w3: tissue level of organisation

These flashcards cover key vocabulary and concepts related to the types of tissues in the human body, their functions, and their structural characteristics.

Tissue

A group of cells coming together to perform a specific function.

Epithelial Tissue

Tissue that lines external and internal structures, providing protection and allowing for absorption and secretion.

Connective Tissue

Tissue that connects, supports, and cushions structures throughout the body.

Muscle Tissue

Tissue responsible for movement, including skeletal, cardiac, and smooth muscle.

Nervous Tissue

Tissue involved in communication within the body via nerve signals.

Homeostasis

The maintenance of a stable internal environment in the body.

Basement Membrane

A thin, fibrous layer that anchors epithelial tissues to underlying connective tissues and acts as a semi-permeable filter.

Proliferation

The process of cell division and multiplication.

Differentiation

The process by which cells become specialized in structure and function.

Ectoderm

The outermost germ layer that develops into epidermis and nervous system.

Mesoderm

The middle germ layer that develops into muscles, bones, and connective tissues.

Endoderm

The innermost germ layer that develops into internal organs, such as the gut.

What is a germ layer?

A germ layer is a group of cells in an embryo that develops into specific tissues and organs in the body. There are three primary germ layers: ectoderm, mesoderm, and endoderm.

Apical Surface

The top surface of epithelial cells that tends to face outward, towards the environment or a lumen.

What is a lumen?

A lumen is the interior space of a tubular structure, such as blood vessels or the gastrointestinal tract, where substances can flow.

Basal Surface

The bottom surface of epithelial cells that sits on the basement membrane.

Avascular

Describes tissues that lack their own blood supply and rely on diffusion from underlying tissues for nutrients.

Intercellular

Referring to the space or connection between neighboring cells.

What characteristics does epithelial tissue have?

Basement membrane, highly cellular (dense packing with minimal intercellular substance), cellular polarity, apical surfaces face the exterior/interior lumen and is avascular.

Where can you find simple squamous epithelial tissue and what is their function?

Found in blood vessels, lungs, the lining of the heart, and lymphatic vessels. Allows materials to pass through by diffusion and filtration, and secretes a lubricating substance.

Where can you find simple cuboidal epithelial tissue and what is their function?

In glands, kidney tubules, and the ovarian surface. They are involved in the secretion and absorption of substances.

Where can you find simple columnar epithelial tissue and what is their function?

Bronchi, uterine tubes, uterus and smooth nonciliated tissue in the digestive tract (lining of stomach). They absorb and secrete mucous enzymes.

Where can you find pseudostatified columnar epithelial tissue and what is their function?

The lines of the trachea and the upper respiratory tract. They secrete mucus, and ciliated tissue moves the mucus, trapping particles and pathogens.

Where can you find stratified squamous epithelial tissue, and what is its function?

Found in the skin, mouth, and esophagus. It protects against abrasion.

Where can you find stratified cuboidal epithelial tissue, and what is its function?

Found in sweat glands, salivary glands, and mammary glands. It mainly functions in protection and secretion.

Where can you find stratified columnar epithelial tissue, and what is its function?

Found in the male urethra and some glands. It functions in protection and secretion.

Where can you find transitional epithelial tissue, and what is its function?

Found in the bladder, ureters, and urethra. It allows for stretch and contraction.

What are some characteristics of tight junctions?

Located apically, they eliminate intercellular space between neighbouring cell membranes to form a waterproof seal that forces all substances to pass through membrane receptors. Found in areas requiring strict control, such as the blood-brain barrier, stomach and bladder

What are some characteristics of adherens junctions?

Joining of actin filaments of adjacent cells to provide stability and support. They are found beneath tight junctions and help maintain tissue structure.

What are some characteristics of desmosomes?

Connect adjacent cells through cytoskeletal protein filaments, anchoring spots along neighbouring cell membranes that act like rivets locking cells together to resist stretching and tearing (mechanical forces); found in high-stress tissues such as skin and cardiac muscle.

What are some characteristics of hemidesmosomes?

Half a desmosome, connecting cells to the basement membrane instead of each other, located on basal surface and epidermis of the skin.

What characteristics do gap junctions have?

Aligned channel protein pores that connect adjacent cells, allowing cytoplasmic communication. They permit small molecules, nutrients and signalling molecules to pass. Allows sheets of cells to function in unison.

What are the three layers of skin?

Epidermis (stratafied squamous keratinised epithelium tissue - outer), Dermis (dense connective tissue - middle), Hypodermis (adipose tissue - inner).

What are the five layers of the Epidermis from outer to inner?

Stratum corneum, Stratum lucidum, Stratum granulosum, Stratum spinosum, Stratum basale.

What is the stratum corneum composed of?

multiple layers of dead, flat keratinised cells that have no nucleus.

What is the stratum lucidum composed of?

Made up of dead keratinocytes packed with eleidin (keratin), which are only found on the palms and soles of the feet.

What is the stratum granulosum composed of?

Keratinocytes that are flattening out and filling with keratin granules.

What is the stratum spinosum composed of?

Multiple layers of keratinocytes connected by desmosomes.

What is the stratum basal composed of?

The innermost layer, made up of a single row of cuboidal or columnar keratinocytes. Contains melanocytes and Merkel cells.

From innermost to outer most layer of epidermis?

Baby, Skin, Gets, Lots of Care. (Basal, spinosum, granulosum, lucidum, corneum)

What is a dominant fibre found in most dense connective tissue?

Collagen.

What function does an exocrine gland have?

Secretes substances through ducts.

What function does an endocrine gland have?

Secretes hormones into the extracellular space, transported by the bloodstream.

Exocrine gland can be either?

Unicellular or multicellular and secrete serous and/or mucous via apocrine, merocrine or holocrine.

Serous secretion is?

Thin watery, protein-rich fluid, such as digestive enzymes.

Mucous secretion is?

Think, viscous fluid for lubrication and protection.

A simple duct looks like? (multicellular only)

Tubular (straight), Coiled tubular (spiral), Branced tubular (multiple - straight), Alveolar/Acinar (bulb) or Branced Alveolar/Acinar (multiple - bulb)

A compound duct can be? (multicellular only)

Tubular (straight), Alveolar/Acinar (bulb), or Tubulovalveolar (both shapes combined).

What are some characteristics of keratinocytes?

They are the primary cell type in the epidermis, providing a protective waterproof barrier, and they produce keratin and lipid proteins to protect the skin.

What are some characteristics of Langerhans cells?

Derived from bone marrow, they ingest foreign antigens then migrate to the lymph nodes and warn the immune system.

What are some characteristics of Melanocytes?

Responsible for melanin production. Protect against UV and give skin colour.

What is a merkel cell?

A specialised cell type found in the epidermis that senses touch and pressure. Acts as a relay for sensory information to the nervous system. Concentrated in highly sensitive areas.

What is Apocrine?

When part of the cell itself is pinched off and released into the secretion, often seen in sweat glands.

What is merocrine?

Secreation via exocytosis.

What is Holocrine?

Secretion via cell rupture.

How are Cilia different from Microvilli?

Cilia moves substances across the cell surface while microvilli increase surface area for absorpiton.

What does Bone CT do?

Provides structural support, facilitates movement, houses bone marrow which produces blood cells.

What does Cartilage CT do?

Provides flexible support, reduces friction between bones, and absorbs shock.

What does dense regular CT do?

Found in tendons and ligaments, resists pulling forces in one direction

What does dense, irregular CT do?

Found in the dermis, provides strength/support, allowing flexibility in multiple directions.

What does Blood CT do?

Transports nutrients and waste throughout the body.

What does Adipose CT do?

Stores energy in the form of fat, provides insulation and cushions organs.

What are some types of loose connective tissue?

Adipose, areolar, reticular.

What is the extracellular matrix in connective tissues composed of?

Ground substance and fibres.

What is the dermis divided into?

Papillary dermis (loose CT, rich in cells and ground substance, nourishes the epidermis), and Reticular dermis (dense irregular CT that contains collagen fibres for strength and elasticity).

What is the Hypodermis?

The innermost layer of the skin that is primarily composed of adipose tissue.

What is a goblet cell?

A specialised epithelial cell that secretes mucus.

What is a fibroblasts cell?

The main CT responsible for producing and maintaining fibres, producing collagen and is the primary repair cell.

What are adipocytes?

Fat storage cells.

What are melanocytes?

pigment-producing cells, protect DNA and skin from UV damage

What are chondrocytes?

Cells found in cartilage that produce and maintain the cartilaginous matrix.

What are osteocytes?

Mature bone cells help maintain bone tissue and communicate with other bone cells to regulate bone health.

What do plasma cells do?

Produce anti-bodies.

What are Lymphocytes involved in?

White blood cells that identify and destroy pathogens.

Fibroblast =

fibre maker

Adipocyte =

Fat cel (adipose)

Melanocyte =

Melanin/pigment cell

Chrondrocyte =

Cartilage cell

Osteocyte =

Bone cell

Keratin is a?

Protein.

Reticulin?

A net-like mesh of thin fibres that forms a supportive scaffold within soft organs. (liver, spleen and bone marrow)

Elastin?

Protein that provides elasticity to tissues.

Collagen?

Most abundant CT tribe, forming thick strong bundles tat provide tensile strength and resistance to pulling forces. Primary fibre in rendons and ligaments.

What type of cell engulfs bacteria or cell debris within CT?

Macrophage.

Transitional epithelium is found?

In the lining of the bladder and urinary tract, allowing stretch and expansion.

What plays an important role in thermoregulation?

Sweat glands and blood vessels.

What component of CT is found between cells and fibres and is used for support and as a medium for chemical reactions?

Amorphous ground substance.

What type of junction stops materials from crossing the epithelial barrier?

Tight junction.

Another name for the subcutaneous layer is?

Hypodermis.

Anti-bodies are produced by?

Plasma cells.

Simple epithelia is associated with?

One layer, delicate, good for absorption, secretion, and filtration.

Stratified epithelia is associated with?

Multiple layers, tough, protection from stress.