A&P Embryology (PPT 2)

Gamete

Sex cells. In haploids, the oocyte (F) comes together with the spermatozoan (M) to form a zygote.

Zygote

Fertilization of egg and sperm.

Zona pellucida

The glycoprotein layer that surrounds the egg it hardens once the sperm enters to prevent another sperm from gaining entry (zygote), and leaves after mitosis to allow for growth.

Mitosis

Cell division that eventually forms the morula (2 - 4 - 8 - 16). 16 total cells once complete.

Morula

Ball of cells.

Blastocyst/ blastula

A hollow ball of cells with a blastocoel.

Blastocoel

The fluid-filled cavity of the blastula.

Inner cell mass

A part of the blastocyst that forms the embryo, multiplies and divides into 3 germ layers.

Trophoblast

A part of the blastocyst on the exterior that becomes the placenta (extraembryonic membranes).

Gastrulation

Formation of the 3 germ layers from the inner cell mass.

Epiblast

Portion of the inner cell mass that is closest to the trophoblast. The cavity dorsal to the epiblast becomes the amniotic cavity. Develops into the ectoderm.

Hyploblast

The portion of the inner cell mass next to the blastocoel that becomes the endoderm.

Ectoderm

The outer layer. Forms the epiblast cells. Becomes the epidermis, hair, hooves, epithelium of sense organs, and nerve tissue. Most outer things.

Endoderm

The inner layer. Forms from hypoblast cells. Becomes the epithelium of the gut, respiratory tract, and lower urinary tract.

Mesoderm

The middle layer. Forms from cells between the ectoderm and endoderm. Divides into two layers. Becomes muscle, all connective tissue, and epithelium of the gonads and joints (basically everything not ectoderm or endoderm).

Coelom

The precursor to the body cavities. The cavity that forms between the somatic layer and the splanchinic layer.

Somatic layer

Adjacent to the ectoderm. Gives rise to the bones, ligaments, blood vessels, and connective tissue of the limbs.

Splanchnic layer

Adjacent to the endoderm. Forms the heart, gut muscles, and blood vessels.

Notochord

Develops from the mesoderm. The first support structure that is rod-like. All vertebrates have one. Eventually replaced by the vertebrae of the spine in later embryo (small remnant as nucleus pulposus inside the intervertebral disk.

Neurulation

Ectoderm dorsal to the notochord will thicken, fold into a groove, and meets to form a tube. The dorsal, hollow nerve cord will develop and thicken at the cranial end to become the brain. The hollow is filled with CSF. The spine forms and the peripheral nerves grow laterally.

CSF

Cerebrospinal fluid

Epithelium

Covers the organs (protective), lining, and makes up glandular tissue. Lines the viscera and blood vessels. Secretory cells of glands.

Simple epithelial cell

One layer thick. Allows for the exchange of material.

Stratified epithelial cell

Multiple layers. Used for protection.

Simple squamous epithelium

Single layer of thin, flat cells of irregular outlines. Form continuous, thin membranes.

Squamous

Thin and plate-like.

Endothelium

Simple layer of squamous cells forming the inner lining of the heart, blood vessels, and lymph vessels.

Mesothelium

Simple squamous epithelium lining the body cavities (pleura and peritoneum).

Mesenchymal

Lining of the subarachnoid spaces (in the brain) and chambers of the eye.

Cuboidal

Equal height and width (appear square).

Simple cuboidal epithelium

Widely distributed. Found on the outer covering of the ovary, glandular tissue like the thyroid and kidney tubules.

Simple columnar

Lining for the digestive tract. May be absorptive, secretory, or both. Some secrete mucus for protection. Some are ciliated. Kidney and glands!

Columnar

Taller than they are wide.

Cilia

Motile extension of cell surface. Move tubular contents in a single direction, ie uterine tubes/ oviduct.

Pseudostratified

Appears to be multiple layers but actually has only one. Can be ciliated and non-ciliated. Line the respiratory tract. Globlet cells will provide a wet sirface. Cilia direct the wet surface towards the mouth and traps particles.

Transitional

Stratified epithelium with a varied appearance. Lining of the muscular urinary bladder accommodates stretching. When empty, the bladder will contract, and when full, the bladder will stretch only 2-3 layers. Epithelium has many layers.

Globlet cells

Provide a wet surface (mucus).

Stratified squamous

Used for protection and withstands wear and tear.

Nonkeratinizing stratified squamous

Found on wet surface subjected to wear and tear. Inside of the mouth and esophagus.

Keratinizing stratified squamous

Aka cornified. Cells fused together. Minimizes fluid loss for greater protection. Found on the epidermis (outer layer) of skin.

Exocrine

Secretions of the outside of the body. Have ducts. Originating from the epithelium. Digestive tract.

Endocrine

Secretions within the body. Ductless. Originating from the epithelium.

Holocrine

A gland that accumulates secretory products in its cytoplasm and then dies/ ruptures. It swells then explodes. Ie sebaceous glands (oil/ fatty glands).

Merocrine

A gland that secretes via vesicles so no part of the cell is lost. Ie the pancreas and salivary glands. Exocytosis. Packaging and sending out.

Apocrine

A gland where secretions gather at the outer ends of glands and then pinch off. ie sweat and mammary glands.

Mucous membranes

Line the hollow organs and cavities. Slick. Inside of the digestive tract urinary, and reproductive tract.

Serous membranes

Line the body cavities and related organs.

Pleura

Lining thorax

Pericardium

Lining the cavity outside the heart.

Peritoneum

Lining the abdomen and pelvic cavity.

Connective tissue

Provides mechanical support, a place for metabolite exchange, and energy storage. From the mesoderm and connects one part of the body to another. Have different vascularities. Defined by cells in an extracellular matrix. Chief functions are the production of intercellular substances, storing fat/ adipocytes, and the production of various blood cells.

Loose connective tissue

A variety of cell types. Subcutaneous tissue or superficial fascia. Loose so allows for movement.

Fibroblasts

Produce intercellular substances.

Collagenous fibroblasts

White fibers; strong and inelastic. Appear wavy. Used for structure and proteins.

Elastic fibroblasts

Yellow fibers. Long cylindrical threads or flat ribbons. Regain their original shape after being stretched (like rubber bands).

Reticular fibers

Fine and highly branched. Inelastic. Act as spider webbing.

Amorphous ground substance

Substance without form. Extracellular matrix.

Fibrocytes

Less active fribroblasts

Dense regular connective tissue

Arranged in parallel bundles. Forms tendons. Withstands force in a vertical direction.

Irregular connective tissue

Fibers are interwoven and compacted to form dense matting. Found on the dermis of the skin. Withstands force from all directions. Finers go everywhere.

Muscular tissue

Generates contractile force/ movement

Skeletal muscular tissue

Voluntary and striated. Attached to bone.

Smooth muscular tissue

Involuntary. Non-striated. Make up walls of blood vessels or tubular organs (stomach, bladder, and intestines).

Cardiac muscular tissue

Involuntary, striated, located only in the heart. Can influence heart rate but not actual contraction.

Nervous tissue

Provides transmission, reception, and integration of electrical impulses. Sends impulses through the body, no specific tissue types but specific cell types. Has nerve cells like neurons and neuroglia cells.

Neuroglia

Supporting cells.

Cranial cavity

Houses the brain

Vertebral cavity

Houses spinal cord

Ventral cavity

Cavity divided by the diaphragm. Broken into the thoracic and abdominal cavity.

Pleural cavity

Surrounds the lungs. Divided into two lateral chambers.

Pleura

Serous membrane lining the chambers.

Visceral pleura

Lining the lungs. Lines the side that touches the organs.

Parietal pleura

Mediastinum, costal, and diaphragmatic.

Mediastinal space/ mediastinum

Space in between the two lungs. Partition between two pleura cavities. Contains the heart, thoracic part of the esophagus, trachea, vessels, and nerves. The heart sits here and the trachea and esophagus pass through. Bound laterally by the mediastinal pleura.

Abdominopelvic cavity

Contains kidneys, most of the digestive organs, and the reproductive organs.

Pelvic cavity

Contains the rectum and urogenital system.

Peritoneum

Serous membrane lining the cavity. Lines the abdominal cavity and extends into the pelvic cavity. Lines the entire abdomen.

Omentum

Folds of the peritoneum that pass from the stomach to other viscera. Keeps everything packed in the abdomen.

Mesentery

Folds of the peritoneum that attaches the intestine to the dorsal wall of abdominal cavity

Ligaments

Folds that pass between viscera, other parts of the digestive tube, or connect them with the abdominal wall.