Anatomy I - Epithelial Tissue and Integument Flashcards
Epithelial Tissue and Integument
Hierarchy of Body Structure (Organization of Animals)
- Cells – smallest functional, living (basic) units
- Tissues – structurally similar cells; their product(s) grouped together to perform a common function
- Organ – specialized structure consisting of two or more different tissues
- Organ System – an aggregate consisting of at least two organs for a common functional purpose
- Organism – the summation of the organ systems
Composition (Components) of All Tissues
- Cells
- Cell Products = Intercellular Substance – all the ‘stuff’ between the cells
a. Fibers – formed elements… threadlike
b. Ground Substance – amorphous… background material
Four Basic Tissues of the Human Body
- Epithelial Tissue
- Connective Tissue
- Muscle Tissue
- Nervous Tissue
Membrane Epithelium Characteristics
a. Highly cellular with very little intercellular substance
b. Free surface faces (exposed to) air or fluid (inside of air passages, GI tract, blood vessels, etc.)
c. Basal surface is attached to a basement membrane, which separates it from the vascular
connective tissue layer deep to it
d. Avascular – dependent upon diffusion for survival
e. Surface cells often have specializations
Membrane Epithelium Functions
a. Protection – from mechanical trauma, abrasion, desiccation, bacteria
b. Transport – of fluids through (or “across”) the membrane
c. Secretion – releasing glandular products
d. Absorption – taking of materials into the cell
e. Excretion/Lubrication – releasing cell wastes… sweat(ing), oil, etc.
Number of cell layers
1) Simple – one layer of cells
2) Stratified – more than one layer of cells
Cell shape
1) Squamous – flat cell
2) Cuboidal – cell are about as tall as they are wide – not truly cuboidal when seen three
dimensionally
3) Columnar – taller than they are wide
Simple Squamous Epithelium Locations
a. Endothelium – lining of blood vessels
b. Bowman’s capsule – kidney
c. Thin segments of the loop of Henle – kidney
d. Alveoli of lungs
Simple Squamous Epithelium Functions
a. Transport
b. Diffusion
Simple Cuboidal Epithelium Locations
a. Lining of several of the tubules of the kidney
b. Ovary
c. Lining of many ducts of glands
Simple Cuboidal Epithelium Functions
a. Secretion
b. Transport
c. Absorption
Simple Columnar Epithelium Locations
a. Lining of GI tract
b. Lining of uterus
c. Lining of oviduct
Simple Columnar Epithelium Functions
a. Protection
b. Lubrication
c. Absorption
d. Secretion
Pseudostratified (ciliated) Columnar Epithelium
appears stratified when looking at a histological section though
this is false; every cell is attached to the basement membrane but not all cells have a free surface
Pseudostratified (ciliated) Columnar Epithelium Locations
respiratory tract
Pseudostratified (ciliated) Columnar Epithelium Functions
a. Protection
b. Secretion
Stratified Squamous Epithelium
several layers of cells with the cells of the free surface being flattened
Keratinized stratified squamous epithelium
the surface cells are dead cells filled with keratin
Dry
Keratinized stratified squamous epithelium Locations
1) Skin
2) Gingiva
3) Hard palate
Keratinized stratified squamous epithelium Functions
mainly protection from abrasion, desiccation, UV light
Non-keratinized stratified squamous epithelium
Moist
Non-keratinized stratified squamous epithelium Locations
1) Mouth
2) Esophagus
3) Vagina
Non-keratinized stratified squamous epithelium Functions
mainly protection against abrasion
Stratified Cuboidal Epithelium
sweat glands
Stratified Columnar Epithelium
found in conjunctiva
Transitional Epithelium
the surface cell is very large and “transitional”… sometimes flat, square, or tall
Transitional Epithelium Locations
urinary system
Transitional Epithelium Functions
stretchy and protective of the underlying connective tissue
Epithelial Cell Free Surface
Microvilli
Cilia
Cilia
a. Structure – large, motile projections from the surface of the cell – has a specific structure of
microtubules
b. Location – free surface of respiratory tract and oviduct
c. Function – move materials along free surface
Microvilli
a. Structure – delicate fingerlike projections from the cell surface
b. Location – free surface of intestinal cells
c. Function – increase surface area to increase the efficiency of absorption from the gut
Epithelial Cell Lateral Surface
Junctional complex Gap Junction (Macula Communicans)
Gap Junction (Macula Communicans)
provides communication between the cells (in the heart it allows
action potentials to jump from one cell to the next)
Junctional complex
forms a continuous “girdle” around the lateral surfaces of the cell near the free
surface – a complex with 3 parts
a. Tight Junction (Zonula Occludens) – the upper most component of the junctional complex -
occludes the extracellular space and therefore acts to prevent solutes from passing through the
extracellular space between epithelial cells (“C” on the diagram below)
b. Zonula Adherens – not as “tight” with some extracellular space present (“D” below)
c. Desmosomes (Macula Adherens) – spot junction - like a ‘dab’ of glue – does not continue
around the entire cell, just in spots
Basal Surface – the “bottom”
- Basement membrane – a semipermeable barrier between the epithelium and its underlying connective
tissue – it’s formed by both the epithelium and connective tissue - Hemidesmosomes – attach the cells to the basement membrane
Secretion
the process of making a specific product in the gland which is released for use elsewhere
Excretion
elimination of wastes
Origin of Glands
most derive from the epithelium
Exocrine glands
a. Secretes products through a duct to an external (skin) or internal (stomach, intestines) surface
b. Examples: Salivary glands, Sweat glands, Pancreas, Liver, Goblet Cells, GI tract glands,
Sebaceous glands, Mammary glands
Endocrine Glands
a. Secretes products into the blood
b. Examples:
Pituitary gland
Pineal gland
Thyroid gland
Thymus
Adrenal glands
Ovaries
Testes
Islets of Langerhans (Pancreas
Coverings of the Body
A. Skin 1. Epidermis 2. Dermis B. Superficial Fascia/Subcutaneous layer/Hypodermis C. Deep Investing Fascia
The Integumentary System
A. Functions – essential to life
1. Protection – from drying, light, bacteria, minor abrasions
2. Excretion – sweat
3. Secretion – sebaceous glands
4. Sensation – tests the environment: pain and touch receptors in epidermis, touch and pressure
receptors in the dermis and hypodermis
5. Storage – fat
6. Synthesis – keratin, melanin, vitamin D
7. Temperature regulation – evaporation of sweat, insulation of fat, blood supply changes in response to
temperature
The Integumentary System
B. Integument Proper – Skin
1. Epidermis – the outer layers of skin, 0.07 to 0.12 mm thick; keratinocytes are dominant cell type
keratinized stratified squamous epithelium; avascular; contains some pain and touch sensory receptors
a. Stratum Basale (Stratum Germinativum) – deepest layer of low cuboidal cells; supported by the
basement membrane; layer where mitosis (which occurs at night) mostly occurs; cells then
differentiate, forming the subsequent outer layers until finally being sloughed off the free
surface; Merkel cells and melanocytes also in this layer
e. Stratum Corneum – most superficial layer; keratinized part of this epithelium; varies in
thickness; dead cells continually slough off as they reach the free surface; cells are filled with
keratin which was in the granules of the stratum granulosum
Dermis
connective tissue component of skin that lies immediately deep to the epidermis; 0.6 to 3 mm
thick (thicker in men than in women); consists of mostly Type I collagen and a network of elastic fibers;
connects epidermis to underlying hypodermis; forms two indistinct layers
Papillary Layer
superficial layer forming papillae (projections) that stick up into the
epidermis; usually loosely woven connective tissue consisting of predominantly Type
III collagen and elastic fibers; contains numerous fibroblasts, macrophages, plasma
cells, mast cells, etc.; many capillary loops – role in maintenance of body temperature;
contains numerous nerve endings, e.g. mechanoreceptors, temperature receptors,
and pain receptors
Reticular Layer
consists mostly of Type I collagen and some elastic fibers densely
but irregular arranged, predominantly parallel to the surface of the skin; contains the
epidermal appendages, e.g., hair follicles, sweat glands, and sebaceous glands; cells
are sparser than in above lying papillary layer but some fat cells are now present;
contains encapsulated mechanoreceptors
Langer’s Lines
Under the microscope the collagen fibers appear to have an irregular pattern,
but three dimensionally there is a parallel pattern to them. If you get a cut that goes across
these lines (which indicate the directions of collagen fibers) then the collagen fibers retract a
little and leave a gaping wound. If the cut runs parallel to these lines then the collagen fibers
tend to pull the two sides of the wound together and they heal more effectively.
Hypodermis: aka Superficial Fascia or Subcutaneous Layer
a. Adipose connective tissue
b. Distribution (how much is located in which part of the body) varies depending on sex, climate
and diet
c. NAVL - Lots! - Deep pressure sensory receptors abundant
Nonkeratinocytes of the epidermis
a. Langerhans cells: aka Dendritic cells
b. Melanocytes
Langerhans cells: aka Dendritic cells
1) Mostly found in the stratum spinosum
2) Originate from bone marrow precursor cells and are part of the mononuclear
phagocyte system
3) Function in the immune response as antigen-presenting cells
Melanocytes
1) Mostly found in the stratum basale; vary in number depending upon location of skin of
the body
2) Derived from neural crest cells; numbers amazingly similar amongst the various races
3) Large cells with numerous processes that interdigitate amongst the keratinocytes
4) Synthesize melanin
Derivatives of the Skin
- Sweat glands: aka Eccrine glands
- Apocrine sweat glands
- Sebaceous glands
- Nails - compacted stratum corneum
- Hair – Arrector pili muscles
Hair – Arrector pili muscles
smooth muscles that attach to the hair sheath. When they contract, the
hair stands up instead of lying down. They respond to fear, cold and anger.
Sebaceous glands
a. Found throughout the skin of the body except on the palms/soles of the hands and feet
b. Secrete sebum – an oily, wax-like mixture of cholesterol and triglycerides
c. Opens into the hair follicle canals; maintain skin texture and hair flexibility
d. Secrete in response to sex hormones
e. Obstruction of duct results in acne
Apocrine sweat glands
a. Larger than Eccrine sweat glands and found only in certain areas of the body
1) Axilla (armpit)
2) Areola of nipple
3) Anal region
b. Opens into the canals of the hair follicles
c. Secretion under the influence of hormones; doesn’t begin to secrete until puberty; secrete sex
attractants in lower animals
d. Innervated by the sympathetic nervous system
Sweat glands: aka Eccrine glands
a. Number from 3 to 4 million and found al over the body
b. Important for thermoregulation of body temperature
c. Simple, coiled tubular merocrine gland that opens at a sweat pore
d. Innervated by the sympathetic nervous system
Cutaneous sensory receptors
- Merkel’s receptor
- Meissner’s corpuscle
- Pacinian corpuscle
- Ruffini’s ending
- Free nerve ending
- Hair receptor
