epithelial tissue Flashcards
What is the function of epithelial tissue?
protect, absorb, secrete, excrete
Where is the epithelial tissue located?
On the surface of the body/covering the lining of allow organs/composes glands
What are the distinguishing features of epithelial tissue?
- lack blood supply (avascular)
- cells readily divide
- Cells are tightly packed
How are epithelial tissue typically organized?
- Apical surface exposed to free space
- lack a matrix
- has a thin extracellular layer named the “basement membrane” - basal membrane. That connects it to connective tissue
How does epithelial tissue get its nutrients?
thru diffusion from other surrounding tissue
What are the major types of epithelial tissue?
- squamous (thin, flattened cells)
- Cuboidal (cube shaped cells)
- Columnar (elongated cells)
What is simple epithelial tissue?
Epithelial tissue is classified as simple when all of the cells reach the bottom (Basal) membrane, and the free apical surface. They only have ONE layer.
What is stratified epithelial tissue?
- Epithelial tissue is stratified when it is composed of two or more layers on cells. Only one layers reaches the bottom, and only one layer reaches the top.
- Useful for protection/ composition of glands
What are the general characteristics of epithelial tissue?
- covers the external body surface (skin) and hollow organs/cavities
- Protects, secretes, absorbs, excretes
- Has an apical surface that faces a free space
- Has no blood supply
- Has little to no matrix
- Composes glands
- Typical packed together to form a barrier as protection
- Cells divide easily in order to heal injuries (skin)
General characteristics of a simple squamous cell
- Is common in sites of diffusion/filtration because the lining is typically very thin and is therefore more permeable
- Lines air sacs such as alveoli/capillaries
- Lines blood/lymphatic vessels
- Thin/delicate and are injured easily
General characteristics of a simply cuboidal cell
- Single layer of cube shaped cells
- Most cells have centrally located, spherical nuclei
- Lines the kidney tubules/thyroid follicles/covers ovaries/lines ducts of some glands
- In the tubules/ducts the free surface typically faces the hollow channel or LUMEN.
- In kidneys it aids in the production of urine
- In glands it helps secrete glandular substances
WHAT IS LUMEN?!
A HOLLOW CHANNEL OMG
General characteristics of ciliated columnar cells
- Single layer of elongated cells that are taller than they are wide
- Nuclei usually @ the same level, near the basement (basal) part of the membrane
- In ciliated cells the cilia are on the free surface and are constantly moving (aids in helping move the oocytes in female reproductive cells thru urine tube to the uterus)
General characteristics of conciliated columnar cells
- lines the uterus/ small portions of the digestive track such as the small/large intestines
- The tissue is thick and protects the underlying tissue
- Secretes digestive fluids and absorbs nutrients
- Simple non-ciliated columnar cells are specialized in absorption usually have microvilli on their free surface
- Microvilli extends the free surface to absorb more nutrients
What are goblet cells?
Goblet cells are scattered thru columnar cells and secrete mucus on the free surface on the tissue
What is a pseudo-stratified columnar cell?
- These cells appear stratified but aren’t.
- The nuclei are on different levels
- Often have cilia/goblet cells
- Protect from infection
- Lines the respiratory passage ways
What are the general characteristics of a stratified squamous cell?
- Cells are thick and used for protection
- The outermost cells are flattened whilst the bottom layers tend to either be columnar or cuboidal
What’s the functions/locations of squamous cells?
- Typically make up the epidermis
- As older cells are pushed outward they gather protein called “keratin” and become “keratinized”
- Keratinized cells harden and dry out which makes it harder for microorganisms to get thru/serves as a protective layer
Located: in the oral, vaginal, anal cavities. These surface cells don’t die and remain moist
General characteristics of stratified cuboidal epithelium
- consists of two or more layers of cube-shaped cells that line the hollow channel of the lumen
- Lines the mammary, sweat, salivary glands and the pancreas
- Offers more protection
- Also lines some reproductive organs in both male/females
