from outside(absorption)
-Transport materials from the internal environment to the outside(secretion)
Epithelium Tissue Characteristics
-Highly cellular(exclusively made of cells)
-Highly polar(structural and functional differences b/w exposed and attached surfaces
-Avascular(lack blood vessels)
-Attached to basement membrane or basal lamina
-Ability to regenerate(damages epithelial cells can be replaced by the division of epithelial stem cells)
Epithelial tissue functions
-Protect internal environment from abrasion and invasion of microorganisms
-Mediate exchange or materials(gases, ions, etc) b/w internal and external environments
-Absorption or secretion(produce glands(sweat, etc))
General Structure of Epithelium: Barrier
-adjacent cells are joined by tight junctions that limit the passage of material through the spaces b/w cells(paracellular spaces)
-permit fluids on either side of cell layer to differ in composition
-Tight junctions important in maintaining homeostasis
-“tightness” of these junctions varies from location to location; tight epithelia have junctions with extremely low permeabilities, whereas leaky epithelia have junctions that are more permeable
General Structure of an Epithelium: Absorption
-for absorption, cells that make up the epithelial tissue must transport substances inward across the membrane on one side of cell and outward across membrane on opp. side of cell.
-must possess different transport systems
-b/c membranes on the two sides are distinctly different(in both structure and function), epithelial cells are said to be polarized
Classification of Epithelia Based on Cell Shape
- Squamous(flat)
- Cuboidal(box-like)
- Columnar(elongated)
Squamous(flat)
-Scalelike, flat, thin, irregular shape
Cuboidal(box-like)
-Cubelike, hexagonal boxes, nucleus round/circular located almost centrally
Columnar(elongated)
Column-shaped, nucleus elongated located basally
Classification of Epithelia: Number of Cell Layers
1.Simple
2. Stratified
Simple Epithelia
Single layer of cells
Stratified Epithelia(Multilayered)
2 or more layers of cells
Polarity of Epithelial Tissue
-Apical Surface: Exposed to outside environment or fluid in body
-Basal Surface: Basal lamina or basement membrane. Anchors epithelia to the connective tissue
Simple Squamous epithelium
-layer of flattened cells
-Locations: Blood vessel inner lining(endothelium) and air sacs of lungs
-Function:Diffusion
Stratified Squamous epithelium
-Several layers of flattened cells
-Locations: Skin and other surfaces subject to abrasion such as the mouth, esophagus, and the vagina
Function:Protection against abrasion; usually not subject to secretion and absorption
Cuboidal epithelium
-Layer of tubelike cells; free surface may have microvilli
-Locations: Glands(sweat, etc) and tubular parts of nephrons in kidneys
-Function: secretion and absorption
Simple columnar epithelium
-Layer of tall, slender cells with nuclei near base. Free surface may have cilia or microvilli; may contain secretory vesicles
-Locations:Lining of gut, cervical canal and gallbladder
-Function:Secretion, absorption, such as secreting digestive enzymes and absorbing nutrients in the gut; protection; secreting mucus
Simple pseudo(false)stratified columnar epithelium
-Single layer of columnar cells of differing heights; some cells do not reach the apical surface. b/c of this, nuclei are staggered.
-Locations:Nasal Cavities, trachea, and upper digestive tract; some parts of male reproductive system
-Function: Protection, secretes mucus and moves it across surface
Stratified Columnar epithelium
-Locations: Small areas of the pharynx, epiglottis, anus, mammary glands, and salivary gland ducts, and urethra
-Function: Protection
Transitional Epithelium
-Locations: Urinary bladder; renal pelvis; ureters
-Functions: Permits repeated cycles of
stretching without damage
