Tissues Flashcards
What is a zygote?
fusion of a sperm and ovum
What is a blastomere?
identical cells formed by cleavage divisions
What is a morula?
solid mass of blastomeres surrounded by zona pellucida, usually reaches uterus 4 days after fertilization
When does the morula reach uterus?
4 days after fertilization
What is a blastocyst?
hollow ball that forms when the morula contains exactly 32 cells
When is the blastocyst composed of hundreds of cells?
By the end of the 5th day
What are the two type of cell types in the blastocyst stage?
Trophoblast and inner cell mass
What is a microvilli?
fingerlike extensions of the plasma membrane that increase the exposed surface area.
What are cilia?
tiny hairlike projections that propel substances along their free surface
What are basal lamina?
noncellular adhesive, thin supporting sheet that is adjacent to basal surface of epithelium and consists of glycoproteins secreted by epithelial cells * selective filter and scaffolding that epithelial cells migrate along to repair a wound
What is the reticular lamina?
layer of extracellular material containing network of collagen protein
What is a trophoblast?
single layer of flattened cells
What is an inner cell mass?
small cluster of 20-30 cells
What are the 4 stages of formation of primary germ layer?
cleavage, blastocyst, implantation and gastrulation
When does a blastomere form a solid mass called morula that forms a hollow ball called blastocyst?
when there are exactly 32 cells
What happens during implantation?
Trophoblast cells secrete enzymes, which break down the zona pellucida and allow blastocyst to “hatch” at approx. day7. Blastocyst floats in uterine cavity until day 7-8, when it adheres to endometrium (lining of uterus) and embeds in uterine wall
What is timeline of events for formation of germ layer?
Day 4: ovum in upper uterine tube
Day 7: blastocyst hatches
Day7-8: floats in cavity
and then adheres to uterine wall
What are the stages by day?
Day 4: blastomere -> morula
Day 7: blastocyst
Day 7-8: blastocyst
What are the two trophoblast layers?
cellular trophoblast and syncytiotrophoblast(inner and outer layer, respectively)
How long does implantation take?
one week and finishes by day 14
What is hCG?
Human chorionic gonadotropin, which is secreted by trophoblast cells during implantation and later secreted by chorion. where placenta ultimately takes over endocrine function
HELPS MAINTAIN UTERINE LINING
what happens to inner cell mass during implantation?
becomes bilaminar embryonic disc to develop into embryo proper and separation in epiblast becomes amniotic cavity
What happens during gastrulation?
after amnion forms, embryonic disc elongates and primitive streak appears on dorsal surface and bilaminar embryonic disc transforms into three-layered embryo
What are the three primary germ layers?
endoderm, ectoderm and mesoderm
Endoderm, ectoderm and mesoderm is common where?
epithelia (endoderm) Nervous system(ectoderm) Everywhere else (mesoderm)
What is histology?
study of tissues
What are the four types of tissues and their functions?
Epithelial (lining for digestive tract, respiratory system, urogenital system, glands in these systems)
Connective (provides structural support)
Muscle (able to perform contraction and cause movement to occur)
Nervous (electrical impulses)
3 GENERAL FEATURES THAT HELP TO ANCHOR CELLS AND STABILIZE TISSUES
Glycoproteins on cell surface
Basement membranes
intercellular junctions
What are the types of junctions?
Tight, adherens, desmosomes, hemidesmosomes and gap
what are the functions of tight junctions?
result from fusing together of transmembrane proteins of adjacent cells; tight to eliminate space to make materials impermeable to movement in cell layer
what are functions of adherens junctions?
dense protein layer at inner surface of plasma membrane
(a plaque) attaches to membrane proteins and cytoskeletal proteins
Transmembrane glycoproteins, called cadherins, attach intracellularly to a plaque - extend through plasma membrane and attach intracellularly to a plaque - extend through plasma membrane and attach to cadherins from an adjacent cell
Cadherins are one type of cellular adhesion molecule (CAM)
Adhesion belts (areas of extensive adherens junctions) are often present in epithelial tissues
Most common in epithelial tissues
Identify the stages of pre-embryonic development, beginning at fertilization at gastrulation. Describe the main event(s) of each stage.
Cleavage: zygote begins to divide 24 hrs after fertilization and continues with the more rapid mitotic divisions of cleavage as it travels down the uterine tube. Period of fairly rapid mitotic divisions of zygote without intervening growth.
36 hrs after fert., first cleavage division created two identical cells called blastomeres
72 hrs post fert., morula forms: loose collection of cells that form a berry-shaped cluster of 16+ cells and travels toward uterus
Blastocyst Formation: fluid-filled hollow sphere composed of single layer of large, flattened cells called trophoblast cells and inner cell mass
Day 4/5 post fert., 100-cell embryo floats in uterus
Zona pellucida breaks down and blastocyst hatches from it
Trophoblast cells: single layer of flattened cells
Inner cell mass: small cluster of 20-30 rounded cells clinging to inside of blastocyst
Creates placenta to protect against mother’s cells from attack
Describe the histological differences between a morula and a blastocyst.
A morula is a loose collection of cells that from a berry-shaped cluster of 16 or more cells and the blastocyst contains both trophoblast cells and a small cluster of 20-30 rounded cells called the inner cell mass surrounded by the zona pellucida
What are the two distinct cellular components of a blastocyst?
Trophoblast: single layer of flattened cells
Inner cell mass: small cluster of 20-30 rounded cells clinging to inside of blastocyst
What is the function of a trophoblast?
Adheres to endometrium (lining of the uterus) and embeds in uterine wall to proliferate and form two distinct layers
What role does human chorionic gonadotropin (hCG) play in sustaining pregnancy? How has knowledge of this hormone become clinically and commercially useful?
The trophoblast cells secrete hCG to maintain the viability of the corpus luteum. It bypasses hypothalamic-pituitary-ovarian controls at this critical time and prompts the corpus luteum to continue secreting progesterone and estrogens. It also has protease activity and is an autocrine growth factor that promotes placental development.
From what embryonic structure does the bilaminar embryonic disk originate?
develops into the embryo proper from inner cell mass
Identify the three primary germ layers and describe which tissues ultimately derive from each.
Endoderm -> the epithelial linings of the digestive, respiratory and urogenital systems, and the glands associated with these systems
Ectoderm -> the structures of the nervous system and the skin epidermis
Mesoderm -> virtually everything else
Identify the four extraembryonic membranes and describe the function of each.
mucous membranes – line cavities which open to the outside of the body (e.g., respiratory & digestive tracts)
composed of epithelium (may be simple or stratified) over a thicker layer of loose CT (called the lamina propria)
serous membranes –
moist membranes that line body cavities that do not open to the outside, and that cover organs in that cavity
composed of simple squamous ET which lies on top of subserous fascia
serous membranes consist of 2 layers:
parietal layer lines body cavity
parietal layer reflects back over the organs in the cavity to form the visceral layer
serous fluid is secreted into the potential space between the visceral & parietal layers
cutaneous membrane –usually referred to as “the skin”
synovial membranes –line joint cavities of freely moveable (synovial) joints
What is a tissue?
A tissue is a group of cells that are similar in structure and perform a common or related function. Four primary tissue types interweave to make the body: epithelial, connective, muscle and nervous
Identify and describe the general function of each of the four basic tissue types.
Epithelial tissue covers
Connective tissue supports
Muscle produces movement
Nervous tissue controls
What three general features tend to anchor cells together and stabilize tissues?
Glycoproteins on cell surface
Basement membranes
Intercellular junctions
Describe the structure and function of each of the five common types of cellular junction
Tight junctions – result from fusing together of transmembrane proteins of adjacent cells
Adherens junctions –
Dense protein layer at inner surface of plasma membrane (a plaque) attaches to membrane proteins and cytoskeletal proteins
Transmembrane glycoproteins, called cadherins, attach intracellularly to a plaque –extend through plasma membrane and attach intracellularly to a plaque - extend through plasma membrane and attach to cadherins from an adjacent cell
Cadherins are one type of cellular adhesion molecule (CAM)
Adhesion belts (areas of extensive adherens junctions) are often present in epithelial tissues
Desmosomes –
Similar to adherens junctions
Additionally, have intermediate filaments attached to inner surface of plaque – extend through cytoplasm and attach to desmosome on opposite side of cell
Hemidesmosomes –
Hemidesmosome plaque:
Has transmembrane integrin proteins inserted
Integrins attached to laminins on outside of cell
Intermediate filaments attach to plaque on cytoplasmic face
Anchor cells to basement membrane
Gap junctions –
Adjacent cells are close together
There are fuses transmembrane proteins in the plasma membrane hollow cylinders called connexons
Connexons of adjacent cells connect in the intercellular spaces to form gap junctions
Allows passage of chemical substances between cells
Identify the two major categories of epithelial tissue.
Covering and lining epithelium - forms the outer layer of the skin; dips into and lines the open cavities of the urogenital, digestive, and respiratory systems; and covers the walls and organs of the closed ventral body cavity
Glandular epithelium - fashions the glands of the body
What special characteristics of epithelial tissue distinguish it from other tissue types?
polarity
Specialized contacts
Supported by connective tissues
Ability to regenerate
What type(s) of specialized lateral contacts are common in epithelium?
Lateral contacts like tight junctions and desmosomes that bind adjacent cells together at many points to form continuous sheets
What is meant when we describe epithelial tissue as demonstrating polarity?
It simply means that the apical surface and basal surface differ in both structure and function, which is why we assume there is polarity. ET cells exhibit polarity, simply means that the cells near the apical surface are different than the ones nearer the basal surface
What is the function of the basement membrane?
Reinforces the epithelial sheet, helps it resist stretching and tearing, and defines epithelial boundary
Identify the two layers of the basement membrane and describe their positions relative to the surrounding epithelium and connective tissue.
Basal lamina - lamina lucida, thin layer secreted by ET cells, acts as selective filter between blood and ET
Reticular lamina - lamina densa, deeper layer made up of network of collagen fibers produced by underlying CT
Which layer of the basement membrane is produced by epithelial cells? By fibroblasts in the connective tissue?
The basal lamina is the layer secreted by ET cells and reticular lamina is the layer made up of fibroblasts in CT
What are the general functions of covering and lining epithelium?
Primary function is protection
Controls permeability - thus, helps regulate materials that enter/leave body
Surface transport
Sensory functions
Distinguish among the different kinds of epithelia tissue according to cell shape and number of cell layers present.
Number of cell layers present Simple - single layer of cells Stratified - two or more layers of cells Pseudostratified - cells falsely appear to be stratified, but only one layer is present Cell shape - height of cells in apical layer of ET Squamous - thin and flattened Cuboidal - cube shaped Columnar - long and narrow
What are the primary functions of simple epithelium? Of stratified epithelium?
Simple epithelia - single cell layer found where absorption, secretion and filtration occur and thin epithelial barrier is desirable
Stratified epithelia - two or more cell layers stacked on top of each other are common in high abrasion areas where protection is important, such as the skin surface and lining of mouth, Primary function protection
What is a gland?
Consists of one or more ET cells specialized to produce and secrete a product called a secretion
Distinguish between endocrine and exocrine glands.
Endocrine - secrete hormones directly into interstitial fluid surrounding the secreting cell
Exocrine - secrete their products into ducts
Identify, locate, and describe the function of the human body’s only unicellular exocrine gland.
mucous cells and goblet cells. Simple column- secrete mucin (a glycoprotein that dissolves in H2O to produce mucus in epithelial linings of intestinal and respiratory tracts amid columnar cells
What are the two basic structural components of multicellular exocrine glands?
Epithelium derived duct and secretory unit (acinus) consisting of secretory cells
What is the difference between simple and compound exocrine glands?
Simple - unbranched duct
Compound - branched duct
What is the difference between the tubular, alveolar, and tubuloalveolar secretory portions of multicellular exocrine glands?
Tubular - secretory cells form tubes
Alveolar - if secretory cells form small, flask-like sacs
Tubuloalveolar - both types of secretory units
Name the three functional types of exocrine gland and describe the secretory process of each.
Merocrine - secrete products by exocytosis as they are produced/sweat and salivary
Holocrine - accumulate products until they rupture/sebaceous oil glands. Dies after.
Apocrine - mammary? Debate if it exists in humans. Same as holocrine but pinches off at apex.
Which of the above gland types (#30) is most common in the body?
merocrine
What is the most abundant tissue in the human body?
Connective tissue
Identify the four major classes of adult connective tissue.
Connective tissue proper
Cartilage
Bone
Blood
What is the common embryological origin of all classes of connective tissue?
Common embryonic origin - all arise from mesenchyme
Role of extracellular matrix
What are the two basic components of all connective tissue?
extracellular matrix and cells
What are the two main components of the extracellular matrix?
ground substance and fibers
Describe the composition of ground substance.
Water, CAMS(cellular adhesion molecules), polysachariades and proteoglycans(type and amount present determines property of the matrix)
What is the most abundant structural protein in the body?
Collagen fibers
Which of the fibers is most resistant to tension forces?
Collagen fibers
Which of the above fibers (#40) is found in the basement membrane of the epithelium?
reticular fibers
What cells are found in connective tissue?
blast(immature) and cyte (mature)
fibro-CT Proper
Chondro- Cartilage
Osteo-bone
Hemo-Blood
Be able to identify the -blast and -cyte cell type associated with each class of connective tissue?
blast is immature, mitotic cells, they secrete fibers & ground substance of the matrix, fibroblast, chondroblast, osteoblast, and hemoblast
cyte is a mature, non-mitotic cells, maintain matrix, the exception is hematopoletic stem cells, fibrocyte, chondrocyte, osteocyte, and hemocyte *
Identify and describe the major types of connective tissue proper.
loose CT and dense CT
Which type of the above types serves as a reservoir for water and salts, and accumulates excess fluids, resulting in edema?
areolar CT
What are the functions of adipose tissue?
nutrient storing ability greater than areolar tissue. richly vascularized and metabolic. fat stores, shock absorber, insulation, located in subcutaneous layer
What type of connective tissue proper is associated with epithelial membranes?
areolar CT
Which type of connective tissue proper is found primarily in lymphoid organs?
reticular CT
What is the most widely distributed connective tissue in the body?
areolar ct
What are the differences (structural & functional) between dense regular and dense irregular connective tissue?
dense regular CT is dense, parallel bundles of collagen, wavy, provides firm attachment conducts pull of muscles; reduces friction between muscles; stabilizes
dense irregular CT is collagen fibers running in different places, provides strength to resist forces applied from many directions ; help prevent over expansion of organs such as urinary tract.
Which of the above is found in tendons and ligaments? In the dermis and in joint capsules?
dense regular CT - tendon & ligament
dense irregular CT - dermis & joint capacity
Describe the matrix of cartilage.
matrix is gel-like in consistency
fibers- large number of firmly bound collagen fibers.
ground substance- large amount of tissues
there are no blood vessels, lymph vessels, or nerves in matrix
Identify the location and function of the perichondrium?
Perichondrium surrounds the cartilage. Perichondrium is highly vascularized, dense irregular connective tissue and where cartilage receives its nutrients from.
Identify and describe the differences between the two basic patterns of cartilage growth.
Interstitial growth
Enlarges cartilage from within
Most apparent in initial phase of cartilage formation (during childhood and adolescence)
Appositional growth
Adds new layers of cartilage at superficial surfaces, just under perichondrium
Starts later in development that interstitial growth and continues through late adolescence
Distinguish between the three types of cartilage based on their appearance, fiber, composition, and function.
Hyaline - most abundant, collagen fibers, glassy matrix, supports and reinforces, resists stress, in long bones, costal cartilage of ribs
Elastic - similar to hyaline but more elastic fibers in matrix, maintains shape of structure while allowing flexibility, external ear support
Fibrocartilage - less firm matrix than hyaline, collagen fibers, tensile strength allows it absorption of shock, located in invertebral discs
Describe the matrix of bone.
Similar to that of cartilage but harder and more rigid due to inorganic calcium salts, supplied by invading blood cells with osteocytes in lacunae between fibers
Identify and describe the basic parts of an osteon.
Closely packed structural units formed of concentric rings of bony matrix (lamellae) surrounding central canals containing blood vessels and nerves serving bone
Name and identify the basic structural difference between the two types of bone tissue.
compact - main parts of the osteon:
lamellae (layers of matrix material) form around the central canal
osteocytes sit in lacunae, which lie between lamellae
canaliculi project from lacunae
spongy - matrix is arranged in irregular columns (trabeculae)
spaces between trabeculae are filled with red or yellow marrow
What is the matrix of blood?
Connective tissue developed from mesenchyme and consists of nonliving blood plasma
Compare and contrast the three types of fascia.
Superficial: between skin and underlying organs; areolar and adipose tissue, subcutaneous fascia
Deep: dense, irregular CT, anchors visceral organs in place and compartmentalizes things and very strong; fibrous internal framework
Subserous: between serous membranes and deep fascia; is areolar tissue
What are the two main cell types of the nervous system?
Neurons - branching cells that receive and transmit electrical impulses
Neuroglial cells - supporting cells that protect neurons
What is a membrane?
thin layer of tissue which covers a surface, lines a cavity, divides space or organ
What is a membrane?
thin layer of tissue which covers a surface, lines a cavity, divides space or organ
Located in lining joint cavities and consist of CT only
Located in lining joint cavities and consist of CT only
Why are epithelial membranes considered simple organs?
composed of epithelial layer and underlying CT layer
What are the the three types of epithelial membranes?
Mucous membranes
–line cavities which open to the outside of the body (e.g., respiratory & digestive tracts)
composed of epithelium (may be simple or stratified) over a thicker layer of loose CT (called the lamina propria)
Serous membranes
–moist membranes that line body cavities that do not open to the outside, and that cover organs in that cavity
composed of simple squamous ET which lies on top of subserous fascia
serous membranes consist of
Specific serosa: Pleura
, pericardium, Peritoneum
Cutaneous membrane
-usually referred to as “the skin”
Describe the location and characteristics of serous membranes.
moist membranes that line body cavities that do not open to the outside, and that cover organs in that cavity
composed of simple squamous ET which lies on top of subserous fascia
serous membranes consist of 2 layers
Differentiate between the parietal and visceral layers of serous membranes.
parietal layer lines body cavity
parietal layer reflects back over the organs in the cavity to form the visceral layer
serous fluid is secreted into the potential space between the visceral & parietal layers
What is the function of serous fluid?
serous fluid is secreted into the potential space between the visceral & parietal layers
Describe the location and characteristics of mucous membranes.
line cavities which open to the outside of the body (e.g., respiratory & digestive tracts)
composed of epithelium (may be simple or stratified) over a thicker layer of loose CT (called the lamina propria)
What type of epithelial membrane lines body cavities which open directly to the outside of the body? Which do not open to the body exterior?
mucous and serous, respectively
The skin is considered to be what type of membrane?
cutaneous
Difference between
Pleura
Pericardium
Peritoneum?
Pleura - line thoracic wall and cover lungs
Pericardium - encloses heart
Peritoneum – abdominopelvic viscera
Define lacuna
A small space, cavity, or depression; lacunae in bone or cartilage are occupied by cells
