Chapter 4 Tissue Flashcards
Tissue
Collection of specialized cells that perform limited number of functions
Histology
the study of tissues
Four main types of tissue
- Epithelial tissue (covering, surfaces, linings, glands)
- Connective tissue (support fill space, structure, strength, transport, storage
- Muscle tissue ( movement)
- Nervous tissue (Control, transmit info)
Primary Germ layers
embryonic layers, give rise to all four tissue types in adult
Epithelial Tissue (2 categories)
- Epithelia- covering
- Glands- produce fluid secretions
Features of Epithelial Tissue
- Cellularity: little extracellular matrix mostly cells
- Contacts: cells linked by strong junctions
- Polarity: apical + basal surfaces, separate functions
- Attachment: attached to CT via basal lamina
- Avascularity: diffusion from CT
- Regeneration: high turnover, stem cells at basal surface
Functions of epithelial tissue
- Provide Physical protection
- Control permeability
- Provide sensation
- Produce specialized secretions
Structure of Epithelial tissue
- Apical Surface: exposed to environment may have: microvilli: absorption or secretion
cilia: fluid movement - Basolateral Surface: attachment to neighboring cells via intercellular connections
Basal lamina ( a.k.a basement membrane)
- Lamina lucida: from epithelia
glycoproteins + fine filaments
restrict large molecule movement - Lamina densa: from CT
coarse protein fibers
provide strength
Squamous
flat, disc shaped nucleus
Cuboidal
Cube, center round nucleus
Columnar
tall, basal oval nucleus
simple
one cell layer
stratified
2 or more protection
Simple squamous epithelium
-thin, delicate
-in protected regions
-Locations:
-mesothelium
(serosa)
-endothelium
(blood vessels, heart)
-kidney tubules
-conjunctiva
-alveoli of lungs
-Functions:
absorption, diffusion, filtration or secretion
Stratified Squamous Epithelium
-basal cells look cuboidal, apical cells
squamous
-on exposed surfaces
-two types:
A. Nonkeratinized = mucosa
-kept moist
-all cells nucleated
Locations:
-mouth, esophagus
-anus
-vagina
B. Keratinized = epidermis
-dry, apical cells dead
-cells contain keratin protein
to resist dehydration
-Functions:
provide protection from abrasion,
pathogens, chemicals
Simple Cubodial Epithelium
-Locations:
-kidney tubules
-pancreas
-salivary glands
-thyroid
-Functions:
-secretion or absorption
Transitional Epithelium
-relaxed: looks like stratified cuboidal
-stretched: looks squamous
-Locations:
-urinary bladder
-ureters
-Function:
-tolerate excessive stretching
Simple Columnar Epithelium
-nuclei line up near basal lamina
-apical surface of cells often has microvilli =
“brush border” (in intestine)
-goblet cells often present: secrete mucus
-Locations:
-stomach
-intestine
-gallbladder
-uterine tubes
-collecting ducts of kidney
-Functions:
-absorption or secretion
Pseudostratified Columnar Epithelium
-several cell types:
varying shapes and functions
-all cells contact basal lamina
-some too short to reach apical surface
-nuclei scattered so it appears stratified
-tall cells have cilia on apical surface
-goblet cells (mucus) often present
-Locations:
-nasal cavity, trachea, bronchi
-male reproductive tract
-female uterine tubes
-Functions:
-move material across surface
Stratified Columnar Epithelium
-rare
-two layers or multiple layers with only
apical layer columnar
-Locations (tiny parts of):
-pharynx, epiglottis
-anus
-mammary glands
-salivary glands
-urethra
-Functions
-minor protection
Glandular Epithelium
for secretion makes up glands
Endocrine glands
“internally secreting” secrete into interstitial flood, blood secretions= hormones
Exocrine Glands
“externally secreting”
secrete into duct, epithelial surface
e.g. digestive enzymes, perspiration,
tears, milk, mucus
Classified three ways:
a. mode of secretion
b. type of secretion
c. structure
Modes of secretion
- Merocrine secretion
- Apocrine secretion
- Holocrine secretion
Merocrine secretion
-product released from
secretory vesicles
by exocytosis
e.g. mucus, sweat
Apocrine secretion
-product accumulates in vesicles
-apical region of cell with vesicles is shed
to release product
e.g. milk
Holocrine secretion
product accumulates in vesicles
-whole cell is lysed to release product
-cell dies, must be replaced by stem cells
e.g. sebum
Type of secretion
- Serous glands: water + enzymes
e.g. parotid salivary gland - Mucus glands: mucin
(+water = mucus)
e.g. goblet cell - Mixed exocrine glands:
serous + mucus secretion
e.g. submandibular salivary gland
Gland Structure
- Unicellular Gland: 1 cell e.g goblet cell
- Multicellular gland: group of cells named for shape and structure
Connective Tissue (CT) features
-never exposed to environment
-usually vascularized
-consists of cells in matrix
Components of
