EPHE 141 Epithelial Tissue & Connective Tissue Proper

embryonic origin of tissue types

• Ectoderm produces the nervous tissue and all associated organs as well as some epithelial tissues.

• Mesoderm produces muscular tissues, connective tissues, and some epithelial tissues.

• Endoderm produces epithelial tissues

define histology

study of the microscopic anatomy of cells and tissues

main functions of epithelial tissue

protection, diffusion, filtration, absorption, and secretion, transportation

anatomical organization (5)

cells → tissues → organs → organ systems → organism

characteristics of living things (4)

energy production/consumption, growth/repair, adaptation, reproduction

where is epithelial tissue found

external body surfaces, lining body cavities and hollow organs, form glands, ducts

How do the different shapes of epithelial cells contribute to their function?

Their shape is optimized for their function- thinner/flatter cells (squamous) will be better at diffusion, while thicker/taller cells (columnar) will be better for protection against harsher environments.

Structure & function of the basement membrane

Structure = two layers:

1. Basal lamina (ep. cells adhere to)

2. Reticular lamina (reticular connective tissue)

Function = providing support to the ET and binds it to other structures.

what shape of epithelial cells has cilia, an how does that relate to its function in the body?

Cilia are found only on pseudostratified columnar epithelial cells. These cells are found in the respiratory tract and the sperm duct. In he cilia functions to trap and transport dust and unwanted particles away.

why is it so common for cancer to occur in epithelial tissue? What are ET cancers called?

because epithelial tissue regenerates quickly, there is more opportunity for mutations to happen in mitosis. These cancers are called carcinomas.

where is transitional epithelia found and how does its shape optimize its function?

transitional epithelia is found in the bladder (urinary tract). It looks like jumbled cells closer to the BM, but at the surface cells appear to be cuboidal in a relaxed position. This is to allow for stretch in the epithelial tissue (into more of a squamous shape) as the bladder expands.

Simple squamous ET: structure, function, location

• Structure: single layer of flat cells

• Function: diffusion, filtration, absorption, secretion, reducing friction

• Location: alveoli, endothelium (blood vessels)

what is the simple squamous ET called when it is found in blood vessels?

endothelium

Stratified squamous ET: structure, function, location

• Structure: many layers of flat cells

• Function: protection

• Location: epidermis, oral cavity, nasal cavity

Difference in structure, function and location of keratinized and non-keratinized stratified squamous epithelium

Keratinized stratified squamous ET is more resistant to abrasion due to the presence of keratin protein that makes the cells water resistant.

Keratinized: epidermis, hair, nails

Non-“ “: mouth, nose, etc.

What does “polarity” mean when referring to epithelial tissue?

Sidedness- the apical surface faces away from the BM, or towards the lumen/external environment. The basolateral surface interacts with other epithelial cells and the basement membrane. This is necessary for selective movement of substances in/out/through the tissue.

Simple cuboidal ET specialization and locations

Specialization: secretion and absorption

Location: ducts and glands (kidney, ovary, thyroid, etc.)

Simple columnar ET specialization and locations

Specialization: absorption and secretion

Location: digestive and respiratory linings

Simple columnar and cuboidal ET both have the same specialization but are found in different areas. Why?

Columnar cells are thicker, so they are better suited for the harsh environment of the digestive tract

stratified cuboidal/columnar ET specialization and location

Specialization: secretion

Location: (limited)

• Cuboidal: sweat/mammary glands

• Columnar: pharynx, male urethra, some glands

what are the main differences between exocrine and endocrine glands?

• endocrine glands are generally ductless, and exocrine glands usually have ducts

• endocrine glands release hormones directly into nearby capillaries via exocytosis

• exocrine glands secrete directly onto the epithelial surface

what type of epithelial tissue performs exocrine and endocrine functions?

glandular epithelia

what are the two ways that glandular epithelia is classified?

1. Uni or multicellular

2. Method of Secretion (apocrine, merocrine, holocrine)

Explain each method of secretion for glandular epithelia and give an example of each in the body

• Apocrine: pinches off top part of cell, taking some of the cell membrane with it. Example: some sweat glands (armpit, groin), mammary glands

• Merocrine: secretion via exocytosis. Example: most sweat glands, salivary glands

• Holocrine: cell bursts, resulting in cell death. Example: sebaceous glands

list the three main categories of connective tissue and the two subcategories from each

• CT Proper: Loose, Dense

• Supporting CT: Cartilage, Bone

• Fluid CT: Blood, Lymph

Give all tissue types within Loose CT

Areolar, adipose, reticular

Give all tissue types within Dense CT

Dense regular, dense irregular, elastic

Give all tissue types for Cartilage

Hyaline, elastic, fibrous

Give all tissue types for Bone

compact, spongy

list main functions of CT

Protects internal structures

• Structural framework for organs

• Stores energy

• Insulation

• Transports fluid and solutes

• Assists the immune system

What components do all types of connective tissue have?

1. Specialized cells

2. Extracellular protein fibres

3. Ground substance

What types of EC protein fibres are found in CT proper? What property do each contribute to the kinds of tissues they are found in?

• Collagen: strong, unbranched

• Reticulin: collagen subtype, forms a mesh-like network, strong, lighter than collagen

• Elastic: thin, branching, stretch and recoil

What are the specialized cells found in CT Proper?

Fibrocytes/fibroblasts, adipocytes, immune cells

Example of a unicellular exocrine gland

goblet cell

Difference between simple and compound multicellular exocrine glands

Simple multicellular exocrine glands have an unbranched duct, and multicelllular “ " have a branched duct

What are the different shapes of multicellular exocrine glands

• Alveolar: more spherical at the end, like alveoli in the lung

• Tubular: tube-like structure

• Tubuloalveolar: elements of alveolar and tubular

what is mesenchyme?

mesenchyme are the undifferentiated cells that differentiate and form most connective tissues in the body. It originates from the embryonic mesoderm.

what are the similarities and differences in meaning between the suffixes “-cyte” and “-blast”, and at least one example in CT.

• Both refer to an immature, not fully differentiated cell

• “-cyte”: refers to a cell that typically lives in the tissue to support it

• “-blast”: refers to a cell that makes/remodels a tissue, secreting ground substance in the early stage of tissue formation

• Eg:

  1. fibroblast vs fibrocyte, both specialized cells found in CT Proper

  2. osteoblast vs osteocyte, both specialized cells found in Supportive CT (bone)

  3. chondroblast vs chondrocyte, both specialized cells found in Supportive CT (cartilage)

what are macrophages?

Macrophages are specialized immune cells found in CT Proper, that function to engulf pathogens and debris via phagocytosis.

There are two types:

• Resident (fixed) macrophages: live in the tissue

• Wandering (free) macrophages: in the bloodstream

Function of adipocytes in CT Proper

thermoregulation, insulation, energy storage, protection

Ground substance:

• What is ECM?

• Main components and function in CT Proper

• Ground substance and protein fibres

• Interstitial Fluid: composed of water, macromolecules, hormones, neurotransmitters, etc.

• Cell adhesion proteins: bind cells to the ECM (aka Cell Adhesion Molecules, or CAMs)

• Proteoglycans: assemble into complexes that trap water in the ECM

• high concentration of glycosaminoglycans, which hydrate the tissue (eg: hyaluronic acid)

Function of fibroblasts in CT Proper

Synthesize the ECM, produce protein fibers, play a role in immune response

Areolar tissue: type of connective tissue, composition, function, locations in the body

• Loose CT within CT Proper

• Composition: loosely packed, all types of protein fibers (collagen, reticular, elastic), gel-like ground substance

• Function: cushions organs, support while allowing movement, defense via immune cells, delivers nutrients and removes wastes

• Locations: beneath epidermis (papillary layer), surrounding organs

Adipose tissue: type of connective tissue, composition, function, locations in the body

• Loose CT within CT Proper

• Composition: primarily composed of adipocytes, less visible ground substance, lipid droplets (triglycerides) found within adipocytes behave similarly to the areolar matrix. Very similar do areolar tissue with the exception of the amount of adipocytes.

• Function: energy, cushioning, protecting major organs

• Locations: around major organs, under dermis

Reticular tissue: type of connective tissue, composition, function, locations in the body

• Loose CT within CT Proper

• Composition: lots of reticular fibers. Reticular cells produce/are woven into reticular fibers, that form a strong and flexible mesh-like structure

• Function: multidirectional strength, supporting the functions of the lymph nodes, bone marrow, etc. where it is found

• Locations: lymph nodes, bone marrow, liver, kidney, spleen

Dense reg tissue: type of connective tissue, composition, function, locations in the body

• Dense CT within CT Proper

• Composition: ordered assembly of collagen fibers, some elastin, poorly vascularized because of the tightly packed fibers→ difficult to heal

• Function: resisting pulling forces

• Locations: muscle to bone (tendon) or bone to bone (ligament), aponeurosis

Dense irregular tissue: type of connective tissue, composition, function, locations in the body

• Dense CT within CT Proper

• Composition: collagen in an irregular pattern, some elastin, poorly vascularized due to amount of protein fibers → difficult to heal

• Function: multi-directional strength

• Locations: dermis, joint capsules, and coverings of organs and body cavities

Elastic tissue: type of connective tissue, composition, function, locations in the body

• Dense CT within CT Proper

• Composition: ordered arrangement of mostly elastic fibers, some collagen

• Function: stretch & recoil

• Locations: relatively rare, some ligaments, artery walls

what are general characteristics of epithelial tissue

• Avascular

• Regenerative\

• Attachment (to BM)

• Polarity (sidedness)

• cellularity (tightly packed)

what is endothelium?

simple squamous epithelial tissue found in the blood vessels