Histology Flashcards
Eukaryote definition:
Any cell or organism that possesses a clearly defined nucleus
What is the role of the plasmalemma and what does it consist of?
Separates cytoplasm from outside environment, forming a selectively permeable barrier.
Can exocytose and endocytose material.
Consists of:
- Phospholipid bilayer
- Integral proteins
What is the cytosol?
Solution of proteins, electrolytes and carbohydrates which the cellular components are embedded
What is the structure of the nuclear envelope (3)?
Has an inner and outer nuclear membrane with the perinuclear cistern in the middle
Outer nuclear membrane is studded with ribosomes
Has nuclear pores that allow the transport of molecules across the nuclear envelope
Euchromatin and heterochromatin definitions:
Euchromatin: DNA is more dispersed and undergoing transcription
Heterochromatin: DNA highly condensed and not undergoing transcription
Where are different RNAs synthesised?
mRNA and tRNA synthesised in nucleus
rRNA synthesised in nucleolus
Where are ribosomes formed and how do they function?
Formed in nucleolus
Small subunit of ribosome binds RNA, large subunit of ribosomes catalyzes peptide bond formation
Role of RER:
Studded with ribosomes making it responsible for protein synthesis and initiation of glycoprotein formation
Role of SER:
Involved in continuous processing of proteins from RER and lipid synthesis
Structure and role of Golgi apparatus:
Composed of a group of flattened, membrane bound cisternae
Transport vesicles arrive at Golgi from SER; Golgi modifies and packages them
What is the role of the cytoskeleton and what are the 3 main protein filaments?
Consits of protein filaments which allow movement of organelles and also movement of the cell itself
Microfilaments
Intermediate filaments
Microtubules
Structure, function and features of the 3 main protein filaments:
Microfilaments: composed of actin, involved in cellular movement, cytokinesis, endo and exocytosis etc., 7nm
Intermediate filaments: 6 proteins that bind intracellular elements together and to the plasmalemma, >10nm
Microtubules: composed of ⍺ and β tubulin, originate from centrosome, polar, dynein and kinesin attach and move along them, 25nm
What are the 3 modes of cellular transport and how do they work?
Endocytosis: membrane invaginates, fuses, newly made endocytic vesicle buds into cell, often receptor mediated.
Exocytosis: works in reverse to endocytosis
Phagocytosis: bacteria engulfed and digested
What are occluding junctions:
Intracellular junctions that link cells to form a diffusion barrier
Also known as tight junctions or zonula occludens
Function of anchoring junctions and the 3 types:
Provide mechanical strength
Adherent junctions: link submembrane actin bundles of adjacent cells via cadherin molecules
Desmosomes: link submembrane intermediate filaments of adjacent cells
Hemidesmosomes: link submembrane intermediate filaments of cells to extacellular matrix through transmembrane proteins
What are Communicating junctions (gap junctions)?
Intracellular junctions that allow movement of molecules between cells
Each junction is a circular patch studded with pores
What do haemotoxylin and eosin do?
Haematoxylin stains acidic molecules purple
Eosin stains basic molecules pink
Structure of epithelium:
Cover surfaces of the body, lines hollow organs, forms glands
Backed by a basal lamina (basement membrane)
Non-vascular
What is the basal lamina?
A thin layer of specialised extracellular material between the basal surface of epithelial cells and the underlying tissue
Apical and basal definitions:
Apical: faces the lumen of a tube or the external environment
Basal: attaches to the basement membrane
Functions of epithelium:
- Mechanical barrier
- Chemical barrier
- Absorption
- Secretion
- Containment
- Locomotion
Pseudostratified definition:
Multiple layers, all in contact with basal lamina
Cell/tissue surface specialisations:
- Microvilli
- Cilia
- Keratinized
Endocrine and exocrine glands function:
Endocrine: Product secreted towards basal end of cell and distributed by vascular system - ductless
Exocrine: Product secreted towards apical end of cell - ducted
Soft connective tissue:
Make up tendons and ligaments
Loose: loosely packed fibres separated by ground substance
Dense: densely packed bundles of collagen fibres
Dense soft connective tissue; regular and irregular:
Dense regular: fibres aligned
Dense irregular: fibre bundles run in many directions
What are features hard connective tissue and what does it make up?
Strong, flexible, compressible, semi-rigid.
Makes up:
- 3 types of cartilage - hyaline, elastic, fibrocartilage
- Bone
Bone structure:
Outer shell of cortical bone makes up shaft - diaphysis
Cancellous/trabecular bone occupies ends - epiphyses
What are examples of fluid connective tissue?
Blood and lymph.
What is force in muscle contraction?
Movement of actin fibres over myosin fibres
3 main types of muscle and their features:
Smooth muscle: involuntary, non-striated, single nucleus
Skeletal muscle: voluntary, striated, multinucleated
Cardiac: involuntary, striated, single nucleus in centre, has intercalated discs that contain many intracellular junctions for stability
Nervous tissue connective tissue coat in CNS and PNS:
- Meninges in CNS
- Epineurium in PNS
3 types of glia in CNS and their function:
Astrocytes: provide support, involved in ion transport
Oligodendrocytes: produce myelin
Microglia: immune surveillance
Glia of PNS and its function:
Schwann cells: produce myelin and supports axons
3 layers of mucosa:
Endothelium (inner): sits on basal lamina
Lamina propria (middle): loose connective tissue
Muscularis mucosae (outer): thin layer of smooth muscle
4 major layers of GI tract:
Mucosa
Submucosa: Made of loose connective tissue
Muscularis externa: 2 thick layers of thick muscle (inner circular layer and outer longitudinal layer)
Serosa or adventitia: Outer layer of connective tissue
What is the difference between serosa and and adventitia?
Serosa suspends digestive tract
Adventitia attaches to other organs
What is protective mucosa and where is it found?
Non-keratinized stratified squamous epithelium
Found in:
- Oral cavity
- Pharynx
- Oesophagus
- Anal canal
What is absorptive mucosa and where is it found?
Simple columnar epithelium with villi and tubular glands
Found in small intestine
What is secretory mucosa and where is it found?
Simple columnar epithelium with extensive tubular glands
Found in stomach
What is protective and absorptive mucosa and where is it found?
Simple columnar epithelium with tubular glands
Found in large intestine
What is the nervous system of the GI tract?
ENS
3 main components of the respiratory system:
Bronchi: large diameter airways, hyaline cartilage in their wall
Bronchioles: small diameter airways, no cartilage, mainly smooth muscle
Alveoli: site of gas exchange, lined by simple squamous epithelium
What are hepatic lobules?
Small divisions of the liver defined at the histological scale
Exocrine and endocrine glands:
Exocrine: Secrete pancreatic digestive enzymes
Endocrine: Islets of Langerhans → cause secretion of insulin and glucagon
Components of blood:
erythrocytes (RBCs) ~45%
buffy coat (leukocytes and platelets) <1%
plasma ~55%
Where are clotting factors found?
In plasma
What is serum?
Solution remaining after removal of clotting factors
Features of erythrocytes (RBCs)
Biconcave discs around 7µm in diameter
No nucleus or organelles (when mature)
Form a network of flexible cytoskeletal elements
Features of neutrophils:
- 40-75% of WBCs
- Phagocytes (when activated)
- Single, multi-lobed nucleus
Features of eosinophils:
- 5% of WBCs
- Acidic granules that stain red, and a bi-lobed nucleus
- Granules contain hydrolytic enzymes - inflammation
Features of basophils:
- 5% of WBCs
- Basic granules that stain purple/blue, and a bi-lobed nucleus
- Effector cells in allergic reactions
Features of monocytes
- 1-5% of WBCs
- Precursors of tissue macrophages (phagocytes)
- Large, kidney bean-shaped nucleus
Features of lymphocytes:
- 20-50% of WBCs
- Small spherical nucleus and basophilic (blue) cytoplasm
Which blood cell plays a key role in homeostasis?
Platelets
Structure of arteries:
Tunica intima: Single layer of squamous epithelial cells supported by a basal lamina and a thin layer of connective tissue
Tunica media: Predominantly made up of smooth muscle
Tunica adventitia: Made up of supporting connective tissue
Structure of arterioles:
1 or 2 layers of smooth muscle in tunica media, almost no adventitia
3 types of capillary:
Continuous: no pores
Fenestrated: small pores
Discontinuous: large gaps
Structure of venules and postcapillary venules
Postcapillary venules: Endothelium and thin layer of connective tissue
Venules: Intermittent smooth muscle in tunica media
Difference in vein structure:
Has a thinner, continuous, tunica media
Types of neurones:
Multipolar: Many dendrites, one axon
Bipolar: One dendrite, one axon
Pseudounipolar: Axon in both directions due to short process
