Functionally related groups of cells that work together
Types of tissues
Epithelial
Connective
Muscle
Nervous
Epithelial tissue
Covers a body surface or lines a body cavity
Forms most glands
Functions: Protection, Absorption & Secretion, Filtration, Forms slippery surfaces
Epithelial tissue characteristics
Cellularity - cells in close contact with little intercellular space
Specialized contacts - junctions for attachment and communication
Polarity - apical and basal surface
Support by connective tissue - contributes to basement membrane
Avascular - nutrients must diffuse
Innervated
High capacity for regeneration
Lateral surface features of epithelial cells
Adhesion proteins link plasma membranes of adjacent cells
Special cell junctions: Tight junctions, Gap junctions, Desmosomes
Tight junctions
Close off intercellular space, prevent molecules passing between cells
Desmosomes
Two disc-like plaques connected across intercellular space, proteins interdigitate into extracellular space, intermediate filaments insert into plaques
Gap junctions
Passageway between two adjacent cells, let small molecules move directly between neighboring cells
Simple epithelium
One layer of cells
Stratified epithelium
More than one layer of cells
Squamous epithelium
Cells wider than tall, plate or "scale" like
Cuboidal epithelium
Cells as wide as tall, cube-like
Columnar epithelium
Cells taller than wide, column-like
Pseudostratified columnar epithelium
All cells originate at basement membrane, only tall cells reach apical surface, nuclei at varying heights
Simple squamous epithelium
Single layer of flat cells with disc-shaped nuclei
Functions: Passage of materials by diffusion and filtration, Secretes lubricating substances
Locations: Renal corpuscles, Alveoli of lungs, Lining of heart, blood and lymphatic vessels, Lining of ventral body cavity
Simple cuboidal epithelium
Single layer of cube-like cells with large, spherical central nuclei
Functions: Secretion and absorption
Locations: Kidney tubules, Secretory portions of small glands, Ovary & thyroid follicles
Simple columnar epithelium
Single layer of column-shaped (rectangular) cells with oval nuclei
Some bear cilia at apical surface, May contain goblet cells
Functions: Absorption, Secretion of mucus, enzymes, and other substances, Ciliated type propels mucus or reproductive cells
Locations: Non-ciliated - Lines digestive tract, gallbladder, ducts of some glands, Ciliated - Lines small bronchi, uterine tubes, uterus
Pseudostratified columnar epithelium
All cells originate at basement membrane, only tall cells reach apical surface, may contain goblet cells and bear cilia, nuclei at varying heights
Functions: Secretion of mucus, propulsion of mucus by cilia
Locations: Non-ciliated - Ducts of male reproductive tubes, Ducts of large glands, Ciliated - Lines trachea and most of upper respiratory tract
Stratified epithelia
Contain two or more layers of cells, Regenerate from below, Major role is protection
Stratified squamous epithelium
Many layers of cells, squamous in shape at apical layer, deeper layers cuboidal or columnar
Keratinized - Surface cells dead and full of keratin, Non-keratinized - Moist lining of body openings
Functions: Protects underlying tissues in areas subject to abrasion
Ducts carry products of exocrine glands to epithelial surface, May be unicellular or multicellular
Goblet cells
Produce mucin, Mucin + water = mucus, Protects and lubricates many internal body surfaces
Multicellular exocrine glands
Classified by structure of duct and mode/type of secretion (merocrine, apocrine, holocrine)
Connective tissue
Most diverse and abundant tissue, Main classes: Connective tissue proper, Blood, Cartilage, Bone, Components: Cells, Matrix (protein fibers, ground substance), Common embryonic origin - mesenchyme
Functions: Voluntary movement, Manipulation of environment, Facial expression
Locations: Skeletal muscles attached to bones
Smooth muscle tissue
Spindle-shaped cells with central nuclei, Arranged in sheets, No striations
Functions: Propels substances along internal passageways, Involuntary control
Locations: Mostly walls of hollow organs
Cardiac muscle tissue
Branching cells, Uni-nucleate, Intercalated discs
Function: Contracts to propel blood into circulatory system
Location: Walls of heart
Nervous tissue
Transmits electrical signals from sensory receptors to effectors, Main components: Brain, spinal cord, nerves, Contains neurons and supporting neuroglial cells
Rectum
The last part of the colon that stores feces until defecation
Anal sphincter
Controls defecation
Appendix
A vestigial attachment of the cecum
Located between the small and large intestine
Summary of Digestive Enzymes
Salivary amylase
Pepsin (protease)
Trypsin (protease)
Lipase
Nuclease
Salivary amylase
Breaks down starch
Pepsin
Breaks down proteins
Trypsin
Breaks down polypeptides into peptides
Lipase
Breaks down fats into fatty acids and glycerol
Nuclease
Breaks down nucleic acids into nucleotides
pH
Optimal pH for each enzyme
The presence of large numbers of mitochondria in the cells lining the small intestine allows them to absorb nutrients